You can find information on how to perform common tasks here.
Loading...
Loading...
Loading...
Loading...
How to get started with software STAR uses.
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Sometimes we stop using things
Loading...
Loading...
Loading...
Loading...
Tutorials that most people would probably need, and don't fit in a specific category
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Tutorials specific to the Airframe Subteam
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Similarly, launch lugs or rail guides
How to prevent the motor from falling out of the vehicle due to gravity or force from an ejection charge
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Current roster of Outreach Activites
Loading...
Loading...
Loading...
Loading...
Loading...
Tutorials for Operations
Loading...
Loading...
Loading...
Loading...
Tutorials specific for the Propulsion Subteam
Loading...
Loading...
Loading...
Adapt this presentation: https://docs.google.com/presentation/d/1U2LXPlMzjgP9DzoBWCuR-Rh4w5Rk6hDWY-4qtUllrYY/edit#slide=id.gb89013080d_0_65
Loading...
Loading...
Tutorials specific to the Recovery Subteam
Loading...
Loading...
Loading...
Loading...
Tutorials for Simulations
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Loading...
Here you can find all the guides on infrastructure, maintenance, and other managerial tasks. These tutorials are mainly for leads and admins.
Loading...
If you're a Berkeley student, you'll have access to a good number of Microsoft and Adobe Software including Premiere Pro.
There are many existing tutorials out there on the web that probably will provide a more detailed step-by-step procedure and description on features of Premiere Pro.
So here, we'll talk about what information you'd want to put in for a club promotional video.
Promotional Videos
Objective
Recruitment: to attract audiences/ potential members to our club
Crowdfunding: to attract donors/sponsors for financial support ex) Crowdfunding
Depending on the objective, what content you want to include in your video will change!
Recruitment Videos
Emphasize the variety of subteams we have (technical AND non-technical)
technical subteams: emphasize projects with short descriptions with minimal jargon
non-technical subteams: emphasize the impact they have/ the non-trivial role they play in the club
present our long term and short term goals so students understand what our team's vision is
Photos
insert images of social activities we have inside and outside the designated club events (i.e. outside of General Meetings)
Clips from our launches are always a crowd pleaser
general tips
sync the audio and the visuals so that the visuals aid whatever the audio recording talks about
transitions look less choppy with 'Cross Dissolve' or fades
Crowdfunding Videos
Emphasize the variety of subteams we have (technical AND non-technical)
technical subteams: emphasize the significance and diversity of projects within the club
non-technical subteams: always include how we aim to give back to the community through education and outreach (not only because we actually prioritize this, but donors love that ;) )
present our long term and short term goals so donors understand what our team's vision is
Photos
Clips from our launches are always a crowd pleaser
As mentioned before, outreach images are also crucial
CADs and layouts/schematics of our projects also spotlight the intellectual value in the projects we do and the knowledge we pursuit.
Including videos of people talking (i.e. interview clip) always adds a nice humanly touch to the otherwise money-hungry typical crowdfunding video
University policy REQUIRES anyone who wish to work at the Richmond Field Station (RFS) for the first time to complete a short online safety training module. The training must only be completed once.
All leads will strictly enforce this requirement. You will not be allowed to go to the RFS if you have not completed the training AND followed all the steps below to submit proof of completion.
Information about the training requirements can be found at the following website, under the section title "Working at the RFS Training Module". Detailed instructions from the page will also be listed below.
Go to this link, you will be prompted to login with your Calnet identity: https://jwas.ehs.berkeley.edu/lmsi?deepLinkActivityId=247519
If the link above does not immediately work, try this link: https://jwas.ehs.berkeley.edu/lmsi
At the UC Learning Center welcome page, navigate to the correct training course by searching for "Richmond Field Station" and selecting the course "EHS 703 Working at the Richmond Field Station".
Start the training, if you are prompted for Organization, enter "STAR", or if you are prompted for a Faculty Adviser, "Ömer Savaş".
After completing the training, you should have a completion certificate. Take a screenshot of it (instructions to take a screenshot), or save it as a PDF.
You have finished the training BUT you are not done yet. You must submit proof of completion using the following form:
You have now completed the RFS safety training requirement!
SolidWorks (also written as SOLIDWORKS) is a 3D Computer-Aided Design (CAD) program. STAR uses SolidWorks for a large portion of our design work.
SolidWorks is only available for Windows 7, 8, and 10.
If you have a UNIX-based operating system on an Intel/AMD chip, consider dual-booting Windows (see Boot Camp for macOS) or running a virtual machine (the campus provides VMware and a Windows license for free).
You can also use Parallels for macOS or VirtualBox for Linux. Refer to the VMware/Boot Camp setup page for more detailed instructions.
If you have a Mac with an M1 or M2 Silicon processor, you must use Parallels for macOS as Boot Camp is unsupported on these Macs.
You can also attempt to use other means to access a Windows installation like Chrome Remote Desktop.
Before starting, make sure you have a fast, reliable internet connection and enough space on your disk. This process will download roughly 8GB of data.
If you are upgrading from an older version of SolidWorks, do not delete the old version and then download the new version. The old version can be upgraded.
STAR is migrating to the SolidWorks 2023 Student Edition.
Go to: www.solidworks.com/SEK and complete the form (first name, last name, Berkeley email address, select “student team” on dropdown)
Under product information
Select Yes (I already have a serial number)
Choose 2022-2023 version
The serial number is listed in the discord server under #info
Check the #info channel in the club discord for the serial number.
The download link only downloads a ~32.1MB file named SolidWorksSetup.exe. A 7.1GB-18GB download will take place after following the instructions in the installer if a new installation is made.
Make sure you only install Solidworks, and not any of its extra add-ons like Solidworks Electrical. People have had problems in the past when trying to install extra add-ons.
If presented with the option above in the installer, it is recommended to upgrade rather than create a new installation to save space.
On the summary page of the installer, you can select which products you wish to install. At minimum, you will need the 7.1GB SolidWorks package.
Instructions on downloading and installing SolidWorks Student Edition 2023 can also be found here.
If you need more help, this video can help walk you through the process!
For those of you with M1 and M2 Macs, this video can help you with the process. This website may also help. You will need to download Parallels to run Solidworks in a Virtual Machine on your Mac.
You should now have successfully installed SolidWorks! If you encounter issues, please contact a lead before moving on. Uninstalling, rebooting, and trying again can resolve many issues. Now that you've downloaded SolidWorks, head on over to Our SolidWorks Training Tutorials and some of our previous Training Sessions to learn how to use it! You can also learn more about our file-sharing platform here!
How to get paid back after buying stuff for the team.
STAR is a Registered Student Organization under the Associated Students of the University of California (ASUC). As such, our funds are stored in their accounts and must be paid out according to their policies. Probably for better documentation and to ensure all money is spent properly, they only disburse funds after we purchase the items. This disbursement is your reimbursement.
Note: This process has changed to be entirely online since March 2020
Only members can submit a purchase request. In the eyes of the ASUC, our official membership list is on our CalLink page. The following steps will show you how to get on our CalLink roster.
First, go to our CalLink page here: https://callink.berkeley.edu/organization/star/. Sign into your Berkeley account and click Join to request membership. This is a one-time thing, and will allow you to submit a Stage 1 Purchase Request.
You will need to wait for a lead to approve your request to Join. The finance tab will not be available until you are approved. Leads, you must manually mark approved members as "Financial Requestor - 1st Stage" in CalLink for the Finance tab to appear.
We have noticed that the "Join" button is missing sometimes. If that happens to you, just send a message in the #business channel or dm the business lead for a "financial requestor--stage 1" status, along with your Berkeley email and name.
Once you have been approved as a member, again, navigate to our CalLink page: https://callink.berkeley.edu/organization/star/. You should see the following page:
Then, click the STAR icon on the left banner. The icon will turn into a gear when the mouse hovers over it. This will open a sidebar. Click the Finance option.
The screenshot here shows what an admin (usually a lead) can see. If you are a 1st-stage financial requestor, you will only see Documents and Finance on the popped-up menu.
If you do not see the banner, you may be using the old Callink web page layout. Refer to Navigating the old Callink web page layout if this is the case.
Click the Create New Request button and then Create New Purchase Request from the drop-down options.
Fill out this form as accurately as possible.
The PR form asks for your UID. It is NOT your student ID on your Cal One Card. Be sure to follow the instruction on the PR form to look up your UID. We recommend right-clicking the UID link, and opening it in a new tab so that you won't lose progress (if you click on the UID link directly, it may just reload the current page into the new page)
For Subject, use the format [full name] - [subteam] - [item description]. For example, this might look like:
Rajiv Govindjee - Propulsion - Test Stand Hardware
The description of items in the Subject should be brief but descriptive; try to use between 2-5 words. You can elaborate below in the Description field as well.
Enter the Requested Amount; this should be the total for the purchase request. Purchase requests (PRs) are usually one item, but you can theoretically put up to six items on a single CalLink PR.
For Categories, chose Reimbursement - Any amount. If you feel like you must use one of the other categories, please reach out to the Business lead.
Refer to the table below for Account:
As of now (May 24, 2022), all expenditure, regardless of categories, should use our misc account: 3-70-203828-00000-MISC-STAR
.
Fill out the Payee Information completely. If you are getting a check mailed to you, this address is where it will go.
Select an expenditure action
Check out the following chart for more information about three common actions:
We recommend Mail to Payee-same address or Direct deposit
For most cases, you can leave Special Instructions and Event Details blank.
Fill out the required fields for Item #1 (Date, Type, Vendor, Location, Total)
The form asks you to attach receipts: failure to do this will mean the request is rejected. Below is a sample procedure to reliably get your PR approved:
Only complete Step 3-7 if your receipts do not have billing contact (name, address, etc.).
Download or scan and upload an invoice or receipt from the vendor. For Amazon, invoices must show the word "Shipped". For McMaster, it's best to concatenate the Receipt and Packing List (shipping confirmation), but you might be able to get away with just the Receipt (as long as it shows shipping cost).
Redact the invoice/shipping notification as appropriate.
Download a PDF of your credit card / bank statement (and make sure it's not password-protected to edit; you can use "Print to PDF" from your browser if this is an issue).
Use a tool like Adobe Acrobat DC (free for students at https://software.berkeley.edu/adobe-creative-cloud) to redact sensitive information like routing numbers, other purchases, balance, etc. (optional, but recommended).
You will need to leave your name, dates, amount of relevant purchases, and the last 4 digits of your card number _unredacted._ The ASUC can and will reject PRs without this information on your statements.
Verify the invoice total matches the credit card statement total. If it does not, the ASUC will likely reject your request.
Verify the Payee name matches the bank/credit card statement. The ASUC will likely reject your PR if this is not the case. It may be acceptable to have no name on the reciept, but not one that does not match.
Use a tool like Adobe Acrobat DC to concatenate the invoice and statement into one file, omitting any irrelevant pages.
Upload the file.
Repeat the process for Item #2, ... , 6 if applicable. Most PRs contain only one item.
Once complete, check over all your entered data. Upon PR submission, you cannot edit the PR anymore.
Submit the Purchase Request.
Once you have submitted the PR, your job is complete! STAR's stage-2 financial agents, who are usually in the business subteam, will approve your PR or contact you for further questions! If you realize that you have made a mistake, please inform the agents. You can do that either by direct messaging or sending the message to the Business channel in STAR's Discord Server.
If no stage-2 agents approve your PR or contact you after 3 business days, please send a message in the Business channel.
If some of your receipts do not have billing contact (name, address, etc.), which can clear show that they were your purchases, you should prepare a digital copy of your credit/debit card statement proving you paid for these items. (you can redact all irrelevant information, but make sure to leave your name on the statement)
Only follow the steps below if for some reason you were not able to upload the necessary documents to the purchase request, and they have not been added even after the purchase request is Stage 2. We recommend you to complete this step with a Business member
Please e-mail proof of payment (credit card statement or bank statement) to asucfinance@berkeley.edu. The email must include:
The purchase request number in the subject line
The name of the payee
A finance representative from the team will review your request and elevate it to a Stage 2 request. We will check that the amount requested matches the amount on the proof of purchase, and we will check that you have all required proof of purchases.
Once approved, you will be notified through email or Discord. You can also check status from the Finances page.
If your request does not meet our requirements, it will be rejected. Please check this page to make sure you met all the requirements.
Wait for approval from the LEAD Center. They may reach out to you for more details. If your PR(s) are listed in Stage 5, that means your reimbursement(s) have been approved.
Once you have been approved as a member, again, navigate to our CalLink page: https://callink.berkeley.edu/organization/star/. Click Manage Organization in the upper right corner.
Then, click the expand menu button (three horizontal bars) on the upper left corner . This will open a sidebar.
Click the Finance option.
Click the Create New Request button and then Create New Purchase Request from the drop-down options.
Now you are ready to resume the tutorial above. Click here to return.
If you are buying... | Use this Account |
---|---|
Expenditure action | What does it mean |
---|---|
Any hardware for vehicles, engines, or related projects
3-70-203828-00000-MISC-STAR
Social supplies, outreach, etc.; non-hardware purchases
3-70-203828-00000-MISC-STAR
Mail to Payee-same address
No additional set up or office visit needed. However, it takes several days for checks to be mailed to the address indicated in your PR form.
Direct deposit
Electronic deposit, the fastest way to receive reimbursement, but requires additional setup. For more info please check out Section 6A in the PR form
Pick up
No additional set up required; however, you would need to visit 432A Eshleman Hall with a valid photo ID
3D model file-sharing!
Starting this year, STAR will be using SolidWorks PDM for version control and file sharing for 3D models. Once everything is set up on the server side, we will update this page on how to access PDM and get it set up!
How to install and run OpenRocket with as few issues as possible.
OpenRocket is an application that uses Java (Version 6 or later) to run. Mac OS generally comes with Java and will update it automatically. For Windows machines you may have downloaded Java for some other application already. To download the most recent version of Java, click here.
OpenRocket is free to download and is available here. Once at the site, click to download the most recent version. The download should be fairly quick and you can run the file immediately once downloaded, so long as Java is installed.
If you have any issues with running OpenRocket, or just want a slightly easier and improved experience, Neil W.'s post on The Rocketry Forum hopefully has you covered. Read the post for more detailed information, or simply get started in OpenRocket by downloading and running from the links below.
https://www.dropbox.com/s/dfpo0pzztgsscqf/OpenRocket-15.03-installer.exe?dl=0
https://www.dropbox.com/s/33o53vlle5b0uex/OpenRocket-15.03.dmg?dl=0
ANSYS Student is an ANSYS Workbench-based bundle of ANSYS Mechanical, ANSYS CFD, ANSYS Autodyn, ANSYS SpaceClaim and ANSYS DesignXplorer.
To download ANSYS Student, navigate to https://www.ansys.com/academic/free-student-products. Scroll down and select ANSYS Student, then click on the Download ANSYS Student 19.1 button that appears below.
After the folder finishes downloading, unzip it with your favorite unzipping tool and navigate to the new folder. Then, open a file found inside the new folder labeled Setup.exe. Click the Next arrow in the bottom right corner as you progress through the setup. Once installed, you can open ANSYS by searching "Workbench 19.1" in your computer's start menu.
We have experienced an issue once where the workbench application did not install. In this case, delete the ANSYS program file in your C drive and repeat the process above.
This is specifically for Macs
Do this BEFORE any part of the solidworks tutorial if you do not have a windows operating system
This will only work for Intel-based Macs, not for M1 and M2 Macs. For those, you will have to download Parallels. This video will help show the process.
If you've already downloaded SolidWorks onto your mac, just delete it until after you have completed this tutorial.
VMware is a software that is free for Berkeley students that allows you to run windows on a non-windows computer which will allow you to install and run SolidWorks. Bootcamp is a program native (already downloaded) on macs that also allows you to run windows on a mac. Both options have some pros and cons which will briefly be detailed below. If you already know what you want to use, skip to the directions. If you have any questions/problems with the directions feel free to contact Ananya Subramani on the STAR Discord.
Allow you to run the latest version of Windows
Can run SolidWorks
VMware is easier to start up (like starting up a browser or generally opening up an app)
Boot Camp requires you to restart your computer whenever you want to run in a windows environment
Boot Camp requires you to permanently partition your hard drive which cannot easily be changed after it is done.
Partitioning your hard drive here means that some amount of your drive will only be accesible to the windows boot and the rest will be accesible normally
Main thing here is that you can't get more memory/storage if you need it in the windows portion easily
VMware does not require a permanent partition so the size can change
Boot Camp will run SolidWorks more smoothly because all of your RAM can be used
VMware will be able to run solidworks, but it may not be as smooth because you won't be utilizing all of your RAM
My personal reccomendation is to use Boot Camp if you plan to use solidworks very actively, and VMware if you just want to look at files in more detail than grabcad shows. If you have a lot of RAM though, you could probably just go with VMware and be fine
You will need the following things, or the download will probably fail at some point:
Mac made in 2011 or later
exception: 2012 Mac Pro “Quad Core” using the Intel® Xeon® W3565 Processor
OS X 10.11 El Capitan minimum required
You can check this using the "About your Mac" tab in the top left corner apple drop down menu
>50 GB free storage
Start by going to this website: https://software.berkeley.edu/microsoft-operating-system and taking the link for "personally owned devices." You should be able to navigate to this screen:
Click on Windows 10 and add it to your cart. If you want to use VMware, go to step 2.5, if you want to use Boot Camp, check out and go to step 3.
From the same place you should be in step 2, go to the VMware tab and download VMware Fusion 11.x (for Intel-based Macs). You should get to this screen:
Add VMware to your cart and check out.
In the details of your purchase that you made in step 2, there should be a windows license number, you will need that.
My screenshot doesn't have a Windows license number because it's been more than one month since I "bought" it but yours should.
Once you have access to that license, navigate to this site: https://www.microsoft.com/en-us/software-download/vlacademicwindows10iso
Select the proper language, and download the 64-bit version
VMware users, go to step 4, Boot Camp users go to step 5
Download VMware fusion from the cart and open and install the application. When it asks for a number during the setup process, enter the serial number that I blacked out in my screenshot.
Once you see this screen, drag the windows 10 iso file into the place where it says install from disc/image (the default name for the downloaded file is shown below)
From here, just go through the installation steps and once you have your virtual machine configured and you can access the internet, go back to the solidworks installation guide and follow those steps *in* your virtual machine.
Using the spotlight search or some other search bar on your mac look up "Boot Camp Assistant" and open the app. You should see the following screen.
From here, hit continue and you should be able to choose your partition size, with the minimum being 42 GB, which should be fine, but if you are willing to dedicate more space to a Windows partition, go for it.
Once you've completed the installation process, you can boot into your windows partition by restarting your mac while pressing the "option" key.
Once you are in your Windows partition, you can go back to the SolidWorks installation guide and download SolidWorks.
Straightforward version control for CAD
GrabCAD Workbench is an online platform to share CAD files and collaborate on projects, featuring version history tracking. It integrates directly with SolidWorks with a toolbar add-in and a desktop application.
If you already have a GrabCAD account, you can skip this step.
GrabCAD Community and GrabCAD Workbench accounts are the same
Creating a GrabCAD account is a straightforward process, first naviagte to:
In the company details section, choose job level as "Student" first before filling anything else out. The company name section should change to school name; type "University of California, Berkeley" (or some variation thereof) in the text box.
Proceed through the signup process.
Be sure to go to your email to confirm the account.
You've now successfully created a GrabCAD account!
Message the email you used to sign up for GrabCAD to the Operations Lead (@mcelly#1609) along with a copy of the previous paragraph on naming to obtain an invitation to STAR's GrabCAD page. Let them know which projects you need access to, if possible.
The GrabCAD Workbench desktop application allows you to sync CAD files from your projects so that you have a local copy on your computer. It also installs the companion SolidWorks toolbar.
Navigate to the following link to download the installer:
Continue through the installation process. After completing the installation, be sure to log in with your GrabCAD account.
You've now successfully installed the GrabCAD Workbench desktop application!
How to Connect to CalSTAR's Server for Maintenance, Solidworks Workgroup PDM or Converge CFD Licensing
As of August 14, 2018, CalSTAR's Microsoft Azure Server has been taken offline indefinitely. The server's primary role was to serve as a PDM host, a task taken over by GrabCAD. Its secondary task of hosting Converge CFD license validation was deemed to not be valuable enough to justify continued payment for the server.
In order to use Solidworks Workgroup PDM or Converge CFD, you must be on the same network as our server. Since we cannot physically connect to the same wifi or ethernet connection, we will be setting up a Virtual Private Network (VPN) to link your computer and the server.
As a very generalized example, you can think of a network as a small town, with roads connecting houses and stores. Being in the same town (network) allows you to use the roads to go from your house to the store and back (exchanging files and information with the server).
Staying with this example, a separate network would be the equivalent of a town on the other side of a river. The two towns can not interact with each other. You cannot drive from one town to the other, a home in one town cannot visit a store in the other.
This is representative of your computer and the server right now. The server cannot interact with your computer, and your computer cannot interact with the server. To have any interaction between the two towns (your computer and the server), a physical connection must be made. In our example, this would be the equivalent of building a bridge across the river. You must plug your computer into the same internet (ethernet/wifi) as the server. This is not possible since Microsoft owns the server and it is probably miles away from you.
What we will be doing in this guide is setting up a Virtual Private Network (VPN). In our two-town example, the VPN is basically a quick and temporary bridge connecting the two towns. The VPN will make it seem as if the two towns are one, connected with the same roads. This lets the server communicate with your computer and vice versa. This is necessary in order to share files between the computers (essentially what the PDM and license check does).
In order to set up the VPN with our server, you must install a VPN Client. The following two programs have been known to work well:
Choose one and download the version for your operating system. Read the notes below for your chosen program.
Configuration files for both programs can only be downloaded when signed into Google Drive with a berkeley.edu account.
Make sure you are downloading the SoftEther VPN Client under Select Component
When installing, make sure you are installing SoftEther VPN Client and NOT the Manager (Admin Tools Only)
Proceed with the rest of the installation.
Launch SoftEther VPN Client Manager
Select Virtual Adapter at the top of the window, then New Network Adapter
Click OK (Name should be prefilled as VPN)
Once finished, click Connect at the top of the window, then Import VPN Connection Setting...
Locate and import the 'pdm2.vpn' file you downloaded earlier (probably in your downloads folder).
Select the new connection PDM2 and login with the provided credentials.
When installing, leave the default options checked (select them if unchecked):
OpenVPN User-Space Components (grayed out)
OpenVPN Service
TAP Virtual Ethernet Adapter
OpenVPN GUI
Options in Advanced can be modified as you wish
Configuring After Installation
Launch OpenVPN GUI
For Windows, after starting OpenVPN, the OpenVPN GUI shows up as a computer-with-lock icon in the system tray (icons near the clock and date)
Locate the OpenVPN GUI icon in your system tray, and right click it.
Select Import File...
Locate and import the 'pdm2.ovpn' file you downloaded earlier (probably in your downloads folder).
Click OK
Right click the OpenVPN GUI icon.
Select Connect and login with the provided credentials.
STAR parts currently follow the set naming convention outlined at found under Tutorials --> Operations --> SolidWorks file conventions. All parts in STAR GrabCAD projects created after 2019 must follow this format. If you have questions, just ask in #operations!
You may want to unsubscribe from Workbench emails here (there are a lot!):
SoftEther VPN Client [] []
OpenVPN [] []
You only have to do this once! Follow these instructions carefully and everything will be easier later on.
Before moving forward, make sure you have GrabCAD set up in SolidWorks:
Open up SolidWorks
Make sure that your local GrabCAD folders are up to date
If you don't know how to do this, check out: Using GrabCAD Workbench in SolidWorks
Navigate to Tools>Options
4. In the popup window, navigate to "File Locations"
5. Click "Add"
6. Navigate to the top-level GrabCAD folder "IREC18 Templates"
7. Press OK
Now, when you make a new part, this will show up! You can navigate to the IREC18 Templates Tab and select that drawing template when you make a new drawing.
If you don't see this dialogue, click on "Advanced" in the bottom left corner
You're all set! Now when you make a new part or drawing you should be able to navigate to the IREC18 Templates tab and make a new part just like you would normally.
When you create a part, you can still use the default part template (i.e. just make a part however you would normally). This is only relevant for creating drawings.
Some properties in the title block will be automatically filled. We have already determined which ones will update automagically, so all you need to do is the following:
Double click the title block
Some fields should be highlighted in blue
Edit the blue text boxes
Click outside of the title block
And you're done! It's that easy!
At the time of writing this, the GrabCAD SolidWorks add-in is not supported for SolidWorks 2019. You will still be able to change and sync local files to GrabCAD projects, albeit less conveniently.
Before starting, make sure you have completed your installation of GrabCAD Workbench. If you have not, please finish the instructions here:
Upon being added to CalSTAR on GrabCAD, you'll be able to see all our projects.
In order to access these projects locally, first create a folder anywhere in your existing files. (When you downloaded GrabCAD, it by default should have created a "GrabCAD" folder in Documents.)
While the name of the folder does not matter, for clarity, you should name it with the same title as the GrabCAD project you are trying to sync to.
In the GrabCAD Desktop App, you'll have the option of manually connecting a project. Select that option, select a project, and link it to your recently created folder.
In the Desktop app, if you have successfully connected a project to your local folder, you'll be able to see the status of both the local folder and the online Workbench. If the Workbench panel is blue, that indicates that other people have made changes to files within the project and you will need to download these updates.
If the Workbench panel is black and not blue, you do not need to do anything and are completely up to date.
Hover your cursor over the Workbench panel and click to download.
Make sure all changed files are selected and click Download Selected. After all of the updates finish downloading, you should see a green box pop up both in the Desktop app and in the bottom right corner of your screen that says the downloads have finished.
To open a file for use with GrabCAD, click on the Open Folder button in the Local Folder panel, then double click on the desired part in the pop-up file browser. Other methods of navigating to the part are not guaranteed to work (although they may if your files are reasonably organized and you know for certain you are accessing a GrabCAD synced file).
Before working or making any changes to a file, first lock the part in the online GrabCAD Workbench by navigating to the part and right clicking. More documentation on locking can be found here.
If you do not lock the file you are working on, you may create file conflicts and lose changes!
Work on the file for as long as necessary. It is good practice to save and upload with every major revision, even if you will be working for quite a while on the same part.
It should not require SolidWorks crashing and you losing all your progress in order for you to learn the importance of saving often.
After saving the file with changes, we are now ready to upload. Save the file and return to the Desktop app. You should now see that the Local Folder panel is highlighted blue. Hover your cursor over the panel and click to upload.
In the upload tab, you will be prompted to include a comment describing the upload. Write a descriptive message detailing exactly what you have changed since the last version.
When you are done with this, press the Upload Selected button to complete the process (by default, all changed files should be selected). As before, a green box will pop up notifying you when the upload is done.
If you don't plan on making any more edits in the current session, go back to the online Workbench and unlock the file by right clicking.
You're all done. Again, make sure to unlock the file when you're all finished editing it!
So you've downloaded SolidWorks, now how do you use it?
We are going to provide different tutorials based on how experienced you are at SolidWorks and 3D modelling in general.
Absolute Beginners
The rest of the tutorials we are about to provide are based on which specialty you are joining!
Airframe/Recovery Tutorial Links
Avionics doesn't really use SolidWorks, but we are working on getting PCB design Tutorials!
Payload Tutorial Link
Propulsion Tutorial Link
Simulations Tutorial Links
Some of these videos will be cross-disciplinary, so if any of them catch your interest, give them a watch and practice them!
You should now know at least the basics of how to use SolidWorks! Just keep in mind, the best way to learn is to practice, so boot up SolidWorks and get to it! (Tip: Always keep a mouse on you if you plan on using SolidWorks! It makes it a million times easier.)
How to make those cool parts that you designed; or, how to design cool parts that are make-able
Broadly speaking, this section covers how to select materials, how to manufacture parts out of stock, and how to choose / work with parts that you cannot manufacture yourself.
If you're just getting started, we recommend going through the 3D Printing and Laser cutting tutorials; refer to the Material Properties and Uses page as needed:
If you have more experience or are a little farther along in the design process, check out some of our other tutorials on how to use commercial parts or where to source stock from:
For more specialized needs, we have a few tutorials on more advanced manufacturing methods:
The FabLight is a laser cutter designed to safely cut both metal sheets and tubes.
The FabLight is more precise than a water jet and has a less steep learning curve. In a non-COVID year, it is also more available due to being located in the general all-purpose makerspaces (studios 110 and 120) and not the metal shop with its more limited hours. For Jacobs Project Support during COVID, the FabLight similarly has a faster turnaround time and can produce parts more quickly once a request is received.
The disadvantage is that the FabLight of course cannot cut through as thick materials as a water jet. The maximum thickness that a STAR member has previously cut through on the FabLight without issue is 1/8" stainless steel.
November 2020: The Payload subteam successfully laser cut leaf springs for the Bear Force One payload structure out of 1/32" 6061 aluminum, available through the Jacobs Material store.
For more information about the process of using the FabLight (e.g., preparing and loading a file/CAD drawing) and a full list of approved materials, please visit the . In a non-COVID year, both the online quiz and in-person training is required prior to being able to use the FabLight.
One of the most common ways to produce low-cost, quick-turnaround parts out of thermoplastics.
The term "3D printing" is most often used to refer to fused deposition modeling, or FDM. There are other less common / more expensive methods of 3D printing (stereolithography and selective laser sintering), but those will not be covered in this guide. Generally, all of these processes fall under the umbrella of "additive manufacturing". Here is a description of the FDM process from Wikipedia:
Filament is fed from a large coil through a moving, heated printer extruder head, and is deposited on the growing work. The print head is moved under computer control to define the printed shape. Usually the head moves in two dimensions to deposit one horizontal plane, or layer, at a time; the work or the print head is then moved vertically by a small amount to begin a new layer.
To illustrate the basics, here are some graphics:
While 3D printers can attempt most kinds of geometry, you will achieve far more success by considering the printability of your part during the design process. In addition, some parts are simply infeasible to print.
We recommend adding 0.010" - 0.020" or 0.3 - 0.5 mm of clearance between parts that you would like to fit together. Some printers extrude more than others, making this often an iterative process.
Printed parts are anisotropic, meaning they have different properties along different directions. This is a direct consequence of the fact that they are built up layer-by-layer.
Printers generally have different resolutions in different axes. Usually, the x-y resolution is far greater than the z-resolution; after all, the z-resolution is limited by the height of each layer.
Do not attempt to use a standard FEA simulation for anything more than a broad evaluation of a printed part. Printed parts almost always fail along layer lines (i.e. one layer separates from the next one up) and not within a layer. As a result, printed parts are often much weaker than expected in in the z (normal to layers) axis and with respect to bending moments in all directions.
This step is highly machine-dependent.
Most parts require some sort of post-processing.
Removal of supports is an exceedingly common task, but also a frequent source of injury. Here are some tips.
We recommend using your hands or needle-nosed pliers for the removal of supports. Do not use any sort of blade if at all possible. However, if you need to remove a brim or clean up a burr, we highly recommend the use of a deburring tool. These are fairly safe and extremely effective; use by gently pulling the tool toward yourself.
If you cannot find a deburring tool (STAR generally has one, as does Jacobs), you may use a knife as a last resort. We recommend using a 2-3 in-long folding or fixed-blade (where legal) knife with a locking blade. In the absence of a locking blade, a swiss army-style knife is acceptable. We strongly advise against using an X-Acto knife for this purpose, even though they are commonly found in maker spaces.
When using a knife to clean up a part, always CUT AWAY FROM YOURSELF AND OTHERS.
Use long, smooth strokes and do not attempt to force the blade. If the blade becomes stuck, just back out and try again with a more gentle angle/less pressure. Try to limit the use of a knife as a prybar; use pliers when possible. Again, CUT AWAY FROM YOURSELF AND OTHERS.
The advantage of printed parts is that it is usually possible to rapidly iterate on them to fix fit issues. That being said, it is often useful to remove a small amount of material to allow two parts to fit together. We recomend the use of files, not sandpaper whenever possible. Files will remove material far more quickly, at the cost of some flexibility.
While it may seem possible to sand down printed parts to achieve a smooth finish, this is almost always a colossal waste of everyone's time. Only do so if absolutely critical. Be warned that the plastic will likely appear to whiten a bit as the sanding abrades the surface.
You may use a thin, clear epoxy to coat parts for protection and aesthetics. We recommend using a disposable foam brush and an epoxy with a long enough working time that it does not get sticky while being applied. This method may also work together with sanding (see above).
If you have an ABS part, it is possible to smooth the surface using acetone vapors. Here is a link to a reasonable tutorial. Do NOT follow a tutorial making use of a hot plate, stove, etc; this is unnecessary and dangerous, risking a safety incident to save an hour or two. Without heat, this is generally a safe process. Be warned that the acetone vapors may compromise the structural integrity of your part over time; watch for cracks and increased brittleness. There are no reasonably safe solvents that can smooth PLA parts; the only such chemicals are designed to attack organic matter and are thus highly toxic to humans. Do not attempt to acquire them.
What good is MSE anyway?
Delrin is a low-friction plastic that is extremely machineable; Delrin parts can be made on a laser cutter or mill. For small, precise parts, the Othermill is a great way to machine Delrin. Delrin is fairly strong, although it will deform substantially under higher loads.
Acrylic (in the form that Jacobs Hall sells) is a fairly brittle material that we recommend avoiding for use in flight parts. Acrylic is occaisionally useful for enclosures or signs. Polycarbonate is recommended as a substitute for acrylic unless the material must be laser cut.
This is the material we are currently using for our thrust chamber. Otherwise, generally avoid brass as there are better and cheaper substitutes available (usually aluminum).
Jacobs Hall sells plywood in several sizes and thicknesses for laser cutting. Common thicknesses are 0.25 in and 0.125 in. It is important to note that wood is anisotropic; its material properties vary significantly according to the direction of the forces applied. Wood can be used for structural parts, but it may be better to consider Lexan and aluminum first. Jacobs plywood is often used to make non-structural jigs, holders, etc.
Lexan is extremely strong, although it will flex slightly under load. Most of our Lexan parts are produced with a waterjet cutter, although they can be milled, bored, etc. afterward if needed. We are unable to cut Lexan with lasers; if laser cutting is desired and strength is not a priority, consider using Delrin instead.
PLA is a bio-based plastic commonly used for 3D printing. It is slightly more brittle than ABS, but it can absorb more energy before failure. See the "Acrylonitrile Butadiene Styrene (ABS)" entry for a comparison of PLA with ABS. It is also more readily available than any other 3D printing materials in the Jacobs Hall Makerspace. PLA is a good candidate for parts with complex geometry that are non-structural in nature. It is important to note that printed parts, like wood, are anisotropic; they fail much more easily in some directions (along layer lines) than others.
ESRA guidelines say we pretty much can't use stainless steel for anything important. That being said, other projects or non-critical parts might be allowed to use stainless steel; check the regulations! Many low-strength fasteners are made out of 18-8 stainless.
ABS is a common 3D-printing plastic. It is slightly more ductile than PLA, the other common printing plastic, but otherwise . While there is a common perception that ABS is "stronger" than PLA, this is somewhat inaccurate; for most uses, they are indistinguishable.
6061 aluminum is a fairly machinable material that can be processed with a waterjet cutter, bandsaw, fiber laser cutter, mill, lathe, and/or welding machine. Compared to most plastics and wood, aluminum is very strong; consider using aluminum for parts where strength is more important than weight. Aluminum is fairly soft, so do not design parts that require threads to be cut into aluminum; instead, use . We generally use the 6061 alloy, but others are acceptable; check with an expert before making the decision to use another alloy.
ABS | PLA |
ABS printers at Jacobs have soluble supports | Usually not available with soluble supports at Jacobs |
Much higher tendency to warp, especially without enclosed, heated build envelope | Doesn't warp nearly as much |
ABS printers at Jacobs are much higher resolution than the Type A / Ultimaker | Type A prints are typically the worst quality achievable, Ultimakers are slightly better |
Parts may bend instead of breaking, higher elongation at break | May crack if dropped, rather than bending, but higher tensile strength |
Dimensions and Fortus are limited and often in use, may require joining a lengthy queue | Type A and Ultimakers are more plentiful and more frequently free, with low turnaround time |
Free at Jacobs |
Fumes may give you cancer, kills the planet | Food-safe, biodegradable (with 6 months in a specialized composting facility, don't worry) |
Gets softer at slightly lower temperatures |
Requires Jacobs hands-on training | On-line training only needed |
Little ABS personally owned by team members | In-stock at homes of team members for printing |
A way to selectively remove material from a piece of stock
Contrary to popular belief, a mill is not a drill press. This is a manual mill:
A mill has a spindle which holds an end mill. End mills are similar in appearance to drill bits, but are not the same!
The spindle spins the end mill rapidly while the material (or the spindle) is moved in the x, y, or z directions. More advanced, usually computer numerical control (CNC) machines can also sometimes rotate, giving up to 4 or 5 "axes" to move in. With CNC milling, a computer, rather than a human machinist, handles the motion of the stock and spindle. Here is an example of a CNC mill in action:
Both manual mills and CNC mills generally share some basics in terms of how they operate. Here is a video that covers the basics of mills:
Just like drill presses, mills can make holes in materials. You can either use an end mill, or simply put a standard drill bit in the mill using a removable chuck. Mills are particularly useful if you would like a set of very precisely spaced holes, as they possess an x-y coordinate system (drill presses generally do not).
In the image above, notice that the center hole is not bored all the way through. This is generally possible to do fairly accurately even on a manual mill, with the use of a stop. However, dimensional accuracy may vary. Always check with your machinist first.
In the US, drills come in number sizes (smallest useful size being #50-#60 and going all the way up to #1, which is roughly 0.228 in) as well as letter sizes, which start at A (0.234 in) up to Z (0.413). Beyond and interspersed with the letter and number drills are standard fractional inch size, ranging commonly from as small as 3/64 in up to 1 1/2 in. Check with your machinist to see what sizes are available first.
A mill can remove material from a face or create a flat surface at any depth. Furthermore, sharp corners are possible if the tool is allowed to travel off the end of the part (see Pockets section for examples of when this is not the case). It is best if these cuts are at right angles to each other; more complex geometry will require the use of CNC.
For an example video of a CNC machine cutting a more complex profile, see below:
When a flat surface with some type of wall on the sides is desired, we have a pocket. Mills are able to do pockets, but keep a few things in mind:
End mills (the tool) have finite radii. For example, if an 1/8" diameter end mill is used to make a pocket, the interior corners will have a minimum 1/16" radius. Use a fillet in CAD to reflect this.
Conventional (manual) mills may not easily be able to make, for example, a rectangular pocket with precise corner coordinates, especially if the pocket is deep and requires multiple passes. This type of geometry is better suited for a function mill or a CNC mill. When in doubt, check what can and cannot be done with the person who will be making the part!
This type of geometry will generally only be possible with a CNC mill. Please be aware that CNC parts can have long lead times if coming from the machine shop. Furthermore, there are still limitations on what a CNC machine can do; as with manual mills, there are limits based on available tooling (curved surfaces generally require ball end mills) and the material.
Try to limit the number of different tools needed to make your part. Tool changes can cost significant time and effort. For example, try making all holes a standard diameter, or choose just a few. If a pocket is large, use large-radius fillets on the corners to allow the machinist to use a single large tool to make the feature in one pass, rather than switching to a smaller tool just for the corners.
When in doubt, ask. Other club members or the machine shop staff are happy to help!
This manufacturing guide takes you step-by-step from a SolidWorks model to a laser cut part.
Laser cutting is a fast manufacturing and prototyping method suitable for highly planar parts.
Start by opening the SolidWorks part you want to laser cut.
Select the surface that you want the laser cutter to follow by clicking on the surface, as shown in the image below.
In the top menu, go to "File">"Save As"
From the file type drop down box, you must select a DXF (.dxf) file
Click "Yes", and a properties box will appear on the left sidebar. The selected face should be automatically filled in the "Entities to Export" box. Click the check mark and then "Save" to proceed.
We are now done with SolidWorks, but before exiting the program please take note of the dimension units of the part. In the part above, it is in inches (IPS)
Now open Adobe Illustrator, click on "File">"Open" and select your .dxf file.
A very important window will pop up. Under "Artwork Scale" you must select "Scale By: 100%" the "Scale" box must be 1.
Now, remembering what your part dimension units were, you must select the correct units you used in SolidWorks in the "Unit(s)" box. For IPS, select "Inches" from the drop down and for MMGS select "Millimeters".
After selecting the unit, the value of the "Unit(s)" box may change. This value must be set to 1.
Have you ensured that your DXF scale options are correct? It is difficult to guess whether your part has been correctly scaled or not after these options have been set.
You are now ready to proceed with processing the illustrator file.
Delete any text that SolidWorks may have generated (ie. "SolidWorks Educational Product. For instructional use only)
Select all of the lines and set the stroke width to 0.001in and color to pure red. (These steps are detailed further on in this guide)
You have now successfully prepared a SolidWorks part to be laser cut. Follow the rest of this guide for further instructions.
Flip the lever on the wall next to the laser cutter before operation (You should hear air start blowing)
Make sure there is not something hidden in the background that doesn't immediately show up on illustrator
Ensure that everything in illustrator is a vector
Lift the hood and check where the laser is pointing to confirm where exactly you are cutting
Check the extremes of the shape being cut on the material you are cutting
Try to avoid using warped materials
Jacobs Hall;
Three Universal VLS 6.60 (left) Located in 110c. and one Universal ILS 12.75 (right) Located in 120.
Invention Lab;
One VLS2.30 Located at the Citris Invention Lab.
Cory Student Workshop;
One PLS4.75 Located at the CSW.
In this course you will learn how to use the Universal Laser cutters to cut, score, and/or engrave a variety of materials. Laser cutting works by directing a high-power laser through optics onto a material which either cuts through or etches, depending on settings used. It is useful for precisely cutting 2D geometries and engraving images onto materials. Completion of this class will allow you to sign up for the Hands-On check out at Jacobs Hall. Once that step is completed, you will have access to the Universal lasers in Jacobs Hall, the Invention Lab, and the Cory Student Workshop.
Laser cutters are only operable while Design Specialists, or Student Supervisors with training are present.
Remember the buddy system- there must be a second person within earshot of you while working on the laser. Buddy system requirement will be a superuser requirement for CSW.
Any operation of the laser system is a potential fire hazard.
Most, if not all, materials are combustible in certain circumstances. Acrylic is especially flammable when vector cutting. Wood, paper, and plastics can all combust. NEVER OPERATE THE LASER SYSTEM WITHOUT CONSTANT SUPERVISION OF THE CUTTING AND ENGRAVING PROCESS. Exposure to the laser beam may cause ignition of combustible materials which can lead to a fire.
Any fire lasting more than half a second must be controlled. This list of steps begins with the simplest and escalates. Follow as many steps as necessary to extinguish any fire:
Lift the top door. This often stops small flames.
Turn off the exhaust system.
Blow on the material.
Remove the material if it is safe to grab a corner.
Spray water with spray bottle. Blue spray bottles are kept near each laser system.
If the fire is unmanageable, use the nearest fire alarm to contact the local fire department and evacuate the building.
Notify a technician immediately, even if a fire is small and easily extinguished. It’s important to know why it occurred, assess any damage, and prevent it from repeating. Discontinue using the laser until a technician has assessed that it is okay to resume.
Circumstances that can cause fire:
Files with lots of dense geometry very close together. This can cause the laser to repeatedly cut the same area, build up heat in one area and ignite it
Similarly, power settings too high for the material being cut and/or speed settings too slow
The laser is not focused properly (focus carriage is too close or too far from material). The laser is usually set up to focus automatically based on the thickness entered by the user but it can be disabled manually. Ask a Design Specialist to assist with this.
Attempting to cut materials on top of each other
Always remove all material including scrap material from the machine after use. Cordless vacuums are kept near the laser system. It is required to remove the cutting table and vacuum out the interior. Scrap material left in the laser system including materials that collect in the removable cutting table can be a fire hazard.
Exposure to the laser beam may cause physical burns and can cause severe eye damage. Proper use and care of this system are essential to safe operation.
Properly using the installed fume exhaust system is mandatory when operating the laser system. Fumes and smoke from the engraving process must be extracted from the laser system and filtered or exhausted outside.
Some materials, when engraved or cut with a laser, can produce toxic and corrosive fumes. If you are not sure of a material is laser-safe, you can consult with shop staff. We recommend that you obtain the material’s Safety Data Sheet (SDS) from the manufacturer of every material you intend to process in the laser system. The SDS discloses all of the hazards when handling or processing a particular material. Do not process any material that causes chemical deterioration of the laser system such as rust, metal etching or pitting, peeling paint, etc.
The Invention Lab lasers are on a first-come basis. Please be kind to your fellow users and be accommodating if you have a very long job.
Reservations can be made up to 7 days in advance.
Late & no-shows: After 10 minutes a reservation is forfeited and the remainder of the time is given to the first drop-in user. If you cannot make it to an appointment, please cancel it before it begins.
Unreserved times are designated drop-in use by anyone until the next reservation.
For the CSW, access requires the presence of superuser on first come first serve basis by checking shop calendar for superuser availability. Limiting access for maker-pass users for fairness to non-maker-pass users.
If a laser system breaks or is damaged while you are using it, inform the shop staff. Equipment damage is a normal part of the shop environment; for safety reasons it is important to inform a shop staff member immediately.
Always clean up fully after yourself. No material scraps should remain in the shop or in the machines.
If a laser system is not cutting material, the lens may need to be cleaned. Do not increase the intensity as this can cause the lens to burst. Notify a shop staff member and the lens can be cleaned if needed.
For your health safety and others in the shop, processing any material that is not laser-safe is against shop policy. Always check with a technician before assuming any material NOT purchased at the Jacobs Online store is okay.
PVC (aka Polyvinyl chloride, vinyl, pleather) is not laser safe. Chlorinated materials ( are corrosive to the machine and toxic
Chlorinated rubbers also release chlorine. Some paints contain chlorinated rubber.
Nitrile rubber releases hydrogen cyanide when combusted
Polystyrene foam (aka Styrofoam) - Melts and catches fire. Very dangerous.
Almost any foam - Including Foam core, polypropylene foam, etc. Very dangerous.
ABS off-gases hydrogen cyanide in fumes, a chemical known to be very toxic and has been used as a chemical warfare agent.
Polycarbonate (aka Lexan) - absorbs infrared radiation, causing it to melt and warp. Looks very similar to acrylic sheets.
Remember that all materials create fumes when laser cut. "Safe" materials are judged as such by not being overly combustible or releasing corrosive, mutagenic, or poisonous gases when laser cut.Always check with a technician before assuming any material NOT purchased at the Jacobs Online store is okay.
Paper / Cardstock - can be both etched and cut
Wood - can be both etched and cut
Cast Acrylic can be cut or rastered (has a frosted, translucent appearance)
Extruded Acrylic - can be cut (does not frost when etched)
Delrin - hard plastic, good for mechanical parts like gears (available in different hardnesses)
Cotton / Felt / Hemp - cuts well, engraves well
Polyester fabric - cuts okay, edges melt a bit, doesn’t engrave well
Leather - natural leather only, not synthetic “pleather”
Anodized Aluminum - can be etched (Black anodized aluminum provides best contrast out of all anodized aluminum)
Ceramic / Stone - Engraving is possible on porcelain, ceramic, terracotta slate, marble and stone
Brass - Uncoated brass can not be etched with a laser, it needs to have some kind of coating (such as paint).
Glass - Can be etched only. Must be flat. Etching colored glass has best visual results.
Rubber - Buna-N Rubber, Polyurethane rubber, natural rubber (no nitrile rubber or any chlorine-containing rubber)
Step 0 - File Setup
Files can be set up ahead of time to use time efficiently. Universal laser systems operate in one of two modes. A raster mode, in which images are marked or engraved into a material by etching a pattern of dots into the material at high resolutions up to 1000 dpi, and a vector mode in which the laser follows a two dimensional path to cut or mark a shape into a material. The printer driver determines whether an element in the graphic data being printed is a vector or raster object by its width.
The 3 laser cutters in 110C can cut 32" wide by 18" high, and the laser cutter in 120 can cut 48" wide by 24" high. The CSW laser cutter bed size is 18"x24". If you want to cut using the full cut area, set up the file you want to cut using 24", 32" or 48" for the width, and 18" or 24" for the height. Also select color mode RGB. This is crucial because the laser cutter software will not understand other modes.
Line thickness
Only lines and curves with a thickness of .001 in (.072 pt) or less will be interpreted as vector objects. All other elements of the graphic, including JPEG images, being printed will be interpreted as raster objects. In order to print vector elements, the software you are printing from must support creation of lines with a thickness of .001 in (.072 pt) or less. This includes Adobe Illustrator, Rhino, SolidWorks, AutoCAD, and other drafting software.
Line Color
Red lines indicate a line to be cut, Blue lines indicate a line to be scored, Black lines indicate a line to be engraved. When changing colors in Illustrator, use the following instructions to make sure you are using true RGB values;
1. To change line color, make sure your image is selected, then click on the color pallet icon in the tool bar;
2. Click on the "more" dropdown icon in the upper right of the colors box to choose "Show Options". Make sure RGB is also selected;
3. To make a cut or score line Make sure that the color choice is for "stroke" by clicking on the stroke square (which looks like a hollow red rectangle in the below icon). Now enter the correct values for the type of operation you want. For instance, To make a cut line enter 255 in the R setting, 0 in the G setting, and 0 in the B setting. To make a score line enter 0 in the R setting, 0 in the green setting, and 255 in the blue setting.
Step 1 - Clean off honeycomb cutting bed. Debris can be a fire hazard.
Step 2 - Load and Position Material
*When in the Invention Lab, open the ventilation gate located on the wall behind and to the right of the machine
Open the top door to the laser system and place material to be laser processed onto the engraving table. You may need to manually move the support table down to allow clearance to fit thicker materials into the machine. The material must be flat and consistent in thickness. The machine cannot remain focused on warped materials or materials that change in thickness/height.
*When at the CSW, turn the machine on in the correct order;
1.Press the power button on BOFA fume extractor
2. Turn the air compressor 90 degrees counterclockwise
3. Turn on the Laser Cutter
Step 3 - Sending to Universal Control Panel
Have you ensured that your illustrator file is the correct scale? If you do not know the scale, press Ctrl-R to bring up the rulers. See if your part is reasonably sized.
While still in Illustrator, click Print to open the printing options.
Click "set up" in the bottom, right corner
Open the preferences dialog. This will load the laser cutter's material settings database.
Laser Cutter Interface
Vector cutting depth and raster engraving depth (or marking intensity if you are surface marking only) are controlled by specifying the speed of processing and the laser power level for raster engraving and by specifying the speed of processing, laser power level and number of pulses per inch (PPI) for vector cutting and marking.
Materials are listed under various categories. Under the appropriate category or sub-category, select the material you are processing.
Enter the material thickness. Use calipers to measure the thickness accurately.
Click Defaults to reset the Intensity Adjustment sliders to 0%. Only adjust vector cutting intensity if needed.
Click OK, then click Print.
At the bottom right of the screen, click the Universal Control Panel icon.
Make sure the material is positioned correctly within the engraving area, and the geometry is positioned correctly in the Control Panel.
Close the top door.
Check that the fume exhaust is running and compressed air is flowing. Controls for each of these should be labeled near the laser.
Always ask a Design Specialist if you have any issues setting up your cut file or preparing the laser cutter.
Press the green START button on the UCP to begin laser processing.
The Universal software should be set to automatically focus based on the material thickness specified.
Order of execution when using the materials database tab proceeds with raster objects first, then vector marking objects and finally vector cutting objects.
It is not guaranteed that the laser will successfully cut through a material. It’s recommended to do a quick test cut:
Create a very small shape (such as a ½" - ¾” diameter circle) and position it in a marginal part of your material or another piece of the same material.
Cut the test geometry. As always, watch for anything
On the UCP, click “Settings” to re-open cut settings.
Adjust the intensity sliders on the top right but increase by small increments.
Then move the test cut shape in order to repeat.
Universal Laser Systems Safety and Operation Reference
Jacobs Hall;
Three Universal VLS 6.60 (left) Located in 110c. and one Universal ILS 12.75 (right) Located in 120.
Invention Lab;
One VLS2.30 Located at the Citris Invention Lab.
Cory Student Workshop;
One PLS4.75 Located at the CSW.
Course Synopsis
In this course you will learn how to use the Universal Laser cutters to cut, score, and/or engrave a variety of materials. Laser cutting works by directing a high-power laser through optics onto a material which either cuts through or etches, depending on settings used. It is useful for precisely cutting 2D geometries and engraving images onto materials. Completion of this class will allow you to sign up for the Hands-On check out at Jacobs Hall. Once that step is completed, you will have access to the Universal lasers in Jacobs Hall, the Invention Lab, and the Cory Student Workshop.
Laser Safety and Procedures
Laser cutters are only operable while Design Specialists, or Student Supervisors with training are present.
Remember the buddy system- there must be a second person within earshot of you while working on the laser. Buddy system requirement will be a superuser requirement for CSW.
Any operation of the laser system is a potential fire hazard.
Most, if not all, materials are combustible in certain circumstances. Acrylic is especially flammable when vector cutting. Wood, paper, and plastics can all combust. NEVER OPERATE THE LASER SYSTEM WITHOUT CONSTANT SUPERVISION OF THE CUTTING AND ENGRAVING PROCESS. Exposure to the laser beam may cause ignition of combustible materials which can lead to a fire.
Fire Protocol
Any fire lasting more than half a second must be controlled. This list of steps begins with the simplest and escalates. Follow as many steps as necessary to extinguish any fire:
Lift the top door. This often stops small flames.
Turn off the exhaust system.
Blow on the material.
Remove the material if it is safe to grab a corner.
Spray water with spray bottle. Blue spray bottles are kept near each laser system.
If the fire is unmanageable, use the nearest fire alarm to contact the local fire department and evacuate the building.
Notify a technician immediately, even if a fire is small and easily extinguished. It’s important to know why it occurred, assess any damage, and prevent it from repeating. Discontinue using the laser until a technician has assessed that it is okay to resume.
Circumstances that can cause fire:
Files with lots of dense geometry very close together. This can cause the laser to repeatedly cut the same area, build up heat in one area and ignite it
Similarly, power settings too high for the material being cut and/or speed settings too slow
The laser is not focused properly (focus carriage is too close or too far from material). The laser is usually set up to focus automatically based on the thickness entered by the user but it can be disabled manually. Ask a Design Specialist to assist with this.
Attempting to cut materials on top of each other
Always remove all material including scrap material from the machine after use. Cordless vacuums are kept near the laser system. It is required to remove the cutting table and vacuum out the interior. Scrap material left in the laser system including materials that collect in the removable cutting table can be a fire hazard.
Exposure to the laser beam may cause physical burns and can cause severe eye damage. Proper use and care of this system are essential to safe operation.
Properly using the installed fume exhaust system is mandatory when operating the laser system. Fumes and smoke from the engraving process must be extracted from the laser system and filtered or exhausted outside.
Some materials, when engraved or cut with a laser, can produce toxic and corrosive fumes. If you are not sure of a material is laser-safe, you can consult with shop staff. We recommend that you obtain the material’s Safety Data Sheet (SDS) from the manufacturer of every material you intend to process in the laser system. The SDS discloses all of the hazards when handling or processing a particular material. Do not process any material that causes chemical deterioration of the laser system such as rust, metal etching or pitting, peeling paint, etc.
Appointment Reservation System
The Invention Lab lasers are on a first-come basis. Please be kind to your fellow users and be accommodating if you have a very long job.
Reservations can be made up to 7 days in advance.
Late & no-shows: After 10 minutes a reservation is forfeited and the remainder of the time is given to the first drop-in user. If you cannot make it to an appointment, please cancel it before it begins.
Unreserved times are designated drop-in use by anyone until the next reservation.
For the CSW, access requires the presence of superuser on first come first serve basis by checking shop calendar for superuser availability. Limiting access for maker-pass users for fairness to non-maker-pass users.
Laser Work Space Etiquette
If a laser system breaks or is damaged while you are using it, inform the shop staff. Equipment damage is a normal part of the shop environment; for safety reasons it is important to inform a shop staff member immediately.
Always clean up fully after yourself. No material scraps should remain in the shop or in the machines.
If a laser system is not cutting material, the lens may need to be cleaned. Do not increase the intensity as this can cause the lens to burst. Notify a shop staff member and the lens can be cleaned if needed.
BANNED Materials
For your health safety and others in the shop, processing any material that is not laser-safe is against shop policy. Always check with a technician before assuming any material NOT purchased at the Jacobs Online store is okay.
PVC (aka Polyvinyl chloride, vinyl, pleather) is not laser safe. Chlorinated materials ( are corrosive to the machine and toxic
Chlorinated rubbers also release chlorine. Some paints contain chlorinated rubber.
Nitrile rubber releases hydrogen cyanide when combusted
Polystyrene foam (aka Styrofoam) - Melts and catches fire. Very dangerous.
Almost any foam - Including Foam core, polypropylene foam, etc. Very dangerous.
ABS off-gases hydrogen cyanide in fumes, a chemical known to be very toxic and has been used as a chemical warfare agent.
Polycarbonate (aka Lexan) - absorbs infrared radiation, causing it to melt and warp. Looks very similar to acrylic sheets.
Laser safe materials
Remember that all materials create fumes when laser cut. "Safe" materials are judged as such by not being overly combustible or releasing corrosive, mutagenic, or poisonous gases when laser cut.Always check with a technician before assuming any material NOT purchased at the Jacobs Online store is okay.
Paper / Cardstock - can be both etched and cut
Wood - can be both etched and cut
Cast Acrylic can be cut or rastered (has a frosted, translucent appearance)
Extruded Acrylic - can be cut (does not frost when etched)
Delrin - hard plastic, good for mechanical parts like gears (available in different hardnesses)
Cotton / Felt / Hemp - cuts well, engraves well
Polyester fabric - cuts okay, edges melt a bit, doesn’t engrave well
Leather - natural leather only, not synthetic “pleather”
Anodized Aluminum - can be etched (Black anodized aluminum provides best contrast out of all anodized aluminum)
Ceramic / Stone - Engraving is possible on porcelain, ceramic, terracotta slate, marble and stone
Brass - Uncoated brass can not be etched with a laser, it needs to have some kind of coating (such as paint).
Glass - Can be etched only. Must be flat. Etching colored glass has best visual results.
Rubber - Buna-N Rubber, Polyurethane rubber, natural rubber (no nitrile rubber or any chlorine-containing rubber)
Step 0 - File Setup
Files can be set up ahead of time to use time efficiently. Universal laser systems operate in one of two modes. A raster mode, in which images are marked or engraved into a material by etching a pattern of dots into the material at high resolutions up to 1000 dpi, and a vector mode in which the laser follows a two dimensional path to cut or mark a shape into a material. The printer driver determines whether an element in the graphic data being printed is a vector or raster object by its width.
The 3 laser cutters in 110C can cut 32" wide by 18" high, and the laser cutter in 120 can cut 48" wide by 24" high. The CSW laser cutter bed size is 18"x24". If you want to cut using the full cut area, set up the file you want to cut using 24", 32" or 48" for the width, and 18" or 24" for the height. Also select color mode RGB. This is crucial because the laser cutter software will not understand other modes.
File Requirements
Line thickness
Only lines and curves with a thickness of .001 in (.072 pt) or less will be interpreted as vector objects. All other elements of the graphic, including JPEG images, being printed will be interpreted as raster objects. In order to print vector elements, the software you are printing from must support creation of lines with a thickness of .001 in (.072 pt) or less. This includes Adobe Illustrator, Rhino, SolidWorks, AutoCAD, and other drafting software.
Line Color
Red lines indicate a line to be cut, Blue lines indicate a line to be scored, Black lines indicate a line to be engraved. When changing colors in Illustrator, use the following instructions to make sure you are using true RGB values;
1. To change line color, make sure your image is selected, then click on the color pallet icon in the tool bar;
2. Click on the "more" dropdown icon in the upper right of the colors box to choose "Show Options". Make sure RGB is also selected;
3. To make a cut or score line Make sure that the color choice is for "stroke" by clicking on the stroke square (which looks like a hollow red rectangle in the below icon). Now enter the correct values for the type of operation you want. For instance, To make a cut line enter 255 in the R setting, 0 in the G setting, and 0 in the B setting. To make a score line enter 0 in the R setting, 0 in the green setting, and 255 in the blue setting.
Laser System
Step 1 - Clean off honeycomb cutting bed. Debris can be a fire hazard.
Step 2 - Load and Position Material
*When in the Invention Lab, open the ventilation gate located on the wall behind and to the right of the machine
Open the top door to the laser system and place material to be laser processed onto the engraving table. You may need to manually move the support table down to allow clearance to fit thicker materials into the machine. The material must be flat and consistent in thickness. The machine cannot remain focused on warped materials or materials that change in thickness/height.
*When at the CSW, turn the machine on inthe correct order;
1.Press the power button on BOFA fume extractor
2. Turn the air compressor 90 degrees counterclockwise
3. Turn on the Laser Cutter
Step 3 - Sending to Universal Control Panel
While still in Illustrator, click Print to open the printing options.
Click "set up" in the bottom, right corner
Open the preferences dialog. This will load the laser cutter's material settings database.
Laser Cutter Interface
Vector cutting depth and raster engraving depth (or marking intensity if you are surface marking only) are controlled by specifying the speed of processing and the laser power level for raster engraving and by specifying the speed of processing, laser power level and number of pulses per inch (PPI) for vector cutting and marking.
Materials are listed under various categories. Under the appropriate category or sub-category, select the material you are processing.
Enter the material thickness. Use calipers to measure the thickness accurately.
Click Defaults to reset the Intensity Adjustment sliders to 0%. Only adjust vector cutting intensity if needed.
Click OK, then click Print.
At the bottom right of the screen, click the Universal Control Panel icon.
Before Starting The Laser Cutter
Make sure the material is positioned correctly within the engraving area, and the geometry is positioned correctly in the Control Panel.
Close the top door.
Check that the fume exhaust is running and compressed air is flowing. Controls for each of these should be labeled near the laser.
Always ask a Design Specialist if you have any issues setting up your cut file or preparing the laser cutter.
Press the green START button on the UCP to begin laser processing.
The Universal software should be set to automatically focus based on the material thickness specified.
Order of execution when using the materials database tab proceeds with raster objects first, then vector marking objects and finally vector cutting objects.
Test Cuts First
It is not guaranteed that the laser will successfully cut through a material. It’s recommended to do a quick test cut:
Create a very small shape (such as a ½" - ¾” diameter circle) and position it in a marginal part of your material or another piece of the same material.
Cut the test geometry. As always, watch for anything
On the UCP, click “Settings” to re-open cut settings.
Adjust the intensity sliders on the top right but increase by small increments.
Then move the test cut shape in order to repeat.
Costs at least at Jacobs; parts are free
Glass transition at a slightly higher temperature (~ higher)
When it comes to sizing holes, make sure that there is actually a drill bit or end mill with the correct diameter for your hole. Perform a google search for a drill bit sizing chart or see the table here: for a conversion between letter and number drill bits to decimal inches.
That being said, there are some parts that are great candidates for CNC and it can certainly be a useful technology. Small parts especially will be easier to make (see: ) and can make design significantly easier.
As a general rule, simple geometry is better. Things like right angles and low requirements for accuracy and precision (see: ) make everyone's lives easier.
For the Jacobs Hall lasers, the reservation system can be found at . Please prepare your cut file in advance and estimate the cutting time using the Universal Laser software. See the Laser Cutter Interface section below regarding estimating cutting time.
Construction grade plywood - Most plywood sold in hardware stores is not bonded with modified adhesives making it prone to smoking, flaming, charring at the edges and producing toxic fumes (: No Knots, Thicker/Less Ply, Interior Grade, urea-formaldehyde(UF) or melamine-formaldehyde(off-gasses less formaldehyde) )
.
*
These parameters are specified in the laser cutter preferences interface by one of two methods. The two methods are laid out in tabs in the laser cutter interface. The first method is a materials database method which simplifies setup for beginners and casual users, the second method is a manual method with allows much more control for advanced users. Each method treats assignment of laser job settings to colors in the graphic being printed and interpretation of raster and vector elements in the graphic being printed in slightly different ways.
It will load the geometry into this screen.
For the Jacobs Hall lasers, the reservation system can be found at . Please prepare your cut file in advance and estimate the cutting time using the Universal Laser software. See the Laser Cutter Interface section below regarding estimating cutting time.
Construction grade plywood - Most plywood sold in hardware stores is not bonded with modified adhesives making it prone to smoking, flaming, charring at the edges and producing toxic fumes (: No Knots, Thicker/Less Ply, Interior Grade, urea-formaldehyde(UF) or melamine-formaldehyde(off-gasses less formaldehyde) )
.
*
These parameters are specified in the laser cutter preferences interface by one of two methods. The two methods are laid out in tabs in the laser cutter interface. The first method is a materials database method which simplifies setup for beginners and casual users, the second method is a manual method with allows much more control for advanced users. Each method treats assignment of laser job settings to colors in the graphic being printed and interpretation of raster and vector elements in the graphic being printed in slightly different ways.
It will load the geometry into this screen.
Basic View (default mode) • The Basic View shows a preview window of the job currently selected. • The cursor becomes a magnifying glass (Zoom Tool) if you pass it over the preview window. Left-clicking the mouse zooms in and right-clicking zooms out. (Mouse scroll wheel can be used in any mode to zoom in and out.) • Selecting the Settings button takes you back to the printer driver interface to allow you to change most of the settings for the job selected. Keep in mind that some settings cannot be changed after printing from your graphics program, such as print density and vector quality. If a setting is not adjustable after printing from your graphics program, it will be grayed out or not appear at all when you press the settings button in the UCP. |
The Focus View feature allows you to quickly manually move the focus carriage to a desired position in the material processing field. This is useful for focusing, as well as testing whether the geometry falls within the material. |
The Relocate feature gives you the ability to move the image in the selected job to another area of the engraving field. This feature does not permanently modify the original image location. |
The Duplicate feature gives you the ability duplicate an image in a grid pattern. You can select how many rows and columns of the image as well as the spacing between the rows and columns. |
The estimate feature approximately calculates the amount of time it will take the laser system to process the selected job. For more complex jobs, the estimate feature can take a while to estimate the job completion time. A job can be estimated while a machine is disconnected or turned off. |
Basic View (default mode) • The Basic View shows a preview window of the job currently selected. • The cursor becomes a magnifying glass (Zoom Tool) if you pass it over the preview window. Left-clicking the mouse zooms in and right-clicking zooms out. (Mouse scroll wheel can be used in any mode to zoom in and out.) • Selecting the Settings button takes you back to the printer driver interface to allow you to change most of the settings for the job selected. Keep in mind that some settings cannot be changed after printing from your graphics program, such as print density and vector quality. If a setting is not adjustable after printing from your graphics program, it will be grayed out or not appear at all when you press the settings button in the UCP. |
The Focus View feature allows you to quickly manually move the focus carriage to a desired position in the material processing field. This is useful for focusing, as well as testing whether the geometry falls within the material. |
The Relocate feature gives you the ability to move the image in the selected job to another area of the engraving field. This feature does not permanently modify the original image location. |
The Duplicate feature gives you the ability duplicate an image in a grid pattern. You can select how many rows and columns of the image as well as the spacing between the rows and columns. |
The estimate feature approximately calculates the amount of time it will take the laser system to process the selected job. For more complex jobs, the estimate feature can take a while to estimate the job completion time. A job can be estimated while a machine is disconnected or turned off. |
Here are some general tolerancing tips, picked up from work experience, in no particular order. Anyone is welcome to add to these or correct them if you see something inaccurate.
Tolerances should always be as large as possible for the part to still function
Overly tight tolerances are expensive, time consuming, and unnecessary
3D printed parts will shrink. A lot.
Online estimates are ~8% for ABS and ~3% for PLA but the actual amount will vary drastically based on the printer, settings, and the part itself.
If possible, part corners should be chamfered or filleted, especially for sharp/hard materials
For machined parts, a surface finish of 125 microinches (3.175 micrometers) is standard
Any holes to be tapped should be first made one size smaller than the tap size
I.e. for a #6 screw, one should drill a #5 hole before tapping with a #6 tap
Holes should be larger than the fasteners that go in them. The smallest diameters for a "normal" fit by ASME standards are listed below.
See ASME standard 18.2.8 for more information, or go to: https://mechanicalc.com/reference/fastener-size-tables
GD&T should be added at some point
Shoutout to Dennis K. Lieu
Coarse threads are the most commonly available and should be suitable for almost all use cases
Before choosing to use metric threads, please coordinate with you project team to ensure the type of thread used is consistent.
When working on a project or part, try to minimize the number of different sizes of screws used. Avoid having a variety of screw sizes.
Try to keep screw drive type consistent.
Use the clearance hole chart in the "Tolerancing" page for appropriate clearence hole sizes.
Be mindful of the size of the screw head when designing a part, especially of how the head affects clearance to other parts. It can be useful to obtain the SolidWorks model of a specific screw (commonly avaliable on McMaster) to check for clearance issues.
Screws used as a hinge, such as part of a screw-nut hinge combination, and other structural-critical screws should have an appropriate thread locker (such as Loctite 242) applied.
Screws and standoffs used in close proximity to exposed electronics should ideally be non-conductive.
Always make sure the nut you get corresponds with the thread of the screw that you are planning on using it with.
The most common type of nut that we use is a hex nut.
Nylock nuts are the common alternative if a more secure connection needs to be made.
In nearly every case, nuts require much more clearance than screws and thus are usually oriented away from moving parts and where they can't come into contact with other surfaces.
Threaded inserts can be extremely useful way of having a threaded connection in your designs.
A very common situation that can arise is a need to thread into 3D printed parts. 3D-printed parts are difficult to tap (use a tool to create threads on the inside of a hole) because plastics (especially for PLA) deform at low temperatures. 3D-printing internal threads are also difficult because of the need for high precision. Directly threading a screw into a part is often not ideal, because repeatedly removing and screwing the fastener will appreciably lower the integrity and strength of the connection.
As such, threaded inserts are an ideal solution to this issue, since the insert is designed to be permanently secured to the part yet also allow for the repeated insertion of a screw into the thread. An analogous way of achieving this is to design the part to hold a captive hex or square nut inside. In this case, the nut acts as the insert. More information about plastic-specific inserts can be found here:
Another common situation is a need for a thread into a soft metal, such as aluminum. Aluminum is often desirable, especially for aerospace applications, because of its low weight. However, it is not ideal to directly thread into aluminum for the following reasons:
Most fasteners are steel, which is considerably stronger than aluminum. A threaded interface between steel and aluminum can cause significant wear to the internal threads of the aluminum leading to issues such including binding.
For a reference on dimensions on mil-spec threaded inserts, see the below documents:
Rivets are permanently-deforming fasteners. Please do not use rivets unless you have a very good reason to do so, as they prevent the disassembly of the part (without an angle grinder). There is little information on rivets included here on purpose. Rivnuts or Nutserts are slightly better, but also have issues related to their deformation.
When you have money but you'd rather have raw material, fasteners, and other fun things
Jacobs sells at-cost and is often the best option available. Most commonly, plywood for laser cutting and 1/8" and 1/4" 6061 aluminum sheets are cheaper here than anywhere else.
Would you like some Delrin? Lexan? ePlastics is pretty cheap and easy to order from on-line. Would recommend.
If you need any 8020 extrusions or parts, this is the place to go. They give a 10% discount, but they sadly don't do sponsorships. They can also give
some design advice and they can answer more specific questions about 8020 that can't be answered on the website (you can also search the catalog)! Michael and Benson have been in contact with David Morton from there. His email is david.morton@tecotechnology.com
Good customer service, highly recommend.
Screws, bolts, washers, nuts, threaded rods, tooling, some stock, and similar are the most common purchases from McMaster. Many other parts (gears, linear bearings, pumps, etc.) are available but may be prohibitively expensive.
If you need pipe fittings, valves, regulators, or really anything for propulsion, Swagelok is our go-to supplier.
Buy components from Digikey. Really everything should come from here.
If you can't find it on Digikey, maybe you can find it here?
Apparently Arrow is actually the largest supplier of these three by volume, so you should probably be able to find it here if not at the other two.
80/20 Inc. has a fantastic website detailing a lot of information about their extrusions.
This page is intended to serve as a summary and introduction to these extrusions.
The most useful part of this page is probably the Tips and Tricks section at the bottom.
8020 is a brand of Aluminum extrusions. "Extrusions" just means that they are parts with a constant cross section that are extruded through a dye in their manufacturing process. 8020 sells an entire product ecosystem that revolves around their "T-slot" extrusions. Their cross section looks like this:
8020 parts are often used to build frames and other equipment quickly and more conveniently than alternatives (such as welding, manufacturing custom parts, etc.). They are widely used in industry for several reasons:
They are easy and convenient to use
While they can be pricey, they are high quality and are usually cheaper than a custom solution
They are very versatile and can be used for many types of applications
They can be expanded to include linear motion bearings, stanchions, guard railings, fences, etc.
The basic principle behind fastening 8020 extrusions is called the "2 degree drop lock"
The main idea here is that the edges of the extrusions are not perfectly parallel to each other, but rather offset by 2 degrees (this can be a pain in SW sometimes, be aware). When a fastener is tightened, it elastically deforms the extrusion, creating a strong normal force on the nut and fastener head. This normal force allows for a large static friction force to be applied, securing the nut in place.
For reference, on of these fasteners can usually hold up to several hundred pounds when installed properly.
8020 has a lot of options, which is fantastic. However, this can be intimidating for first-time users. This guide is intended to help you through selecting 8020 components for your assembly
For most applications at STAR, we do not use metric extrusions or fasteners. This leaves you with two choices for the extrusion series:
1010 - This is a 1" x 1" extrusion. This will usually be enough for most applications where the structure is not under significant or mission critical load.
1515 - This is a 1.5" x 1.5" extrusion. This is the maximum imperial sized extrusion, and is used for more "beefy" structures.
Extrusions are also available in non-square shapes. For example, a 1530 extrusion will measure 1.5" by 3", indicating that it is essentially two 1515 extrusions connected side by side. These are still compatible with other extrusions in their series
Note that for each of these extrusions, there are submodels such as "1515-S-Black-FB". These indicate unique features of the extrusion. Be mindful of these, since they can at times compromise strength or offer options for weight reduction. There are countless options, but these are a few to be aware of:
S indicates a smooth finish
Lite indicates a lighter but weaker profile. Lite gets abbreviated to L if there are other modifiers (about 22% lighter than regular
UL stands for ultra light (about 12% lighter than L, 32% lighter than regular)
Black indicates a black anodized finish. More expensive, questionably more corrosion resistant.
Fasteners are an integral part of 8020 product selection. The 8020 catalog provides a good amount of detail on the differences between fasteners, and their youtube channel is also recommended for seeing how these work in action.
There are several questions to keep in mind when selecting a fastener:
How strong will the fasteners be?
How much machining will be necessary on the profiles?
We can order parts pre-machined, but it does cost more money. Machining parts ourselves is also possible, but is very time-intensive.
How often will this fastener need to be removed? Will it need to be removed after the assembly is assembled?
What are the loads going to be on the fasteners?
A force applied perpendicular to the T-slot and the axis of the screw will differ greatly from a force applied along the T-slot, which will both be very different from a torque in the axis of the screw.
For small orders, 8020.net is fine. For larger orders, please email David at TECO technologies.
Don't make the same mistakes we did.
PLEASE PLEASE PLEASE if your budget permits order parts pre-cut and pre-machined. It saves a lot of headache on our side, and the whole point of 8020 is that it's easy.
If your budget does not permit, reconsider your budget. Machining and cutting 8020 for an average-sized project will take well over 10 hours in the machine shop for the average student.
If you've reconsidered your budget and still can't afford, buy extra length of 8020, since cutting and mistakes will eat up your length. Also order extra fasteners
Try to stick with flat plates and gussets. Anchor fasteners are difficult to access and expensive, and end fasteners require tapping into the aluminum, which isn't ideal for things that need to be disassembled frequently. 45 degree supports are also very nice for high-strength applications.
When tightening fasteners, you almost can't go too tight. Most people will not tighten the fasteners enough to engage the 2-degree drop lock on the first try.
Think about accessing fasteners when you create your assembly. A fastener is no good if you can't get in with a hex wrench to tighten it.
Be mindful about constraining these, since the 2-degree drop lock means that seemingly parallel planes are not actually parallel
8020 becomes very useful when you interface it with your custom parts. This is not very difficult to do, and essentially just involves including an equivalent flat plate fastener in your part.
For a more in-depth treatment, refer to this fastener handout:
If working in US customary units, refer also to the Wikipedia page on the Unified Thread Standard: If working in SI units, refer to the ISO thread sizing Wikipedia page:
can always be of concern when joining two dissimilar metals.
Again, threaded fasteners or captive nuts are ideal in this scenario. When choosing inserts for aluminum, make sure they are passivated or mil-spec, as to prevent galvanic corrosion from occurring. can be ideal for this application.
Check out the page if you're not sure what you want.
When creating 8020 assemblies in SolidWorks, use the models provided on 3D Content Central ()
Designation
Nom. (in)
Nom. (mm)
Min. (in)
Min. (mm)
#0
0.060
1.524
0.076
1.930
M1.6
0.063
1.600
0.071
1.800
#1
0.073
1.854
0.089
2.261
M2.0
0.079
2.000
0.094
2.400
#2
0.086
2.184
0.102
2.591
M2.5
0.098
2.500
0.114
2.900
#3
0.099
2.515
0.116
2.946
#4
0.112
2.845
0.128
3.251
M3.0
0.118
3.000
0.134
3.400
#5
0.125
3.175
0.156
3.962
#6
0.138
3.505
0.170
4.318
M4.0
0.157
4.000
0.177
4.500
#8
0.164
4.166
0.196
4.978
#10
0.190
4.826
0.221
5.613
M5.0
0.197
5.000
0.217
5.500
#12
0.216
5.486
N/A
N/A
M6.0
0.236
6.000
0.260
6.600
1/4"
0.250
6.350
0.281
7.137
M8.0
0.315
8.000
0.354
9.000
A description of each of the main components which make up the airframe of a rocket.
Tubing is probably the essential airframe component as it makes up almost all of the exterior structure and shape of the rocket. Historically, we have mainly used BlueTube as our default tubing material, but we are moving towards carbon fiber for our larger rocket designs as it offers a great combination of strength and low weight.
The Payload Tube is the tube dedicated to housing the payload, whatever it may be. This is generally directly under the nose cone as the payload is often partially stored in the nose cone as well to efficiently utilize all available space.
The Avionics Bay (or Av Bay) houses all of the electrical boards, flight computers, and avionics of the rocket. As this is a very delicate section of the rocket, it is generally closed/sealed on both ends by bulkheads. It also usually has a door, sled, or other form of access so the Avionics team can access the boards at anytime time, even when the rocket is on the launch rail.
The Recovery Tube houses the parachutes (and supporting recovery components) of the rocket. This section of the rocket has to be able to separate to allow the parachutes to release after apogee has been reached. In the past this separation has been done via black powder.
The Booster Tube is at the bottom of the rocket and houses the motor. It is generally sealed off from the rest of the rocket.
Couplers are tubes that work as connecting sections of the rocket that have a slightly smaller diameter than the rocket itself, so that they can fit snugly inside of it and allow different rocket tube sections to mate. They are permanently attached to these tube sections and generally made out of the same material as the main tubing.
Bulkheads are the "dividing walls" of the rocket or in other words structural sealing tools that are fitted inside the tube and comprise the entire area of the inner tube. They are used to seal off sections of the rocket where we do not want any interaction, such as between the motor and whatever is above it. They are also used as structural mounting spots for things like parachute u-bolts. Sometimes they have holes so that pipes can pass through them. Historically, we have made these out of wood. We are planning to use acrylic for our larger rockets.
Centering rings are structural tools used to hold things in place inside of the rocket. They are similar to bulkheads except that they have a hollow center (ring instead of circle). We have used them to secure the payload in the nose cone and secure the motor tube inside of the booster tube. When used to center the motor, they should be strong enough to withstand high impulses that the motor produces during flight. Historically, we have made these out of wood. We are planning to use aluminum for our larger rockets.
The cone shaped nose of the rocket that is designed to reduce drag at the front end/top of the rocket. We generally go for nose cones that are made of carbon fiber and have a 4:1 length to diameter ratio (a 6in diameter rocket would have a 24 in length nose cone).
A custom piece of tubing that is made to facilitate a diameter transition in a rocket. For example, a transition piece was used in Arktos to transition from a 6in diameter (nose cone and payload tube) to a 4in diameter (recovery, booster, av bay). Transition pieces allow for versatility by allowing certain parts of the rocket to house larger diameters without requiring the entire rocket to commit to the larger size.
A stabilizing agent that is fitted to the bottom of the rocket.
Similar to the nose cone, but at the very end of the rocket. A tail cone exists to buffer the change at the bottom of the rocket from "whatever diameter" to nothing (i.e. where the rocket ends). Adding in a piece that gives a gradual change in diameter helps to eliminate drag and achieve a higher apogee.
How to put together some tubes
Rocketeers traditionally use friction fits for low-power, mid-power, and most L1 and some L2-level rockets. Take this example of a rocket with a single-deploy, motor ejection recovery system:
There are three interfaces marked with vertical lines; the green one is the only interface required to be separable, as it is where parachutes exit the vehicle. In this case, we rely on the friction between the electronics bay coupler (fore) and the booster tube (aft) to keep the upper and lower section from moving relative to each other on ascent after the motor has burned out.
If a friction-fit interface is not tight enough, drag separation can occur. While separation during powered ascent is less likely, after the motor has stopped producing thrust, it is possible that the drag force experienced by the lower section of the rocket (including fins) is greater than that experienced by the upper section. When this imbalance of forces occurs, it is possible for the lower section to accelerate relative to the upper section. This is known as drag separation, and is not always a bad thing; it can even be desirable if used for stage separation.
It can be more of an art than a science to get a good friction fit. Generally, we recommend following this (paraphrased) advice from Dave Raimondi (ex-LUNAR President, L3-certified):
Your friction fit should allow you to gently lift the rocket in the air by the upper section and hold it such that it is stable and not touching the ground. Then shake the rocket and make sure the bottom section separates with some effort, but does not require violent shaking.
To adjust your friction fit, either: remove/add masking tape to the coupler, or, if no masking tape remains and it is still too tight, sand down the coupler/inside of body tube. We recommend adding tape one layer at a time, either in entire rings or even half rings for fine-tuning. Use wide painters or masking tape for best results (> 1" wide). There is a fair amount of tolerance on the above advice; don't be too worried if your fit seems to be a little too loose or a little too tight.
Any rocket with dual-side dual-deploy recovery will require a stronger interface to keep the main parachute from coming out. Also consider using a stronger interface for larger and heavier rockets, as they may be subject to larger forces. Refer also to the many forum threads like these for more information:
Shear pins are fasteners designed to hold an interface together, but break (shear) when recovery energetics (black powder, usually) are activated. They may also be used to retain deployable payloads. The driving mechanism for shear pin failure is the transverse loads applied by each section of tubing (coupler, body tube) as pressure is built up inside the airframe; the shear pins are not vaporized, melted, or otherwise affected by recovery charges.
STAR members have traditionally used #2-56 or #4-40 nylon screws (e.g., from McMaster-Carr) as "shear pins". While these screws technically have threads, they are often more of a press-fit than screwed into the airframe. No female threads (nut/threaded insert) are required. Shear pins have been effectively used with BlueTube and fiberglass airframes.
Using too many or too few shear pins can result in extreme quantities of black powder being required, or the premature separation of the airframe in flight, respectively. STAR has experience with both of these scenarios. Only testing can truly help you avoid these outcomes. Short of testing, precise calculation of the loads may be helpful; however, it is generally quite difficult to estimate exactly what loads will be applied to each shear pin.
Note that dynamic loading when the main parachute opens is usually far higher than any other load during flight; if shear pins are used to retain a payload through/after main parachute deployment, pay special attention to this interface to ensure it does not break prematurely.
When it comes to larger or more complex rockets, it is expected that you will have one or more interfaces that you need to be separable during assembly, but do not come apart during flight. These are generally held together with some sort of fastener. One common example of this type of interface is a nosecone that detaches from the payload tube to allow for the insertion of a payload, but does not need to detach during flight.
It is certainly possible to epoxy an ordinary hex nut (see: Fasteners) to the inside of a coupler and thread into it with a machine screw. That being said, we recommend using one of the below options for better reliability and/or convenience. Trying to properly position a normal or low-profile hex nut can be difficult and can result in getting epoxy in the threads or a poor bond with the airframe.
Nut plates and weld nuts essentially refer to the same thing: a normal nut, but attached to a wide base that permanently attaches to a surface. Once the weld nut is attached to a surface, it offers female threads for a removable but secure attachment (similar to a threaded insert). Traditionally in aerospace (especially planes!), nut plates are attached to a surface with rivets while weld nuts (more common in cars) are literally welded to a surface. "Adhesive-mount nuts" are also sold with the explicit purpose of being attached with an adhesive, although most weld nuts/ nut plates are fine to use with epoxy.
To use a weld nut or nut plate with epoxy for a coupler-body tube interface, follow these rough steps (also see below for references with pictures):
Test fit coupler and body tube together and tape/ hold interface so tubes do not rotate relative to each other
Drill a hole (free fit tolerance for the screw that will be used) radially through both body tube and coupler
Insert a screw radially inward through the hole, going through both the body tube and coupler.
Hold the nut on the inside of the coupler and thread it onto the screw
Mark out area for epoxy around footprint of nut
Remove nut and apply epoxy, taking care to avoid the hole where the screw will go. Remember that when the epoxy is compressed, it will spread out, but should not enter the screw/nut interface.
Thread nut back on to screw, stopping right before it touches the epoxy
Pull screw radially outward, pressing nut into epoxy
Hold nut static (use pliers if needed, clean afterward with isopropyl alcohol) while screwing in screw completely to apply medium pressure
As epoxy cures, make sure that the screw is still removable. It is very possible to accidentally permanently epoxy the screw to the nut, rendering the connection useless. We recommend keeping pressure at least until the epoxy has set, periodically removing the screw to check that the threads are still useable
See this fantastic tutorial on how to use weld nuts/nut plates with fiberglass airframes: http://hararocketry.org/hara/how-to-use-weld-nut-plates-on-fiberglass-rocket/ A similar write-up can be found in Apogee Newsletter 341: https://www.apogeerockets.com/education/downloads/Newsletter341.pdf
Historically, STAR has used #4-40 pan head sheet metal screws (from ACE Hardware or McMaster-Carr) to semi-permanently attach Blue Tube interfaces. Sheet metal screws are similar to wood screws in that they have deep, aggressive threads and a sharp point; however, unlike wood screws, they are threaded all the way until the head. This property makes them useful even at very short lengths (1/2" or 1/4" long).
As a sheet metal screw directly cuts into the airframe, the material that said sheet metal screw is holding onto is gradually removed each time the screw is inserted and removed. Practically, this manifests itself as the screw feeling loose and/or simply falling out after too many uses. The screw may also bind in the interface at an angle, instead of remaining perpendicular to the long axis of the rocket.
While Blue Tube generally accepts ~10 or more assembly/removal cycles without any issues and up to 20-25 without serious concern, you may start to notice sheet metal screws in fiberglass becoming loose after as few as 4 cycles (typ. 6-8). This is in part due to the fact that Blue Tube, as a paper composite, will recover its shape more easily after being deformed. While it is possible to attempt to remedy a too-large hole with some epoxy, it is often easier to simply drill another hole and fill the previous one entirely. Depending on the epoxy used, this may take up to 24 hours to completely cure. For a project team on tight assembly timelines and an interest in professionalism and reliability, we do not recommend sheet metal screws for composite airframes. Do not underestimate the potential timeline and build quality impact a poor tube connection can cause.
Self clinching nuts, sometimes called PEM nuts or press fit nuts, are nuts designed for installing a permeant fixture of female threads in a hole of sheet metal.
After a hole is drilled with the right diameter, the nut can be press fit into the hole. This process will deform the metal to envelope the back tapered shank and hold the nut in place, as well as imbed serration to provide torque resistance.
Rockets are usually not made of sheet metal, but these nut have been seen to work on fiberglass tubes. Do note that for tubes under 2.5" in diameter, the curvature of the tube may be too great for the nut to properly work, as they are design for flat surfaces. It is also important to buy nuts that are suited for the thickness of the tube wall. Additionally, ensure you have the right size drill bit, as hole diameter is crucial to ensure the nut press fits well.
Specialized tools can be used to press fit the nuts into place, but simpler methods can also be effective. By using a screw or bolt that is compatible with the nut, one can tighten the screw and effectively "press" the nut into the drilled hole. A washer can be used to create a better clamping surface, but may not be necessary.
Some people choose to also add epoxy to the nut to increase the strength of the nut to the tube. It likely depends on serval factors for how well the nut actually stay in place, but in flight when the nuts are engaged with the screws, they shouldn't go anywhere. The screw shearing off is more likely than the nut failing all together. Multiple nuts should be used to make a good permanent connection between to pieces of the rocket. It is also recommended that the screw sizes should be slightly longer than they need to be, so in the case of the screws shearing off, they can still be removed from the nuts. Even then, it is recommended to not use these nut for shear pins/screws, and to go with the more traditional technique outlined above.
CalSTAR Composites Best Practices
This technical note condenses practical knowledge about producing composite parts from the CalSTAR team and alumni. Focus is on materials and best practices: what to use, where to get it, and how to use it. This document is not a replacement for hands-on practice and self-driven learning, but it should give newer team members a good head start.
Unlike a typical engineering note, this document is a living article with no restricted author list and no formal revision structure. Therefore, when editing, please be concise, neutral, and specific. This document is a forum for imparting hard-won composites knowledge, rather than hard-won personal philosophy. With the exception of diatribes against Bondo. These are fair game.
Use good safety practices (gloves, goggles, avoid skin contact, ingestion, inhalation, etc) with all resins and materials described below. Read the MSDS and be aware of safe disposal methods as well as safe use. This document makes no attempt at a complete description of safe handling or risks of the materials described. Some particular examples of the safety precautions to be aware of are:
Again, it is essential to properly research for yourself the risks and best safety practices for each material and process before use. If you are unsure, it is always better to contact a lead and ask for assistance than to endanger yourself.
Resins are usually used with a reinforcing fiber or filler. Common resins fall into the categories of epoxies, polyesters, vinyl esters, and cyanate esters. Most layups generally use:
Cyanate esters behave similarly to epoxies, and are the most common resin system for prepreg.
Understand that all vinyl esters and polyesters require fitted working respirators, to avoid breathing in the solvents, this should be done with zero ex
Also understand that vinyl esters and polyesters should only be used in conditions with good ventilation and no spark / fire hazard, as the aerosols are flammable.
Many dusts and fillers are bad to breathe -- when in doubt wear a dust mask.
If material like a resin gets on the skin, it is usually incorrect to attempt to “wash” it off with a solvent. The reasoning is that the solvent will simply dissolve the material and make it easier to penetrate the skin! Use soap and water with manual scrubbing instead.
epoxy as the matrix for fiber-reinforced laminates
vinyl ester as the matrix for fiberglass molds
polyester (e.g. gel coat) as the hard surface coat for molds – if molds are used.
These resins are all thermosets. In other words, the curing process is a 3D chemical cross-linking, where the mers (short CH molecules of which the resin is composed) grow strong links to one another. The process is both heat-driven and exothermic, so it accelerates itself. This means two things:
You can speed up a cure by heating the resin.
Thinly spread resin (volume / surface area = low) will cure much more slowly than a mass of resin in a container (volume / surface area = high).
With regard to point (2), a large mass of curing resin left in a cup will often turn brown, smoke, and put off foul smells and lots of heat. (The self-accelerating effect is compounded by the fact that polymers have low thermal conductivities, so the heat cannot escape the curing resin easily.) Therefore always dispose of excess resin by spreading it over a large area of paper or plastic, and letting it cure in that spread-out state.
The 105 epoxy system is the default for laminated parts. Various hardeners can be combined with 105 resin to adjust cure time and cured part properties. Usually the 209 hardener is chosen, which gives a long pot life, so that the layup will not be rushed. The 105 system features a low viscosity, making it a good laminating resin. The main downside of the 105 system is its low Tg (~120°F).
9396 is one of the stiffest and most temperature-resilient (service temperature up to 350°F) structural epoxies. It is more difficult to use in laminations due to having a higher viscosity and shorter pot life than West System 105/209. (However, the team has made many successful laminations with 9396.) It can be used as a good adhesive, and is the best option for laminates or bonds in close proximity to intense heat sources (like the exhaust). 9396 is effective as a potting and repair resin. Expect working life on the order of 1.5 hours, and at room temperature, 70% cure in 24 hours, with full cure in several days. At elevated temperature (~135°F), cure time can be significantly reduced to ~1.5 hours.
Tap’s 4:1 epoxy is moderately stiff and strong. It has the benefit of being readily purchased on short notice, and can be used for general purpose potting and lamination. However, as a general purpose resin it makes significant compromises: it has a higher viscosity than 105 and a shorter pot life than both 105 and 9396. Expect a working life of less than 15 minutes.
The team has usually used Tap’s polyester resin, and found it serviceable. Polyester alone can be used as a matrix for fiberglass molds, and finds few other applications. In fact, other Berkeley teams have frequently used vinyl ester instead of polyester for fiberglass molds, since the vinyl ester is more thermally stable and bonds better to epoxy than polyester.
A polyester product called “gel coat” comes pre-filled with talc, CaCO₃, and other mineral oxides so that it can produce a thin, hard surface layer in molds. Tap’s gel coat has most frequently been used by the team for fiberglass molds. For surfacing of urethane foam plugs, a similar product called Duratec is probably superior in hardness and in holding a smooth surface during sanding; in a pinch gel coat on urethane may suffice.
Vinyl ester is very similar to polyester in processing behavior. It is somewhat more expensive than polyester, but deforms less under temperature and bonds well to both polyester and epoxy. Vinyl ester is the usual choice of matrix for fiberglass molds – this because fiberglass can be more demanding of a perfect medium for a usable quality layup. Tap’s vinyl ester product has generally been used.
Cyanate ester is the most common resin system for prepregs (frozen fiber tapes pre-impregnated with resin). Once cured, it is mechanically similar to epoxy, but has better resistance to hot-wet conditions. In the uncured state it is very sensitive to moisture. When removing prepreg from the freezer, where it should be stored prior, it must be allowed to come to room temperature before opening the bag. Otherwise condensation on the material will ruin it. When repacking prepreg for putting back into the freezer, include a dessicant pack and seal the bag well. Cyanate ester systems require heat to properly cure. Most of the prepreg we will likely use is RS3, and cures when held at 350°F for several hours. There are published schedules of heat and pressure to define good cure cycles for various resin systems.
For the most part, the team has used high-strength carbon fibers such as AS4 and IM7. These have relatively low modulus and fall into the “black aluminum” design regime. A key decision when acquiring fiber is the form of the fabric: whether to get unidirectional or woven, and if woven, what type of weave. It has been useful to get a moderate amount of unidirectional material for making strength-controlled shear panels, but for the majority of parts that are not filament wound, we will use woven cloth.
Satin or twill weaves are much easier to control during layup than plain weave. Plain weave is very difficult to use in any part with bi-directional curvature or uni-directional curvature tighter than ~200 mm radius. Therefore it is advisable to always insist on 5 harness satin or twill. Fiber areal weight of ~6 oz/yd² is generally useful. In special applications, lighter fabrics may be desirable.
Carbon fiber composites have good electrical conductivity in the plane of the laminate, but if using the carbon for example as a grounding body, it is necessary to drill into it and install a metal stud which will bypass the current past the surface epoxy (which is non-conductive) and into the center of the laminate, where contact can be made with the exposed carbon fibers. Carbon fabrics are easily cut with good, sharp shears.
By experimentation, we have found that plain weave final product should be around 0.35-0.36 g per square inch.
The usual glass in fiberglass fabrics is E-glass, which is strong and moderately stiff. Fiberglass is good as a thermal and electrical insulator and is reasonably strong, but significantly heavier and less stiff than carbon. Many weights of cloth are available depending on the application. Usually a fiberglass mold is made using glass mat and vinyl ester resin; however, in the case of an epoxy-glass mold, one would use a woven glass fabric. Glass fabrics are easily cut with good shears.
Aramids (commonly referred to by the brand name “Kevlar”) are strong in tension and moderately stiff. They have extremely poor strength in compression, but extremely high strength in shear. They are therefore used where skid-protection or shrapnel containment is necessary. They find some use in the lining of section of rocket airframe where catastrophic failure which may result in shrapnel may be present. Aramids are difficult to cut in the dry state and difficult to cleanly trim or machine when cured in a matrix. In the dry state, the best method of cutting is with well-sharpened high-quality shears, and patience.
The team has experimented before with fabrics that combine both carbon and aramid fibers in the weave. Generally this hasn’t been found particularly useful, as the aramids reduce the overall stiffness and compressive strength without adding any benefit that couldn’t be otherwise more efficiently achieved by including a separate aramid layer in the stackup.
Glass fibers and carbon fibers are also produced in mat form, where the fibers are randomly oriented and loosely packed together. The fibers are lightly bound to each other by a “size” adhesive, which dissolves in the resin upon lamination. Glass mat fibers typically have a size which is soluble in polyester and vinyl ester, but has poor solubility in epoxy. Carbon mats usually get a size which has better solubility in epoxy. But the type of size can only be definitely ascertained by contacting the manufacturer. Glass mat in heavier weights (1.5+ oz/yd²) is predominantly used in combination with vinyl ester when making fiberglass molds. In low weights, glass and carbon mats are usually called “tissues” or “surfacing veils”, and are useful when a very smooth surface is required on a part without the use of gel coat. As an example, an 0.7 oz/yd² glass surfacing veil has been used for the interior surface of the restrictor; weights down to 0.3 oz/yd² are readily available.
There is not much "theory" to selection of weave in typical rocketry usage. One usually wants twill or satin weave, and not plain. Plain weave is difficult to use on anything other than flat plates or large cylinders. Twill or satin will conform to bi-directional curves much better. Satin is most generally useful, especially in harnesses 5HS to 8HS. The tow count -- 1k, 3k, etc -- often seen associated with a weave is the number of fiber strands in each tow of the weave (a tow is a single fiber bundle -- multiple tows are woven to form a weave). So the tow count is directly related to the fiber areal weight. (Fiber areal weight -- FAW -- is the mass of fiber per unit area, usually quoted in oz/yd² or g/m². The unit g/m² is often written “gsm”.)
Fumed silica (also known by brand name “cab-o-sil”) is a filler powder used to thicken epoxy resins. It is lightweight and confers thixotropic (shear thickening) properties on the resin, making it very useful in all potting, filling, and surfacing applications. Epoxy filled with fumed silica creates a hard, sandable surface. Sometimes microballoons are added to either reduce weight or weaken the surface (to make sanding a little easier).
Glass microballoons are a powder consisting of small hollow glass spheres. The hollowness makes them extremely lightweight. They are useful in potting applications where weight minimization is important. Microballoons are not as strong as fumed silica, and do not thicken the resin as effectively, therefore they are often used in combination with fumed silica.
Talc powder (a magnesium silicate) can be used as an epoxy filler. It is heavier than fumed silica and makes a surface which can be very difficult to sand. Therefore, it is not commonly used in applications where a surface finish is desired. However, it does improve smoothness of the filled resin, so sometimes a small amount of talc may be added in a surfacing application.
Milled or chopped glass fibers are readily available. They are simply E-glass fibers which have been cut to very short lengths. Milled fibers are short enough to look like powder, but will significantly strengthen the resin when used as a filler (at a cost of more weight). Chopped fibers are usually ⅛” to ¼” long, and greatly strengthen the resin, but it is difficult to spread a resin smoothly when filled with chopped fibers. Therefore, milled fibers are more often useful, particularly as an additive in mold surfacing when high strength is required (at the cost of more sanding time). The CalSTAR team has utilized this in the past by impregnating JB weld adhesive with Carbon Fiber shavings.
Chopped carbon fibers are usually produced by the team, simply by repeatedly cutting scrap carbon fabric. They are useful for rapid repair in potting and filling applications. When onsite during a test or launch day, it is useful to have on hand a quantity of chopped carbon and fast-curing epoxy, to rapidly mix up a high-strength potting compound to apply to fill damaged areas which will cure within a short time period. Resin filled with chopped carbon can be difficult and messy to control, as the fibers tend to clump together and not flow.
Bondo is a well-known material among hobbyists and amateurs. It is notable for being weak, brittle, and difficult to control. In particular, its cure time and hardness is highly sensitive to mix ratio with the catalyst. When applied as a filler to a mold surface, the Bondo is much weaker than the rest of the surface; this discontinuity in strengths makes it difficult to achieve a smooth and continuous surface during sanding. Bondo is composed of a polyester resin with a weak filler powder, and will dissolve styrene foams. No one knows precisely why Bondo remains popular, but year after year its ill-advised usage has punished the production schedule of many rocketry and other competition teams alike. It is strongly recommended that Bondo not be used.
Special dispensation is made for a particular Bondo product called “Professional Glazing & Spot Putty”. It has a finer grained filler than general Bondo, and can be useful in the single specific case where one wants to fill tiny pinholes in mold surfaces -- in this case the goal is explicitly to have a weak filling agent, so that any excess filler remaining on the surface surrounding the hole can be easily sanded off later with a fine paper, and not risk damaging or mis-shaping the rest of the surface. A common mistake is to forget that the filler is a two-part system: it must be mixed with a hardening catalyst in order to cure. UV-curing putty is available, but it can be difficult to achieve full and consistent cure; therefore, the UV-curing material is also not recommended.
Urethane foam is the standard for mold making. In general, the higher the density, the better will be the mold. Cost scales directly with density; there are trade-offs to be made. Typical densities availale are 6, 10, 20 lb/ft^3. High quality parts have been made with 6 lb/ft^3 foam, but 10 or greater is preferred, as it will improve fidelity and reduce the coating/sanding effort considerably.
Urethane foam sands well and is reasonably strong. In lower density (6 lb/ft^3) take care not to puncture the foam, as its compressive strength isn’t too high. The foam is somewhat brittle and should not be dropped from too high or danced upon too enthusiastically. Urethane foam is compatible with both epoxy and ester resins. Slabs may be bonded together with either of these agents, or urethane Liquid Nails, or Gorilla Glue. When bonding slabs, make the adhesive layer as thin as possible -- otherwise it will be a hardness discontinuity that interferes with machining/sanding.
Polystyrene foams are cheap and readily available. They usually come in 1” thick boards meant for building insulation, but can be sometimes purchased thicker. There are two basic types:
● Expanded polystyrene (EPS)
● Extruded polystyrene (XPS)
EPS is composed of many beads fused together, and is horrible to sand / mill / shape. It is usually white, and often used in molded shipping boxes or packing peanuts. XPS is much better for sanding and shaping, and comes in colors blue or pink (there is no significant difference between XPS in the two different colors). Both typically come in 1-2 lb/ft^3 density: very light and very low hardness.
Over the years, polystyrene has been used to make a number of molds for FSAE and CalSol, two other competition teams on campus. These generally have been of low quality and time-consuming to produce. Polystyrene has the twin disadvantages of being very difficult to sand smooth, while also being incompatible with all polyester resins / fillers (these resins include styrene monomers in their formulation -- clearly, then they will dissolve styrene foam).
TO-DO
For the most part, one uses special epoxy formulations for adhering composite parts.
9309 is a high-strength structural epoxy adhesive. It is similar in many respects to 9396, but has a special filler allowing it to bridge gaps up to 0.030” and create good fillets with honeycomb core. It has a lower glass transition temperature than 9396, therefore it can be debonded with a heated blade when necessary. One generally does not add extra fillers to 9309. It has a Tg = 130°F and service temperature up to 160°F.
DP4X0 is a high-strength epoxy adhesive with a minute pot life indicated by the value of x and 24 hrs to full cure. Pot life options include 20 minutes, 60 minutes and 90 minutes. Recommended for all general purpose bonding when fast cure time is desired. Excellent for trackside repairs. While it can be filled with milled or chopped fibers to increase strength of a repair patch, this may make it brittle and thus more prone to failure. It also comes in a "NS" or "non-sag" variant which is good for applications such as creating fin fillets.
9396 is discussed earlier in this document as a laminating and potting resin, but is repeated here. It is specifically useful as an adhesive in high-temperature locations (service temperature up to 350°F). It can be moderately filled with fumed silica to bridge bond gaps between 0.020” - 0.030”, and needs no filler at gaps less than 0.015”. Because 9396 is quite linearly rigid, a good bond joint design becomes more important wherever peel failure is a concern. As one of the stiffest resins available, with reasonably low viscosity, 9396 is particularly good as an adhesive whenever the primary design requirement is stiffness and a definite 0.005” - 0.008” bond gap can be obtained.
Decent results can be achieved with adhesive epoxies available from hardware stores. Devcon brand epoxies have been used successfully and are recommended. However, 9309 or DP420 will still be superior in strength, stiffness, and repeatability.
TO-DO
TO-DO
TO-DO
TO-DO
TO-DO
Shears are not scissors. Shears look like big scissors, but they’re better. Good shears are sometimes marketed as carpet and upholstery shears. They have an adjustable pivot screw to control pressure between the two blades. The blades are of alloy steel and hold an edge. Shears need to be sharpened from time to time. Correct sharpening technique is essential to maintain close contact between the two shearing edges. An example of good shears is shown from the MSC catalog below.
The most effective saws for cutting fiber composites tend to be toothless steel disks impregnated with diamond powder. These are commonly available, marketed as tile-cutting saws. They can be purchased in sizes which fit Dremels, grinders, tables, etc.
High-speed steel drill bits will go dull fairly quickly when cutting fiber composites. Cheap ones can be sacrificed for simply punching holes. Machinists will not thank you for using their good precision drills to cut composites. Carbide bits are preferred, as they will last longer and cut cleaner. High precision (diameter tolerance < 0.001”) holes are readily achievable in composites with carbide reamers.
If a composite part is to be cut or shaped in a mill or router, the cutter should preferably be carbide, with a titanium nitride coating. Again, machinists will not thank you for dulling down their general-purpose high-speed steel cutters on composites. Sacrificial bits may be used to ease their pain with prior request to the team.
A standard stock of sand paper includes 60, 100, and 200 grits in dry sanding paper; 100, 200, 400, 600, 800, 1200 in wet sanding paper. Higher grits go dull quickly; in any grit, the paper must be replaced with some frequency as it goes dull. Discard dull paper -- this is not the place to be miserly.
Scotch-brite pads come color-coded in different levels of aggressiveness of abrasion. It is usual to keep a stock of green pads (aggressive) and light gray pads (very soft). Note that some other colors of scotch brite are “tan”, “gray”, and “dark gray” -- not to be confused with “light gray”, which is almost white in color. Like sand paper, scotch-brite goes dull with continued use, and should be discarded.
Single edge razor blades find innumerable uses in composites manufacture. They are cheap and disposable. It is usually worth the extra money to get precision edge stainless blades, which will hold an edge sharper and longer than the standard blades. Blades should be disposed of frequently as they go dull. Proper disposal requires a sharps box of some sort.
TO-DO
Before bonding two surfaces together, it is critical that they be properly prepared. The goal is to achieve three qualities:
Cleanness -- no interfering grit or organic particles
High surface area -- increase surface area with texture
High surface energy -- increase the molecular adhesion between the surface and the glue
When bonding a fiber composite surface, the goal is to achieve scratches in all directions in the plastic matrix only. Carbon fibers, in particular, are poor bond surfaces, therefore one does not want to sand into the fiber. (If you see black grit, you’ve gone too deep.) Green scotch-brite pads are an effective abrasive to achieve scratches in the matrix without attacking the fibers underneath. Scratch the surface thoroughly in all directions, either with swirling motions ~1” in diameter, or by scratching at 0°, 90°, +45°, -45° in succession.
When bonding a metal surface, sand paper may be necessary to achieve good scratching. 200 grit dry sanding is effective, again moving either in 1” swirls or a 0°, 90°, +45°, -45° succession of sanding directions.
Clean the surface well with degreaser and water, then isopropyl alcohol. For stubborn surfaces, acetone may be necessary, always check to ensure that the surface is acetone safe before using acetone.
Prior to bonding, the quality of the surfaces can be tested by putting a few droplets of water on them. If the water spreads out into a thin film, then the surface energy of the part well exceeds the surface tension of the water. This is a good sign, indicating that high surface energy has been achieved, and the bond will be good. If the water balls up, repelled from the surface, then the surface prep steps must be repeated.
Bare aluminum in air rapidly forms an oxide layer which bonds poorly. However, if this natural oxide layer is replaced with a special chromate one, the aluminum-to-epoxy bonds is one of the strongest you can get. Therefore, after mechanical abrasion and cleaning, the aluminum is to be etched with West System 860. While still wet after etching, the second part of the 860 system is applied, which puts down a chromate layer. This protects the aluminum surface from oxidation for several hours. In this time window, the bond should be made. A respirator with good filters is recommended while applying the chromate.
Note that anodized aluminum is a very poor bonding surface, and should be completely removed. This can be time consuming.
Also note that there is a more permanent alternative to West System 860, called “iridite” or “alodine”. This surface coating makes for excellent bonds, and does not have the same restriction on time frame for bonding. (The alodined surface is good for adhering to paint as well as epoxies.)
When the goal is to have a material not stick to a surface (i.e. a plug or mold), it is again critical that the surface be properly prepared. The goal is to achieve three qualities:
Cleanness -- no interfering grit or sticky particles
Low surface area -- keep the surface as smooth as possible, i.e. a mirror-finish
Low surface energy -- decrease the molecular adhesion to the surface
Flash from previous uses of the mold should they be present, should be mechanically removed. A soft scotch-brite pad (light gray) is helpful. Be sure not to scratch the mold. If aggressive cleaning is necessary, use a degreaser with water, then acetone. Otherwise use isopropyl alcohol with a towel. Blow off dust and repeat wipe-down until thoroughly cleaned.
In situations where a mold is not used, but you are interfacing a carbon fiber layup with a surface which eventually you do not want the carbon to be bonded to, following the same steps as above but replacing the mold with your surface. Remember that it is always better to be sure of what you’re doing but slower than to work quickly and risk damaging or destroying the surface.
Use Meguiar’s mold release wax or Part-all paste wax. Apply a thin light layer over the whole surface with a microfiber towel. Let the solvents flash off 5 minutes, then buff in the wax until shiny with a clean microfiber. (Buffing well is important -- a shiny waxed surface will release well, whereas a hazy texture of wax can actually act as a mild adhesive!) Repeat a minimum of 3 coats. The mold release wax provides a strong, low surface energy barrier between the mold and the part. It fills and smooths pinholes and tiny scratches. Often, mold release wax only needs to be applied the first few times a mold is used -- after that, the mold becomes “seasoned”, with plenty of wax permanently impregnated into the surface.
Before applying mold release film, but after waxing, the quality of the release surface can be roughly observed by putting a few droplets of water on the surface. If the water balls up, then the surface tension of the water exceeds the surface energy of the mold. This is a good sign, indicating low surface energy has been achieved on the mold, and it should release well. If the water spreads out in a thin film, this means the surface must be improved, either by better waxing or (more likely) by stripping off the wax (with acetone) and sanding the surface smoother, then clean it again and re-wax.
Mold release film is applied every time a mold is used. It is applied as a thin liquid layer which hardens into a polymer film no more than a few microns thick. It provides a breakable layer and a geometric offset between the mold surface and the part, allowing for easier release. Dampen a towel with mold release and wipe on a single layer covering the full surface. Rewiping over an area will only dissolve the previous release and is therefore unnecessary, but not harmful. Again, understand that the mold release film is a very thin coat.
In a typical application, where a male plug is to be made, and then a female mold produced off of the plug, the essential steps are:
Urethane foam slabs are bonded together into a larger block
The foam is machined by a CNC routing shop off of CAD geometry
The machined plug is sprayed with a polyester-based hard surface coat (e.g. Duratec or Gel-Coat)
The coated plug is sanded smooth and polished
The female fiberglass mold is laid up on the plug
For a nosecone of size, say, 13” in diameter, expect step (1) to take two person-days, step (3) to take two person-days, and step (4) to take six person-days. The schedule for step (2) depends on how quickly you can get the CNC shop to mill the foam and send it back. Making the female mold (step 5) is discussed separately in this document. The bottom line to be very aware of is to start early! The time estimates above are deceiving, because:
● These estimates are for experienced workers. Students new to the process will be slower, with greater risk of damaging plugs and then needing to repair them.
● All curing processes have inherent downtime while you wait for resins to harden. This compounds the time cost of any unexpected repairs.
● The other time constraints on student schedules -- you really need full workdays to be most effective, and these only happen twice a week.
It is worth checking the mass of a given foam plug in CAD, to understand how many people will be needed to move it around as it goes through the various processing steps.
MORE DETAIL TO-DO
The following outlines the process for making a 2-part fiberglass mold
Necessary Supplies:
● ⅛” Particle Board
● Thick Fiberglass Mat
● Vinyl Ester Resin / MEKP Catalyst
● Oil Based Clay
● Hot glue gun
● 2-3” paint brushes
● Plastic hemispheres
● Gel coat
Outline of steps:
Build dam separating the two halves of the mold
Gel goat first side
Lay-up fiberglass on first side
Tear down dam
Gel coat second side
Lay-up fiberglass on second side
Pull mold off plug
Outline of steps:
Prepare mold
Prepare materials: carbon plies, peel ply, breather, dropcloth, vacuum bag
Wet the carbon
SafeLease the mold
Lay up on mold surface
Vacuum seal part and vacuum part
Cure
Remove part from mold
TO-DO
TO-DO
TO-DO
TO-DO
Some useful books and articles are compiled in the table below.
This is a rough and incomplete list of composites-specific suppliers that may be used.
Fins can be attached with a fin jig. This method involves epoxying the fins onto the motor mount, at equal spacing, through slits made on the main booster tube. We ensure that the fins stay perpendicular to the airframe by using a fin jig: a lasercut "spacer" that holds the fins in place while the epoxy dries.
Fin jigs are used for fin sizes where epoxy adhesion is sufficient. For larger or heavier fins (here we used fiberglass), it might be best to use fin brackets.
To be added later: schematic of fin jig (emphasis on the hole for the rail button), epoxy used, carbon fiber fillets, circle clamp, sanding fillets.
As stated above, fin brackets are convenient for larger and heavier fins where epoxy is not strong enough. A fin bracket is typically an L-bracket that gets bolted into the side of the fin and the airframe. We have not had to use fin brackets yet.
A fin can is a single-piece setup that includes all the fins attached to a cylinder that slides onto the booster tube. We have also never used this method.
To quote:
High performance rockets put a huge amount of stress on the fins. Large heavy rockets put large amounts of torque on the fins and high speed rockets can cause the dreaded fin flutter. All large rockets subject fins to high forces on landing.
Reinforcing wooden fins with fiberglass or other composite reinforcement helps to make them stronger. (G-10 fins generally don't need reinforcement for strength.) However, for very high speed rockets, you also need to stiffen fins and carbon fiber makes an excellent reinforcement for this purpose.
Fins can be covered with appropriate reinforcement before being mounted to the body. This will make the fins stronger and stiffer. For conventional rockets with motor mount tubes smaller than the body tube, the fins are bonded at three points: outside the MMT, inside the BT and outside the BT. However, for minimum diameter rockets, the fins are bonded only at one point: outside the BT.
For minimum diameter rockets, it is desirable to reinforce the fin/BT joint for strength. In addition, because minimum diameter rockets are often high performance, it is desirable to stiffen the fins as well. The best way to do this is to laminate the fins tip-to-tip with carbon fiber and fiberglass. By laminating the fins tip-to-tip (and over the body tube in between), we reinforce the joint, stiffen the fin and make a solid fin can.
How to design fins that do their job while imparting minimum drag, weight, and risk
Root chord - edge of fin attached to body tube
Tip chord - edge of fin parallel and furthest from body tube
Leading edge - the edge facing the front
Trailing edge - the edge facing the rear
Semi-span - distance from the root to tip chord
Aspect ratio - ratio of a fin’s span squared to its area
Taper ratio - ratio of tip to root chord lengths
Root chord: ~2 diameter lengths
Tip chord: ~ 1 diameter length
Semi span: vary this dimension for appropriate stability
Fin tabs: make contact with the motor tube and typically between two centering rings.
Placement: close to the back of the rocket between two centering rings.
Material: The main options for the fin material are plywood, fiberglass, and carbon fiber. The material depends on the rocket being made and the durability needed.
Fillets: Create fillets between the fins and the airframe using epoxy. This will increase aerodynamics while ensuring the fins are reinforced.
Sanding edges: Sand the leading edge and tip chord of the fins to decrease air resistance and increase aerodynamics. This is optional, but highly recommended.
Check the Airframe OpenRocket tutorial to learn about adding and designing fins in OpenRocket.
As the rocket flies at high speeds, the fins will vibrate. For lower speeds, this is not a problem because the amplitude of vibrations will decrease from the air. This is problematic when the rocket speed exceeds the maximum fin flutter speed at which point the air will amplify oscillations to the point of destroying the fin. The maximum fin flutter can be calculated from the following formula:
Flutter speed (Vf) - max speed before the fins break
Shear Modulus (G) - amount of deformation associated with a certain amount of force
Speed of Sound (a)
Wing Thickness (t)
Root Chord (cr)
Tip Chord (ct)
Semi Span (b)
Air Pressure (P)
It is important to dimension your fins so their maximum fin flutter lies above the maximum rocket speed.
Thicker fins are more structurally stable, but they also increase the weight of the rocket and the drag experienced during flight. The force of drag can be calculated with:
Drag Force (Fd)
Air Pressure (p)
Velocity (v)
Drag Coefficient (cd) - how well air moves around the fins
Area (A) - increases with more thickness
The drag coefficient can be lowered by improving the cross sectional area of the fin. Cross sectional areas include square, rounded, and airfoil in the order of lowest to highest performance. The fin thickness should also account for fin flutter as a low thickness can risk damaging fins during flight.
The primary purpose of fins is to correct the rocket during flight such that it continues on a stable trajectory. In order to do this, the center of pressure should lie below the center of gravity. This is so the rocket is stabilized or pointed upward if there is a deviation from the stable configuration. The center of pressure is the sum of the pressure field on the rocket, which creates a lift force.
Stability (S) - measured in cals
Center of Pressure (CP) from the front of the rocket
Center of Gravity (CG) also from the front of the rocket
Rocket diameter (d)
As a general rule of thumb, the stability should fall between 1-2 cals. Below this range, the rocket may not correct itself enough. Above this range, the rocket may overcorrect. By increasing the surface area of the fins, the center of pressure will move towards the aft end and increase the stability.
See this detailed link for information:
Aspect Ratio (AR) =
Taper Ratio (λ) =
Wing Area (S) =
Pros of sheet metal screws
Cons of sheet metal screws
Simple
Limited number of uses
Slightly cheaper than alternatives
Less reliable / reproducible
Little upfront work
Require significant rework after max uses
Fairly accepting of too-small holes in soft materials
Difficult to size holes for in rigid materials
Title
Author
Where to find
Comments
ME127 reader: Design and Manufacture with Composite Materials
Multiple, compiled by Prof. Dharan
Needs to be Sourced
Concisely combines information from various textbooks and guides into one composites bible
Fiberglass and Composite Materials: an enthusiast’s guide
Forbes Aird
Purchase if need be – pdf is being sourced
Straightforward, covers all the basics in resins, fabrics, layups, tools, processes
Surface preparations for ensuring that the glue will stick in bonded composite structures
L.J. Hart-Smith
Search engineering articles database
Essential reading on bond prep of surfaces
Adhesively bonded joints for fibrous composite structures
L.J. Hart-Smith
Search engineering articles database
Essential reading on bond joint design and why bonds fail
Mil Handbook 17-2:
POLYMER MATRIX COMPOSITES
MATERIALS PROPERTIES
US Dept of Defense
Extensive list of tested material properties for various fibers and resins
Mil Handbook 17-3:
POLYMER MATRIX COMPOSITES
MATERIALS USAGE, DESIGN, AND ANALYSIS
US Dept of Defense
Overview of most practical composites matters. Most common standard reference in composites world
Handbook of Composites
edited by S.T. Peters
Good combination of theory and practical knowledge
Principles of Composite Material Mechanics
Ronald F. Gibson
at engineering library
Current ME 127 textbook, lots of theory
Tensile Properties of Glass Microballoon- Epoxy Resin Syntactic Foams
Nikhil Gupta and Ruslan Nagorny
Properties of epoxy-glass microballoon potting compounds
Supplier
Location
Link
Comments
Tap Plastics
Stores throughout Bay Area, one close to garage
Close to RFS, fairly limited selection
The Composites Store
Southern California
ACP Composites
Livermore
Douglas & Sturgess
Richmond, close to garage
Tutorials specific to the Avionics subteam
Applicable to club or personal rockets
Rustoleum 2-in-1 Paint+Primer has worked fine in the past; generally people use spray paint to paint rockets.
Always wear a P100 respirator when using spray paint! Spray paint can cause serious lung damage, brain damage, cancer, and more.
Environmental conditions matter when it comes to paint. Ideally, paint on a dry day with no wind and a relatively comfortable temperature. If there is wind, paint such that the part is downwind of the can/you. Colder temperatures may mean you will have to wait much longer for paint to dry. Excessive humidity can also affect your finish; try to avoid painting when it is raining or about to rain.
Prepare surfaces for painting. For fiberglass parts, this means clean with isopropyl alcohol / water mixture, sand lightly with 100+ grit sandpaper, and then clean off dust with tack cloth or more IPA mixture.
Apply a light coat of "primer" (may also be paint+primer). No need to use the same color that your final coat will be, but choose a light primer color if you want a light-colored part.
Apply one to two more light coats of primer, waiting about a minute in between each coat. Do not worry about completely covering all spots, but do your best to apply a thin, even coat. Follow the instructions on the can with respect to distance from the part.
Wait the required amount of time (usually 24 hours) for the base coat to dry
Apply 2-3 coats of the final color you want, about one minute apart. Do your best to avoid spending too long on one spot; it's easy to apply another coat, but it's hard to undo a puddle or run!
Wait 24-48 hours for the outer coat to dry
Apply 2-3 light coats of clear coat, moving slightly more slowly on the last coat to achieve a glossy finish. The clear coat will protect the paint underneath.
Installing and using KiCAD for editing schematics, layouts, symbols, and footprints.
This also contains instructions for each system.
The KiCad tutorial is actually pretty good, so in general refer to it. The Avionics intro project (on Gitbooks) guide also walks through usage of KiCad.
Use the following link to learn how to make new symbols for components when you can't find an existing symbol for it in the KiCad libraries.
Often, it can be worth finding an existing symbol that is similar (for example, an older version of a sensor), copying it, and modifying it.
Try to make symbols following a functional pattern of placing pins. Symbols don't need to look like the footprint of an IC. Often, symbols of ICs will have all Vdds/Vccs/Vddios at the top, all Vss's at the bottom, and pins on the sides of the symbol.
STAR has has a repository hardware-sch-blocks
which contains a library of symbols, star-common-lib
. Create your symbols in this repository on a new branch, add them to the library, and when ready submit a pull-request. Make sure to update the datasheet link and description!
As with schematic symbols, try finding an existing footprint and then modifying it according to the actual component's datasheet. Datasheets will have drawings and dimensions of the footprint, often under a section such as 'Packaging'.
Many ICs come in standard packages (such as SOT-8). KiCad includes footprints for these standard packages, so often one can select one of these and then ensure with the datasheet that it matches--unfortunately, different manufacturers may use the same name but actually have slightly different footprints.
As with symbols, all STAR footprints go in star-common-lib
in hardware-sch-blocks
. Create your footprints on a new branch (makes sense to put them on the same branch as the new symbols), and submit a pull-request. Please let the current Avionics lead know when you submit a pull-request so it doesn't slip through their email.
Download KiCad from here:
To jump right in, go to and then .
If you've made your own schematic symbol for a component, you will likely have to make a footprint for it as well. Footprints are described . The following link will show you how to make new component footprints.
Avionics uses Trello for project management
Probably best said by Trello itself.
Trello is a project management software which allows us to track tasks which need to be done, what stage projects are in, and what everyone is working on. It helps streamline our workflow by making sure we always know what we have done, what we are doing, and what we have left to do.
Create a Trello account and message the Avionics lead to gain access to the above Trello team for Avionics.
Learn git and avionics' git workflow
You'll find all of Avionics' sources on our Github, including schematics, layouts, firmware, and software. This Github org also contains repositories of other STAR subteams.
Windows 10 supports running a proper Linux development environment using Windows Subsystem for Linux. Installing and using this is highly recommended on Windows.
Make sure you have a Github account and you have joined the Github STAR org Avionics team by messaging the avionics lead (currently Cedric Murphy @Andalite1999#4769). For git installation, see here.
There are many great git guides out there!
Learning git takes time and can be intimidating! If you are worried you're about to mess-up your repo, or have already messed up your repo, ping someone in Discord!
Short list:
Clone the repo.
Create a new change branch from the master branch.
Make changes.
Rebase onto master branch.
Submit a pull-request on Github.
When approved, merge into master!
Clone the "repo" onto your local computer in by running the following command in terminal:
This will copy the repo and all its current files into your directory. Make sure to read through the relevant documentation in the repo before making any changes.
The --recurse
(short for --recurse-submodules
) tag tell the computer to execute
after cloning. For libraries that are used in multiple repositories, such as hardware-sch-blocks,
it is cleaner to create a separate repository for the library and embed it as a submodule instead. Because submodules are not normally downloaded with git clone, --recurse
is necessitated. For a thorough guide, see tutorial.
A branch is a separate copy of a git repo that can have its own changes separate from other branches. A branch can later be incorporated back into the "master" (main) branch. We use branches to develop and test changes before we merge them into master, which we expect to remain stable and flight-ready.
Create and checkout a new branch:
Switch to an existing branch:
Edit or create files with your desired text editor, which should be vim.
Register changes with git using git add
. For example if a.txt
is a new file and b.txt
is a modified file, do:
Then, "commit" changes into git. This saves changes into a snapshot which you can look back at.
Often you will work with other members on a change on a given branch, so the new changes (the commits) on the branch will need to be pushed to Github. Do this by running:
The first time you do this from a new branch, git will tell you that no remote exists. Follow the instructions it outputs to create the branch on the Github side.
Often, there will be many commits on a branch. To keep git history on the main branch concise and informative, we often squash the commits on a branch into a single commit that describes the whole change. There are two primary ways of doing this:
or
While squashing changes gives a single commit that describes the entire change of a branch, rebasing onto master ensures linear commit history of the master branch in case there have been changes on master since your change branch was created. Rebasing does this by essentially taking the current master branch and replaying all your changes on the change branch onto the new master. Rebase onto master, once commits are squashed, by doing the the following from the changes branch.
You may encounter rebase errors here depending on what changes ocurred on master. Git will let you know which files you will have to merge manually and how to continue when done fixing.
Make sure to test all functionality again after rebasing onto master!
Finally, the change is implemented and tested. A pull-request is where the final review of the change is done before it is merged into master.
To submit a pull-request, do a final git push
and then go to the Github website. Select the branch and using the Github UI select submit pull-request. Add relevent reviewers and ping them on Discord.
As reviewers comment, you will likely need to make changes. Once all changes are made and reviewers approve the change, hit merge!
Some commands you will find useful.
Show commit history:
Optional: Download http://leo.adberg.com/gitconfig and save as ~/.gitconfig (replacing user info) To see a view of all commits and branches:
To see the status of your local repo, you can run:
These slides have nice descriptive diagrams! Check it out!
Setting up ground station software to run on laptop
First, install npm
. Then, run $ npm install
. This will take a while as there are many dependencies for the ground station software.
If your terminal fails on
try uninstalling and reinstalling node.js.
If you are getting a git error such as
try running npm cache clear
.
If you are on Windows and are installing npm
in WSL, npm
will likely fail if you have npm
also installed in Windows itself. Install npm
in only one of the two.
To run the program, you will first have to plug in the ground station and then determine which device the ground station is.
On Windows, open Device Manager
, look under COM Ports
. Remember which are listed, and then unplug ground station. The Device Manager will refresh and, if the ground station was correctly detected by Windows, one of them will have disappeared. You can plug ground station back in for it to reappear. It should have a name in the format COMx
where x
is a number. If you installed npm in Windows, you will run the ground station software with the command npm start COMx
. If you install npm in WSL, you will run the ground station software with the command npm start /dev/ttySx
where x
is the same number as in Device Manager.
Make sure you have logs
folder in that directory or else this will fail!
Open up a web browser and go to http://localhost:8080. If opening this gives you a blank page, inspect element
. If the error says something along the lines of cannot find dist/openmct
then...we really don't know. For now, contact someone who has it working to email you their openmct
package. Then from ground_station_openmct/node_modules
run rm -rf openmct
then unzip the emailed openmct package into ground_station_openmct/node_modules
.
Reviewing is one of the most important parts of bringing up a board – we don’t want to waste money or time on a flawed design. Consequently, it can take practice to really know what to look for while reviewing a board; there’s no substitute for watching an experienced engineer at work. However, most boards we make have quite a bit in common, so a lot of failure modes are also shared. For anything simple, the below guide should be a good starting point; for anything analog/RF, high-speed, or high voltage/power, additional care should be taken.
In general, when reviewing a board, make notes and open issues on whatever issue tracking system you’re using (GitHub, Jira, etc.). Let the responsible engineer (RE) review those issues and make changes – don’t make changes on your own. Especially with schematics, merging changes from multiple people can get messy.
Reviews take time to be done thoroughly, so (especially if a single person is doing the review), alot time in terms of days, not hours. Additionally, do not think of a review as a 'final check' before a board is put out for fabrication. It may take weeks to make changes and update until a board passes review.
Make sure you include the schematic file (and layout if applicable) as well as a bill of materials (BOM) that includes DigiKey part number (or Mouser #, or direct link if applicable), name, quantity, and price for literally everything on the board.
At the level of the board, one of the first steps is to ensure that all interfaces to other systems are met. This usually means that there should be power, a programming port (per MCU), and some combination of actuators + sensors + communication. Familiarize yourself with the function of the board within the system. The project page for the board or the system it is part of should contain the description of these functions against which you can compare the schematic.
Component level review should be exhaustive. This means pulling up a datasheet for every single component other than simple passives, and comparing side-by-side with the schematic. Things to look for:
Reference designs (in the datasheet) are followed
Directionality of I/O lines
Acceptable voltage ranges
Power lines
Every Vdd/GND pair should have a decoupling capacitor whose value matches what’s suggested in the datasheet
Analog power should be separated from digital power (sometimes with additional filtering on the analog lines).
Certain types of I/O (I2C buses, for example) require pull-up or pull-down resistors. If you’re not sure where these are required, ask.
Sometimes, components will have requirements on where they should be placed during layout (for example, decoupling caps should always be placed near the IC being decoupled). Make sure these are annotated on the schematic.
Lastly, at the system level, you should ensure that your power block can supply enough current/power to meet the peak needs of everything on the board, with overhead. Also ensure that top-level interfaces to other parts of the system are satisfied.
TBD
How to design a schematic and layout for PCBs
Some parts of this page may be out of date (in particular, the section "Before You Submit"). The rest of this page is a great reference!
Please note that there is a board design DeCal that can give you a more detailed understanding of how to build PCBs: https://decal.berkeley.edu/courses/4529. Though this tutorial will follow the format of the decal's website, this page is just an introduction. You can access the syllabus and material at this link: https://ieee.berkeley.edu/hope/pcb.html. Here is another useful resource on PCB design: http://www.ti.com/lit/an/szza009/szza009.pdf
Board design "useful tips" document from the aforementioned board design decal: https://docs.google.com/document/d/1sA1MmZkygvkN0kvH0_EiXm4IRMi5ilCOcb7CaAVOmxY/edit
A printed circuit board, or PCB, is the backbone of hardware design. These cheap, compact, reliable boards allow us to implement circuits into a greater system. They are better than alternatives in that they provide form (hold everything together) and function (make good electrical connections). They are built from conductive copper layers separated with non-conductive substrates and include things called vias, tracks, and pads which will be discussed later. While the process of making PCBs may seem long and frustrating, this tutorial will guide you through the most basic parts of making a good PCB.
In order to start making your PCB, you will need a design. It should meet your system specifications under all relevant conditions (such as temperature or vibration) in little time for little cost with few iterations (don't worry if you have to redo your design, but don't just guess and check). Your design should be testable and fail minimally. You can start a design by identifying what particular electrical components provide which functions. These components are then put into something called a schematic, which essentially pieces these components together to make your design work.
Before starting anything else, make a specification document. This should outline exactly what you want your board to do, but should not specify implementation details. For example, a telemetry and power control board might be expected to transmit and receive data at 96 kBits/s, provide up to 500 mA at 5V for 6 hours, etc. Each of these desired functions should be testable before final deployment of the system (i.e. a function like "doesn't run out of power on the pad if there's a delay" would be better written as "provides up to 500 mA at 5V for 6 hours").
Your specification document should be roughly 0.5-2 pages long, depending on the complexity of the project. You may refer to a higher-level system architecture document, or even omit the specification document and simply use a section of a system architecture document as your spec, depending on how far design work has progressed. Make sure to also refer to the rules and regulations of whatever competition the board is for (see here for IREC); explicitly citing these in a spec document is always good.
Once you have your functionality decided upon, it's time to start developing the design a little further. At this stage, continue updating your specification document or create a new system architecture document that will contain all design choices to achieve the desired functionality.
This is where questions like "do we need a microcontroller or can this be done without one?" or "how are we going to power this board?" should be answered. As you do this, feel free to update your specification document as you realize what additional functionality is needed. At this stage, you should also consider exactly how your board may interface with other devices and people (radio, serial communication, LEDs to communicate power/status, switches, etc.)
Depending on your familiarity with the available hardware, you may not be able to fully specify the architecture before taking a look at the next section, Selecting Parts. It is perfectly fine to go back and forth between looking at available components and updating the system architecture.
Selecting parts to use for your design may seem like a tedious task, but it's extremely important to get right for your project to work. After determining your desired functionality and architecture, you know what passive component values and ICs (integrated circuits) you will need, but that is only a small part of selecting the physical part that will end up on your physical board. Here are some things to consider:
Components come in may different sizes and shapes: some are larger, some are smaller, some are impossible to solder, etc. It is extremely important to pick a correct form factor for each component, or your design will be impossible to assemble.
Solderability
How small is the component? For passives, CalSTAR uses 0603 Imperial or larger.
Does it have leads or is it marked QFN (no leads) or BGA (ball grid array - under the IC)? If the latter, you will need a reflow oven and cannot solder by hand. If absolutely necessary, QFN/LGA components may be solderable at a hot-air station; ask a subteam or project lead if you think this might be necessary.
Surface Mount vs. Through-Hole
Surface Mount (SMT/SMD) and Through-Hole (THT or DIP) are two forms the component can take. The former lies flush on the board and are usually smaller while the latter is put in a hole through the board.
Passives and ICs should be SMD, while connectors are usually through-hole. The more compact the board, the better.
Different from the component package, this is how the components are actually shipped. Make sure you can order the amount you want; some components are sold in units of 5,000! Generally, Tube, Tray, and Cut Tape and fine, whereas Tape and Reel and Digi-Reel have minimums in the thousands. See the Digikey ordering guide for more details.
When looking at an IC's application circuit schematic/layout, consider the complexity and the sensibility of the externals required. If it is not appropriate for your design, consider another IC. Many ICs require an extensive network of resistors, capacitors, etc. to function properly.
In general, while searching for parts, whether from Digikey (preferred) or Mouser or Adafruit, read the datasheet and specs carefully to ensure they fulfill the requirements you need. You need to check that is can drive the correct load, provide or handle enough current, is powered by the correct voltage, is the right size, and for passives, is the right value. Here is an example of a search for a specific 10kOhm 0603 SMD resistor from Digikey:
Microcontrollers are essentially the "brain" of the PCB. You can program them to perform specific tasks (for example, light up an LED or interpret sensor data). They are usually quite complex and have dedicated pins for their different functions. GPIO pins (General Purpose Input-Output) are especially useful for customization. CalSTAR has previously used AVR processors by Atmel (ATmegas, the same as commonly found on Arduinos), but we are now using 32-bit ARM chips made by STMicroelectronics (STM32F401RET6, for example).
Transistors are three-terminal semiconductor devices used to amplify or switch electronic signals and electrical power. There are many different types of transistors, but the most common that you'll see are BJTs (bipolar junction transistors) and (MOS)FETs, which are (metal-oxide semiconductor) field effect transistors. Transistor physics is generally not covered well in lower-division EE classes; feel free to ask someone for help picking a transistor if you're unsure.
This stack exchange post does an excellent job at summarizing when you should use a BJT versus when you should use a MOSFET.
DC-DC converters converts one DC voltage into another. For example, a 12-V battery voltage may need to be stepped down to 5 or 3.3V. There are two common types: LDO and switching regulator. The LDO (linear drop-off) is generally simpler to implement into a PCB because it has fewer external components, but it uses a lot of power.
A switching regulator, on the other hand, is relatively efficient with power and is generally more precise. These converters are important to supply the correct voltage to a component in order for it to work properly. A switching regulator that steps up voltage (at the expense of current) is known as a boost converter, while one that steps down is known as a buck converter. There are also buck-boost converters.
Passive elements include resistors, capacitors, inductors, oscillators, buzzers: anything that either consumes but does not produce energy or that is incapable of power gain (unlike a transistor that is capable of amplifying). Capacitors and inductors can used for oscillation (like a voltage regulator). Capacitors can also be used for coupling/decoupling.
These are usually LEDs or buzzers: anything that indicates a specific function is occurring. LED's are important to indicate whether power is being supplied to a PCB, for cases of safety and debugging. Buzzers can be used when the PCB is obscured (like in the rocket) and the board LED is no longer visible. Small green SMD LEDs are common to indicate power, while other colors can be used to indicate activity or danger.
A diode is an semiconductor device with two terminals that allows for the flow of current in one direction only. An LED (light emitting diode) is one example. Diodes can be used for reverse polarity protection, i.e. if you connect power in the wrong direction, current will not flow and therefore will protect your circuit. Zener diodes can also protect surges by having one terminal connected to a power net and one connected to ground.
A fuse is a safety device that prevents a short circuit from damaging the rest of the board. There are two types: resettable and non-resettable fuses. A non-resettable fuse works by allowing the overcurrent to melt a small piece of metal in between its terminals so that it becomes open. A resettable fuse has a material in between its terminals that, instead of melting, increases resistance and cuts off current flow.
These are the components that are usually soldered to the edge of the board that allow it to connect to the necessary peripherals. For example, a battery will need a connector (usually an Anderson PowerPole), while screw terminals may be used for wire connection to other PCBs.
There are many different ICs (integrated circuits) that your PCB may need in order to function. This includes sensors (like a GPS, altimeter, accelerometer, or gyroscope) to provide information about what your project is doing (in our case, what is happening during flight). In addition, a radio IC, with attached antenna, is useful for communicating commands to the microcontroller during testing and flight.
While selecting your parts, you will need to write them down. Each component requires a lot of information in order to purchase the correct one. Here is an example BOM, with the necessary columns:
The manufacturer part number is the number of the manufacturer (for example, Infineon) of the component while the supplier part number is the code of the supplier (for example, Digikey). "Ref Des" stands for Reference Designator, which is the number of the component in your schematic. Make sure that you select the correct size for all components and that their packages are appropriate for your layout. For example, make sure resistors/capacitors are 0603 and that you distinguish between through-hole and surface mount.
What is a schematic? They are drawings that represent elements in a system using abstract symbols to give information without unnecessary details. You can implement these schematics in your PCB design software, as discussed in the information notes at the top of this page. In general, signals should go from left to right, top to bottom, with higher voltages at the top and lower at the bottom. Here is an example in KiCad (the long parallel gray lines are to indicate the separation of functions in the circuit):
Notice the connector to power is at the top left and the output is at the bottom right. The amplifiers follow the "high voltage up-low voltage down" rule and everything is separated by function.
You will want to use an appropriate grid size to align your wires (about 50 mils - 1 mil is 1 thousandth of an inch, NOT one millimeter) and use labels to make the values and functions of each part clear.
Most ICs are drawn as rectangles. A resistor can be shown as a long rectangle or a zig-zag shape. Capacitors are using two parallel lines of some length, while a battery is a long line in parallel with a short one. Some shapes are made for special functions (a triangle is usually an amplifier). Here are some examples:
Sometimes you will need to make a new schematic symbol if your software doesn't provide it. Be sure to group pins on your new symbol by function, not the location on the physical package. Power should be on top, ground on bottom, and inputs on left and outputs on right.
Once you have your symbols in your schematic, you might notice they will have associated letters and numbers. For example, U1 or R4. These are called reference designators, as shown above in the example BOM. The letter tells you what kind of component it is. "U" means some IC while "J" is a connector and "R" is a resistor. The number is just clarifies which of that type it is. Naming 15 different resistors "R" isn't helpful, so they are labeled R1 to R15. These are usually automatic, but you will have to hand-label their values, of course.
When your schematic is complete, you will want to run ERC, or electrical rules checker, through your software. In Diptrace, this is done by clicking "Verification" at the top menu bar and then selecting "Electrical Rules Check" from the drop-down menu. In KiCad, it is Inspect>Electrical Rules Check. This will ensure that your wires are connected appropriately and that you didn't make any egregious errors.
What is a layout? It is like a map for how your physical board will be arranged. PCB's are built layer by layer with copper layers for connectivity and insulating layers to provide mechanical rigidity and form. The boards are covered with something called soldermask, so that when you start soldering, the solder will stay only within the exposed pads you designate. These pads are made of copper and connect to the copper layers in the board. Here is an example of both through-hole and surface mount pads with the lines of connectivity in light green (the other smaller holes you see are called vias, which you'll learn about later):
Layout begins by assigning footprints to each of the components in your schematic. Footprints are the physical representation of the schematic symbol of a component. For example, a capacitor footprint will usually be two parallel rectangles, as shown below:
There is a function in your software that allows you to import your schematic so that the footprints connect like they're supposed to. This is called LVS (layout vs schematic) and is often included in DRC (design rule check).These connections are those light green lines you see above. You can even use the autorouter to do this, but it's not a very intelligent function. It's better to do it by hand. Make sure that when you are connecting pads to one another that none of your lines cross! Your layout needs to be planar. You may find that this proves difficult, if not impossible, so to get around this, use vias. Vias, which are holes that go between the back and front of the board, need to be proportional to the width of the trace (the term for the light green lines). See the following figure. Below is a calculator for finding the appropriate width of a trace, which need to be larger to carry large currents.
When routing, use net classes (e.g. power, ground, etc), and try to keep traces short, especially for high currents, since traces have resistance. Fill zones, or copper pours (see example below), help to dissipate heat across the board and connect large areas together. Follow datasheet recommendations for help.
Once you've arranged them in a way that makes sense for your project (i.e. connectors should almost always be at the edge, with the SMT IC's near the center), consider the Design Rules. These are the minimal manufacturability requirements of the board. For example, drill sizes have to be a certain diameter, along with trace widths. The smaller everything is, the more difficult and expensive it will be manufacture, if not impossible. At the end of your design, you will run DRC, which is similar to ERC, but instead checks that you have followed all the rules of manufacturability. Here is an example of a layout:
General steps to follow:
Begin by drawing edge cuts. This is the yellow rectangle that surrounds the components. It determines the outermost edge of your board. Usually, the size of your board is dictated by mechanical requirements, so this is almost always the first thing you should do.
The other two colors of rectangle define the ground and power planes that you will be connecting your components to.
Check ICs' datasheets for a recommended layout. How much space does the recommended layout require? In the above example, U1 had a recommended layout that suggested the capacitors and diodes around it be arranged as so, with copper pours connecting them where appropriate.
Next, place the connectors at the edge of your board. In this example, it would be the USB connector (it wouldn't make much sense to put that in the middle). Place power-related components and their external components after that, according to the datasheet's recommendations. Include any fills or thermal vias that it recommends.
Place the rest of your components (usually passives and indicators) and then add any additional filled zones you may need.
Lastly, route all nets not connected to a fill zone and adjust the size of your fills as necessary after creating them. Add routes and vias to connect your fills.
Other things to consider include the following:
Traces have resistance (they will heat up, decreasing efficiency and wasting power), have inductance (current through them can't change instantaneously), and have capacitance (causes signals on one wire to show up on others). Increasing trace width reduces resistance and inductance. Decreasing trace length does the same.
Vias have inductance and add length, so put them in parallel when you must use them.
Decouple correctly by placing capacitors close to the component you are decoupling and size the capacitor correctly so that inductance doesn't dominate. See datasheets for recommendations.
If you are creating a complex with a lot of components, consider using the "Manhattan Routing" strategy. It has only one simple rule: all horizontal traces go on one layer and all vertical traces go on another layer, and traces go to the other layer (with a via) whenever they need to turn. If your board is very simple then this probably isn't worth the effort, but for large or dense boards this strategy can make your life much easier.
When you have finished your layout, go through this checklist to ensure that your board is ready for fabrication.
Make sure you have done all of the following before a review, and before boards are submitted for manufacturing.
All passives should have values visible.
Important nets should be labeled
E.g.: V_in, 3.3V, GND, DEBUG_RX, DEBUG_TX, ACCEL_SDA.
Text should not overlap.
Components that are not easily replaceable should have Manufacturer and Datasheet filled out in Component Properties.
"Not easily replaceable": ICs, connectors, fuses, any unusual components such as a massive electrolytic capacitor.
Schematic should be broken up into modules (surrounded with a box) to aid readability. Label each module with text.
E.g.: radio, voltage regulator, reset line, programmer port.
Use netports to prevent lines going everywhere.
Test points should be added to ALL nets that we MAY want to measure at some point.
Double check all patterns
Add silkscreen
Pins on ports such as UART, programming ports, actuators, etc should be labeled
Move reference designators (RefDes) if necessary
Tip: F10 allows moving reference designators, 'r' for rotate
Place board name and version (eg Ground Station v3)
Calstar Logo (use reflected version if placing logo on the back of a board)
File > Renew Layout from Schematic
Verification > Check Net Connectivity
Verification > Compare to Schematic
Verification > Check Design Rules (F9)
Use the HOPE PCB Decal checklist: https://ieee.berkeley.edu/hope/checklist.html
Use BAC's InstantDFM to verify they can produce your board within standard capabilities: http://instantdfm.bayareacircuits.com/
Impedance calculator: https://www.eeweb.com/tools/microstrip-impedance
Use to calculate impedance of traces, primarily for matching against 50 Ohms
Note: we have our boards manufactured to be 31 mils (this is the substrate height)
The substrate in our case is FR4
Trace width calculator: https://www.eeweb.com/tools/external-pcb-trace-width
Use to determine minimum required trace widths based on current range
Bay Area Circuits:
Stay within BAC's standard capabilities
Manufacturing capabilities: https://bayareacircuits.com/capabilities/
Stackup capabilities: https://bayareacircuits.com/multi-layer-stackups/
InstantDFM is a simple tool from bay area circuits that you can use at the very end of the board design process to verify that your board meets their manufacturing requirements (like minimum trace widths, via sizes, copper to edge clearance, etc). Before you submit any board for manufacturing, you should always run it through instantDFM to verify that there are no errors.
How to debug hardware and firmware problems
Start with these steps to avoid common mistakes:
Make sure the PCB is powered (either by power supply or by battery). Indicator LEDs are generally helpful for this (if they were placed correctly).
Check for correct DC voltages with a multimeter at all input pins.
Check for continuity on nets. You can also inspect solder joints.
Check regulator outputs with a DC multimeter AND an oscilloscope.
Check input voltage at all ICs with both DC multimeter AND an oscilloscope.
Check for amplitude and frequency of all external oscillators with an oscilloscope.
Check bus signals with an oscilloscope.
After you determine that the PCB is powered correctly and connections are intact, see the firmware debugging to determine more complex problems.
Prior to checking firmware, make sure the hardware is functioning as expected using the hardware debugging steps.
Then,
Sanity check you can control GPIO pins by flashing a simple program that sets GPIO pins high, and another program that sets GPIO pins low. Check output using a multimeter.
Check the fuse bits are what you expect them to be.
Check the microcontroller is running at the rate you expect it to using UART. This may be a fuse bit issue as well.
Once you have confirmed basic control of the board and microcontroller, test your firmware by adding status LEDs to show general state of code (particularly useful to check control flow in a state machine). Add additional output at critical points in the code. Forms of output include GPIO pins, radio, UART, and LEDs. This should allow you to see where your program is going wrong.
Modularize the code as much as possible and test modules from simplest to most complex. Reduce complexity in the code.
How to code in C, given that you already have knowledge of other programming languages.
A useful reference linked here.
Primitive Data Types:
int
: integer
float
: floating-point number, used to store decimals.
double
: double-precision floating-point
char
: ASCII character
In the <stdint.h>
header, additional types are included for defining integers by size (in bits) and sign. A useful one is uint8_t
(an unsigned 8-bit integer type) to represent a byte.
Computers prefer to interpret things in binary, so the use of bit operators is often useful in C to more accurately visualize what happens underneath the abstraction. The most common operators are:
These don't seem super useful on the surface, but they will be once we start dealing with registers.
The microcontroller datasheet is your best friend!
I/O devices in a microcontroller (such as sensors or actuators) are mapped to memory addresses - that is, you can get a sensor value by reading from a location in memory, or modify an actuator output by writing to another location. What does this mean for you? Embedded C handles this through the use of registers. A register is a storage element in the processor, often used to hold intermediate values during computations. However, certain specialized registers are used to perform hardware functions, and we can access these registers by using their names.
For an example, let's look at the I2C interface on the Atmel ATMega328, a common microcontroller that is famously used on Arduinos. I2C designates a master and a slave device, and the master can individually address a slave device by sending its address on the common bus line before sending or receiving data. There is also a common clock line. Taking a look at page 292 of the datasheet, we find descriptions for each register used in I2C operation.
This register holds an 8-bit value that can be read from or written to (as we see from R/W in the access line), that determines the speed of the SCL line, which is the common I2C clock. The conversion of this value is as follows: SCL frequency = CPU clock frequency / (16 + (2 * TWBR * Prescaler)), where the prescaler is set in a different register.
Let's say I want an SCL frequency of 100 kHz from a CPU clock frequency of 16 MHz. I can achieve this with a prescaler of 1 and a TWBR of 72: 16 / (16 + 2 * 72 * 1) = 16 / 160 = 0.1 MHz. I can assign this TWBR rate simply like this:
So far, so good. Let's move on.
Whoa, okay. This one's a little trickier - we have two different values here. What should we do?
Let's go back to our bit operators from earlier. If I want to get only the TWI Status Bits (that is, TWSR[7:3]), I can simply right-shift the TWSR value to eliminate the three lowest-order bits.
What if I want to write to the prescaler bits without overriding a bit I shouldn't be writing? Technically, I can't override a read-only bit even if I try, but this will illustrate my point just fine. A useful feature of the OR operator is that if I OR something with a 0, I just get that same value - that is, A OR 0 = A. But A OR 1 = 1 no matter what A is.
Now consider this code:
What does this do? I'm ORing the TWSR value with a binary value that essentially passes the top six bits unchanged - since I'm ORing with zeroes. However, I'm forcing the bottom two bits to be 1s, because as I pointed out, 1 OR anything is 1. So this code forces the prescaler to 64, per the table above, but leaves the other bits unchanged! I can simplify this a bit:
This is great, but what if those prescaler bits are already 1s and I'd like to set them back to 0s? ORing won't help, because they'll be 1s after the OR as well. This is where the AND operator comes in handy. Note that for any A, A AND 0 = 0, but A AND 1 = A.
Now consider this code:
This is a similar trick. ANDing the top six bits with ones passes them unchanged, but ANDing the prescaler bits with zeroes forces them to zero. So the top six bits don't change, but the prescaler is now 1. Let's simplify this again:
Let's say now I want to make the prescaler 16, so I want to flip the single bit TWSR[1] to 1. Rather than typing out the binary mask I want to use, we can shortcut:
This left shift operator evaluates to 0b00000010, which is exactly the mask I wanted to use. Similarly, I can flip it back to zero with this:
This produces the mask 0b11111101.
Often, each bit in a register can signify different settings for the microcontroller, and is given a name.
In the I2C control register (TWCR), each bit (excluding bit 1) defines a setting of I2C. The datasheet defines the purpose of each bit. Below is the definition of bit 2, TWEN.
TWEN defines whether I2C is enabled or not. I can set this bit using the bit shifting, ANDing, ORing, and NOTing operations.
Using the predefined names makes the code easier to read and understand, and thus more maintainable, over using raw hex values.
And there you have it! You can use combinations of these tricks to do a lot of powerful things.
For a more complete reference on the C language, see the text below:
http://www.dipmat.univpm.it/~demeio/public/the_c_programming_language_2.pdf
Getting started with the development environment for the Avionics codebase
The Container Environment section will go over setting up the tools for compiling firmware, the Writing and Compiling Firmware section will go over compiling the firmware, and the Flashing Programs to the Microcontroller section will go over writing compiled code to hardware.
Avionics distributes a container which contains all the tools for compiling our firmware. Some of the development tools we use for firmware development are a mild pain to install (particularly for beginners), so using the container is recommended for quick set up.
If you have tried out the container and have problems given your setup, and you really want to install yourself, go ahead. This is not recommended unless you are well acquainted with installation of compilers, etc.
To use the container environment, you will need to install the Docker or Podman first. Podman is the fully open source alternative to Docker, and they share the same commands format. Either can be used, although most of this tutorial will use Podman because it is easier to use on Windows.
If on Linux, there's too much variety to put anything here. I'm sure someone in avionics will want to help! Podman is very easy to use on Fedora and works out of the box.
If on Mac, this is all currently untested.
On Windows, you the recommended procedure is to install Windows Subsystem for Linux (WSL) and run Podman within it.
Since WSL is a non-standard linux environment that lacks of some important syscalls and processes, Docker cannot be run on WSL without some hassles. Podman has been tested on WSL, and you should follows the instruction below.
If your Windows 10 is Home version, you might not be able to enable Hyper-V. You should upgrade to Windows 10 Pro, or just use the free educational version from the school: https://software.berkeley.edu/microsoft-operating-system
Follow the instruction on https://docs.microsoft.com/en-us/windows/wsl/install-win10. You should install WSL 2. This tutorial is based on OpenSUSE, but it is possible to use other distros.
Once you finish, install Podman by running
Then, run the following instruction to create and modify the config file to make it run on WSL:
Then, use an editor of your choice, open /etc/containers/containers.conf
with sudo
:
Uncomment the line with events_logger
, then change the value to file
.
Uncomment the line with cgroup-manager
, then change the value to cgroupfs
.
You should be able to run the docker file right now. Note that you must run Podman with sudo
, or you won't be able to do anything. If you are getting No CNI Configuration file
error, do the following steps:
Run sudo podman network create
. It should give you a filename.
In the command you used to run docker, add --net <config-name>
after podman run
. <config-name>
is the filename you got from the first step.
The toolchains repo here has a readme with additonal information about the development environment.
First download the toolchain container image.
Then, create a directory where the files in the container will be stored.
The location of this directory can be viewed with :
Finally, create the container
Once the container is setup, it can be started with:
You can enter the toolbox to a bash
prompt with the below. This is where you will be actually running commands to use the compiler, etc.
Finally, once the container bash prompt is exited with exit
, the container can be stopped with
An alternate way to transfer files is using the Visual Studio Code editor. This may be convenient if you already use VS Code, and may be a method that works if this does not. See the VS Code & Containers
section.
To copy a file from the image to the host system (your normal operating system), you need to first get the mount point of your workspace by running
where star-workspace
is the volume name. If you use another volume name, you need to change the command accordingly. You can save it to a environment variable to avoid copying the long path every time.
Since the path is usually only accessible with root privilege, you need to copy it to a place that you can access without sudo
, like your home directory:
Then, if on Windows, open Windows Explorer, type in \\wsl$
in address bar. For every distros you install, you can see a folder with the same name as the distros in this folder. Go to the distro folder that you use to run Podman, and go to the path you copy the file to in the last step, like home/<user-name>
. You should be able to see the file you want in that directory, and you can copy and paste it to anywhere you want in your Windows file system.
If not on Windows, simply open a terminal and go to ~
. The file will be there.
To setup, install the Remote Containers extension in VS Code.
Then, go to the "Remote Explorer" tab on the left bar of VS Code, right click on the container you created in the previous step and click attach to start a VS Code instance in the container. From here you should be able to open a terminal inside the container by going to Terminal->New Terminal
and interact with the filesystem through VS Code and clone stuff, open folders, etc.
In this section we detail how to compile code into binaries which can be written onto the hardware.
'Firmware' is the code which runs on the hardware, named so because it is 'closer to the hardware' than normal desktop software.
We use MbedOS for libraries and a lot of the support code needed. The tools needed to run mbed are all included in the container. Run the commands below from the container prompt.
For most cases, you will only need the Developing STAR firmware projects section.
For documentation on the Mbed API, look at the official docs here. If you don't find a library for what you want there, look at community built libraries by searching using the search box in the upper right corner.
For more detailed documentation on Mbed Command Line Interface (CLI), look at the official docs here.
While the mbed utilities can be used directly, most often in STAR we iterate on existing STAR projects. Therefore we have abstracted away most of the mbed commands using Makefiles. Note that the specific build system can vary slightly from git repository (repo) to repository, so make sure to check the Readme of the specific project you are working on.
If you are unfamiliar with the Git version control system, check the Git Tutorial out before continuing.
First clone the desired repository from within the container, e.g.
Then from within the repository, clone the submodules and run mbed deploy
Finally, compile with a command like
Check the repository Readme for details on the command to run to compile. The output, the binaries to flash to the microcontroller, will be put in the output
folder.
To create a new project called mbed_project
, run the following:
To compile a project, run the following from within the project folder
The target, NUCLEO_F401RE
is a development board that has the STM32F401RET6
microcontroller on board, the same microcontroller unit (MCU) that we use. The toolchain selects which compiler we are using.
This should give you something like the following if it compiled successfully.
Find libraries by searching in the search bar on mbed's website. Then, once on a library's page, look at the box titled "Repository toolbox" and select the down arrow on the yellow "Import into Compiler" button.
Then select "Import with mbed CLI" and copy the command listed.
The command should be of the form mbed add <project link>
. Run this command from command line inside your mbed project.
'Flashing' a program onto a microcontroller means to write the compiled code onto the microcontroller to be run when the microcontroller is powered off and back on.
As of right now, usb-detection and programming through the container is not working. Instead install and use a utility on the host system.
Windows: Download and install the St-Link Utility from the file below. To use, first File > Open file
the binary of the program output by mbed compile
. Then Target > Connect
to the board, and Target > Program & Verify
Linux: Install the stlink package from the package manager if available or compile from source here.
To use, open stlink-gui and perform similar steps to the windows version to flash.
Alternatively, use st-info --probe
to search for programmers and st-flash write $binary_output_file 0x8000000
to flash.
About ham radio and how to get your license
Ever think about building your own radio? To talk to your friends across the county, the country, or around the globe? How about some astronauts on the ISS? Do you like the idea of bouncing radio waves off meteors or even the moon? Think you have what it takes to learn CW ("Morse code")? Amateur radio operators ("hams") do all this and more. By getting licensed with the FCC, you can join the ranks of 8 million radio amateurs in the U.S. Getting licensed allows you to:
Build and operate your own radio equipment
Transmit on radio frequencies (not channels) exclusive to radio amateurs
Transmit up to 1500W*
Experiment with new communication schemes
If you are enrolled in the decal, all of the following information should be provided to you in class or on piazza. There are three levels: technician, general, and extra. The steps for registering for a technician ham radio exam are as follows:
After selecting "individual" and "yes" to the first two questions, fill out all your information and submit.
Note that you will get your call sign after you have passed your exam.
How to solder/populate a PCB
Please note that there should be a through-hole and surface mount soldering workshop roughly every semester; ask on Discord for a date and time. It is highly recommended that you attend this workshop, as this page is more of a supplement than a stand-alone tutorial.
Now that you have a PCB, you are ready to solder. Make sure you have the following supplies:
Soldering iron
Solder
The board that needs soldering
Components to solder onto the board
Flux (either liquid in syringe or pen form)
Tweezers (for surface mount soldering)
Solder wick (not necessary, but useful)
Solder sucker (not necessary, but useful)
Voltage regulator/power input. Test with a multimeter (and by power LED).
Microcontroller. Test by writing a simple program to verify that you can use digital input/output pins. Can also verify by flashing a program that uses the debug UART port.
Sensors/actuators (one component at a time). Verify the component works by interfacing with the microcontroller. This may require having some code ready to communicate over I2C or SPI!
Remember to put away all tools you used when you are done. Keep whichever space you are working in clean.
Through-hole soldering steps (repeat these steps for each joint):
Place your circuit element into the PCB.
Melt a small blob of solder on the tip of the soldering iron. This is called “tinning the tip” and it improves the transfer of heat from your soldering iron to the component you want to solder. Make sure to do this to avoid oxidation and permanently ruining the tip.
If necessary, apply flux to the metal ring on your PCB. Flux is usually more important for surface mount soldering.
Touch the tip of your soldering iron to the metal ring and component leg (of a through-hole component) at the same time. (See diagram below)
Feed solder into the joint (not the soldering iron) while this is happening. It should only take a couple of seconds at most to fill the joint with a proper amount of solder.
After enough melted solder is present, stop feeding solder and remove the tip from the joint.
Clean the tip of the soldering iron by dabbing the tip on a wet sponge.
Let the joint cool down for at least 5 seconds and then trim the ends of the wire(s).
The following tutorial is for through-hole soldering:
Surface mount soldering is a bit more difficult. The components are small, and it's easy to short pads (the metal parts that you're soldering onto) and components together. But all it takes is practice!
The steps to do surface mount soldering is similar to through-hole:
Place your circuit element onto the PCB.
Tin the tip. Very important.
This is when it's good practice to use flux! Apply some to the pad before soldering. After you're done, put some flux on the solder blob and apply heat with the soldering iron to flatten peaks.
While soldering, touch the tip of your soldering iron to the metal pad and edge of the component leg at the same time.
Feed solder onto the pad (not the soldering iron) while this is happening. It should only take a couple of seconds at most to cover the component and pad with the right amount of solder.
After enough melted solder is present, stop feeding solder and remove the tip from the pad.
Clean the tip of the soldering iron by dabbing the tip on a wet sponge or brass sponge.
Let the joint cool down for at least 5 seconds and then refer to the flux step above.
The following tutorial is for surface mount soldering:
This is a slightly more professional way to solder boards. Faster, but with some risk
Reflow Oven: essentially a toaster over that can follow a pre-programmed temperature profile
Solder paste: similar to solder, but comes in a syringe and is paste-like. When heated past a certain temperature, solder paste flows, and upon cooling forms an ordinary solder joint.
The Chenming Hu Innovation Lab (Supernode) contains a reflow oven. STAR as a team has used it successfully to solder components. Here is how to do so:
PCB to be soldered henceforth referred to as the "target PCB"
PCB blanks, preferably large and of the same height as the target PCB
Stencil (usually ordered from OSH Park)
Solder paste (63/37 Sn-Pb)
We currently have a syringe labeled CalSTAR in the Supernode refrigerator
This is expensive, so try not to waste it
Masking or other tapes
Scraper / credit-card-sized card
Clean the target PCB with isopropyl alcohol (isopropanol)
Arrange spare PCB blanks in a configuration around the target PCB as follows:
Make sure the PCB to solder is snug and there are no gaps around it. If the blanks are thinner (e.g. 31 mils) than the PCB to solder (e.g. 61 mils) or vice versa, you can double-stack. It is important to have the blanks be at the same height as the target PCB
Next, position the stencil such that the holes in the stencil line up perfectly with their respective pads
Once alignment has been achieved--and be sure that it's as close to perfect as possible--tape one edge only of the stencil to the blanks and orient it so the taped side is away from you:
Squeeze solder paste from the syringe "above" (tape side) each section of pads
You will likely have to add more solder paste after the first pass. It is OK to recover solder paste, move it around, etc., but be very careful not to scrape too much side-to-side or away from you. The stencil must remain flat and in position
Continue spreading the solder paste around until each pad clearly has solder paste on it. We have found a steep angle allows for the collection of paste from the top of the stencil, while a low angle and higher amounts of downward force can help to get paste through the holes in the stencil
Gently lift the stencil from the board and flip it "up", exposing the board
Using tweezers, carefully place all components according to the reference designators/layout.
After placement, verify each component is securely on the board by gently pressing down on the top of the package with tweezers
Remove the board gently from the blanks, without tilting it overly
After placement, components should be somewhat attached to the board--the solder paste is sticky. All components should be aligned with their footprints.
It's finally time!
Before starting this section, open all windows in the vicinity of the oven. This process may produce unpleasant and carcinogenic odors.
Open the reflow oven and carefully set the board on the ceramic / kapton tape spacers. Do not place the board directly on the metal tray of the oven
Close the oven door
Turn the oven on with the switch on the back. You will have to walk around to the other side of the oven to access it
Select the pre-set reflow profile for 63/37 solder.
Start the heating sequence.
Even though the reflow oven will not quite be able to follow the profile specified, we have had no known problems with just letting it run--the temperatures reached are sufficient. Abort only if it is abundantly clear that the oven will not reach anywhere near the desired curve, and restart--if the oven starts from 50C, there should be no significant issues.
Allow the oven to cool, and carefully remove your newly-reflowed board after waiting a few minutes for it to cool down!
Inspect the board for any "tombstoning", shifted parts, failed connections, etc. Some amount of these are normal and can be reworked with the hot air rework station or soldering iron.
Inspect smaller connections under the microscope, and retouch if necessary with a soldering iron
Do not be alarmed if the board is slightly browned--it's been toasted, after all
How to use the lab equipment
The power source is used in place of a battery when running hardware tests. You can connect this to your circuit by using banana plugs, pictured below. By convention, red should be connected to the (+) terminals, and black to the (-), or ground, terminals.
As described by the gif above, follow these steps to set up the power supply:
Turn on the power supply by pressing the Power on/off button.
Set a current limit. To set a current limit, first push the "Display Limit" button. Next, push the "Voltage/Current" button on the right of the machine so that the current is selected (blinking). Then, use the arrow buttons on the right to select the digit you want to adjust, and then use the knob to adjust the value of that digit. Generally, we will use 0.100A unless otherwise noted. While 0.100A may seem small, it is still enough current to cause serious damage to the PCB you're testing.
Select an output: This device is capable of outputting 3 different voltages with maximum values of 6V, 25V, and −25V respectively. Make sure to push the button for the output you would like to use.
Set the voltage: After selecting the correct output (step 3), set the voltage to the desired value. To do this, push the "Voltage/Current" button so that the voltage (displayed on the left) is selected (blinking). Then adjust the value using the arrow buttons and knob, like when you set the current limit. Make sure you are adjusting voltage and NOT current.
Turn the output on: By default, the output of the device is turned off. For the device to actually output current, press the "Output On/Off" button. Always turn the output OFF whenever you are idle / don't need the Power Supply!
Note that these probes have the same connector as the oscilloscope probes. But beware! The function generator and oscilloscope probes have different impedances, which means if you use the wrong probe for the instrument you're using, your output will give you absurd voltage values.
Multimeters can come handheld or in the lab as shown above. They are used to measure the resistance, current, or voltage difference across two terminals. They can also be used to test for continuity. This means that you can determine what points are shorted together or not. You can use banana plugs with this machine, but the probes shown below are generally better to touch at specific points.
Follow these steps to set up:
Turn the multimeter on.
Connect the probe to the multimeter. You can determine what terminals to plug the probes into by looking at their labels.
To measure voltage or resistance or to test for continuity, plug the red probe into the terminal with the V, Ω, and diode symbol.
To measure current, plug the red probe into the terminal with the capital "i" next to it.
The black probe should be in the terminal labeled "LO" between them.
Touch the ends of each probe to the nodes on the board that you want to measure across/test continuity for. You can toggle the information you want to see on the multimeter by pressing the DC V (for DC voltage), AC V (for AC voltage), Ω (for resistance), or cont ))) (for continuity) buttons. When you press cont, it will say open until it is shorted. If there is continuity, it will beep.
The oscilloscope can be used to measure signals that change over time. Unlike a voltmeter, which only shows the instantaneous voltage value, the oscilloscope shows a graph of voltage versus time, which is useful to see how devices respond to inputs. This piece of equipment may look pretty complicated, but most of the knobs are to adjust axes. Oscilloscopes can also be used to simply measure DC voltages, as one would with a voltmeter.
The oscilloscope probe that connects to the color-coded metal terminals at the bottom looks like this:
Follow these steps to set up:
Turn the oscilloscope on (button at the bottom left corner).
Connect the probe to one of the 4 input channels (yellow, green, blue, or red). Make sure that the channel is on (indicated by a green light on the channel number). To turn a channel on (when it was originally off), simply press the corresponding numbered button. To turn it off, push the button again, and the light will be off.
Connect your probe to your circuit.
Auto Scale: Potentially skip steps 5-7 by using the "Auto Scale" button (see the image above) to automatically scale the axes. Don't get too dependent on the "Auto Scale" button; sometimes it doesn't do a "good enough" job.
Adjust the horizontal axis of the plot. The large knob at the top (immediately to the right of the screen) controls the horizontal time axis and allows you to zoom in or out. The time increments represented by the tick marks on the plot are indicated at the top of the screen.
Adjust the vertical scale. The larger of the two knobs for each channel (the one above the button with the channel number) allows the vertical scale of the voltage graph to be adjusted. As with the horizontal scale, the number of volts per tick mark on the graph is marked at the top of the screen.
Adjust the offset. In some cases, signals will appear off-screen; adjusting the smaller of the two knobs (below the channel number button) corresponding to each input will shift signals up or down on the plot.
Add measurements such as average voltage, amplitude, etc. Measurements can be added by pushing the "Meas" button and using the buttons below the screen to select and add measurements.
The function generator can be used to provide test inputs to your circuits. It acts like a power source, but there is a difference. While the power supply is capable of giving you a fixed voltage, the function generator can output sine waves, square waves, and a variety of other waveforms that change over time. Sometimes the function generator is useful if more independent DC supply voltages are needed than the power supply can provide.
Steps to set up the function generator:
Connect the function generator probe (pictured above) to either channel 1 or 2.
Press the "1" button for channel one and the "2" button for channel two to see their menus. Here, you can set the output load (for example, high Z), voltage limits, as well as turning the output on and off (as you would with a power source).
Press the button labeled "waveforms" to get a list of waveforms. Press the blue buttons on the bottom to select your desired waveform.
Press the "parameters" buttons to set the parameters of your waveform. Here you can use the keypad, knob, and arrows to adjust the frequency, amplitude, offset, duty cycle, and phase of your waveform. Again, use the blue buttons at the bottoms to toggle between parameters. You can also press "units" to change the units.
Professor Miki Lustig often teaches a Ham Radio decal, along with his class EE123: Digital Signal Processing. You can check for information.
Register on the FCC website to get an FRN (FCC Registration Number). You will need this for all future ham exams. Click , then click "Register and receive your FRN."
While you wait to get your FRN, you can search for exams in your area by clicking . Note that there will probably be one in Berkeley at least once a semester. is what you should bring.
There are many resources on the ARRL website to study for the exam, such as the . However, seems to be the best place to do (many) practice exams.
If you are at a soldering station, do NOT eat or drink there whether you're soldering or not. Ever. Here is what the CDC and WHO have to say about lead poisoning: ; .
When putting together your board, remember to test as you solder. This will make sure that you have a better idea of where a bug is if you run into one. This means soldering on a module and then testing that module before moving on to soldering another module. Refer to " on information relevant to testing. An example of how to break up soldering a board into modules is as follows:
There are many free through-hole components around , and you can just ask someone for surface mount components. It's important that you practice. Please ask for help if necessary.
Use a scraper or card to press firmly down on the stencil and spread solder paste, drawing the scraper toward you. At no point should you scrape away from yourself, lifting the stencil!
Straw rocketry is a simple activity involving construction of a simple paper rocket that can be launched with a straw. Students analyze the effect of different design parameters and environmental factors that affects launch distance. The activity takes about 30 minutes and is intended for an elementary school audience.
Slides: https://docs.google.com/presentation/d/1Vif695uiCu6y9bhEMQwTcH22k6azwuCwQ9YsuHmS5MY/edit?usp=sharing
Lesson Plan: https://drive.google.com/file/d/1vyKGsn_8eoh4g4PlnNFBl6_rF8-BKQJL/view?usp=sharing
Templates: https://drive.google.com/file/d/1OvNhKaebrr6VughCz8dqnWIUvN_DHquf/view?usp=sharing
Alternatives to LiPo (Lithium Polymer) batteries that are suitable for high temperatures.
The maximum recommended/tested temperature for LiPo batteries is 60C [1].
When LiPo batteries operate at high temperatures, they are at risk of severe performance degradation, and produce gasses such as O2, CO2 and CO. This is because of the interactions at the electrolyte-electrode interface [1].
This has caused significant distress to our team, as we compete in New Mexico which routinely experiences extremely high temperatures.
Batteries better suited to high temperatures will have different internal chemistries that have high thermal stability. This is not a new problem and more suitable batteries do exist. A few have been listed here. More information will be added if we find reliable suppliers for these batteries and can try to work with them ourselves.
References
A walkthrough of our component selection process for designing boards.
One of the challenges of circuit design is narrowing down exactly which components you want to use. For example, suppose you need to include a zener diode as part of your circut. A quick internet search on supplier websites reveals more than 70,000 possible options! How are you supposed to narrow it down?
This option is relatively simple but works very well: browse through some of our old electronics projects and re-use components that we've used before. For example, if you need a zener diode, check our past projects to see if any of them incorporated a zener diode, and re-use that specific diode for your current project (as long as that diode meets your current project requirements). Some of the projects that you can browse are:
Open up kicad and browse through their schematic symbol libraries. In these "Kicad default libraries" you can find a whole host of specific part numbers for each general type of component (amplifiers, transistors, etc). There are two main advantages to using components from the Kicad default libraries: first, obviously, you'll have easy access to the symbol and footprint for your part, without having to make them yourself or search online. Second, by virtue of the component being included in Kicad's deafult libraries, you'll know that it's a very popular component.
If we go back to our old example of trying to find a zener diode, here's how we can search the Kicad default libraries. First, open up the schematic editor and select the button to add a component:
Then, type "zener diode" in the search bar:
Most of the options it shows us here at the top are 'generic symbols' and aren't specific part numbers.
If we scroll down, now we can see some specific part numbers. For example, here I've selected the BZV55B2V4 zener diode, and if we later decide we want to use it in our project, we can buy that specific diode from digikey.
Sometimes, if a component isn't available in the Kicad default libraries, you can find it in an online Kicad library, which you can download and incorporate into your project just like a component from a default library. One of the best resources for finding these online kicad libraries is snapeda.com. This website allows your to search by part type (or by specific part number) to get symbols and footprints that you can integrate into your kicad project.
If you go to the main page and type "zener diode" then the search results will look something like this:
One of the great things about SnapEDA is that it tells you how popular each part is by displaying the number of times that each symbol and footprint has been downloaded. If something has over 100 downloads, that usually means its a very solid choice. For this reason, looking up parts on SnapEDA is still useful even if you already have the symbols and footprints. If you're trying to choose between two zener diodes, and one of them has much more downloads on SnapEDA than the other, then that might help to inform your choice between them.
Digikey.com is the main website that we use to search for and purchase parts. However, we frequently buy parts from other sources as well--mouser.com is a good example, offering almost all of the same features as digikey. We also buy parts from Amazon sometimes, like the ESP32s used in the LE2 ground system.
For now, though, you can stick to digikey, as that will make things simpler. Continuing with our zener diode example, you can start by typing 'zener diode' into the search bar at the top of the screen. Doing so will lead you to a page that looks like this, where you can select the category of components to browse:
Click on "Diodes - Zener - Single." Next, you'll see a page that looks like this, where you can browse all the specific components to purchase:
You can start narrowing things down by selecting some filters. Under "product status", select "active"--this is one filter that you can always select right off the bat. After that, scroll through the rest of the filters and select the ones that apply to your project. For example, maybe you know that you'll need a zener voltage of 12V exactly--in that case, you can go to the "Voltage - Zener (Nom)" filter and select 12. Additionally, maybe the project requirements stipulate that the zener diode needs to support 500 mW of power; in that case, you can go to the "Power - Max" filter and select every power level above 500 mW. Oftentimes, you can also go to the "Mounting Type" filter and select "surface mount" because we usually use surface-mount components on PCBs due to their small size. (Though sometimes we do need to use through-hole components, usually when the components have some kind of high-voltage or high-current function).
Press the red "apply all" button after selecting your filters. This drops the number of results down to about 617. Next, unless you have a specific part number in mind, go to the "Quantity Available" tab and press the down arrow button to sort in descenging order or quantity available. This is done for two reasons; first, the parts with a very high number available are generally the most popular, and therefore the best to use. Second, we have had some problems in the past with parts that are out of stock on digikey (for example: we designed CAS in 2020 and included a component called the BNO055. That component ended up going out of stock, and as of 2023, it's still out of stock. Depending on how far in the future you're reading this, it may still be out of stock today!).
From here, you can scroll down the list of most popular components and note down any that look appealing. Note that, when digikey reports the quantity of a component, they include both the quantity that they have "in stock" (the normal way to buy them) as well as the quantity available on the "marketplace." The marketplace is relatively new so STAR doesn't have much experience buying from there. If you find a component you really like that's only available on the marketplace, by all means go ahead and buy it, but if you want to stay on the safe side, then stick to the components that are listed as "in stock" on digikey. At this point, you'll probably be able to get a shortlist of several components (10 or so) and start deciding between them.
Look at options from a reliable vendor. Some vendors that make lots of good components include Texas Instruments, Onsemi, Diodes Incorporated, Analog Devices, and NXP. Note that digikey allows you to filter by vendor when you are doing the filtering step.
If you are deciding between a few components, read their datasheets. Some datasheets have detailed pinouts, application circuits, debugging information, and more, whereas some other datasheets only have the absolute bare minimum. Components with more comprehensive datasheets are generally a better choice because they'll be easy to use.
Solderability is very important! Components with "little legs" (there's an official package name but I can't remember it) are much preferred because the metal part sticking out makes it relatively easy to solder. In contrast, some components have all their pads directly under the package without any legs at all. This makes it much more difficult to solder, although it can still be done by STAR's capabilities if there are no other options.
Go to adafruit.com if you're interested in getting breakout boards specifically. Adafruit has a much narrower scope than most other component distributors, and they tend to specialize in things that you can connect to an arduino or esp32, such as sensors and actuators. Adafruit usually has very extensive documentation and tutorials for using their components, which makes them a really appealing choice.
Some components are used a lot by STAR simply because our club used them before many times, so they should be prioritized when doing components searches. Some examples of this include the STM32F401RE microcontrollers, which was used in many projects (most notably CAS), as well as the ESP32 devkit-C V4, which was used for ELLIE and LE2 electronics.
If there's one component that is mostly really good but won't work for some reason (maybe its out of stock, or it doesn't meet the required power rating, or something else), try looking for a closely related component. Most manufacturers use a sort of naming convention in which components have more similar part numbers if they are more closely related. Many datasheets will even have an "ordering information" section near the end where they tell you the exact meaning of the naming convention for that family of components.
If the component you're looking for is something that a microcontroller communicates with, you should prioritize components that already have drivers written for them (available online), so you don't have to write drivers yourself.
You can literally just google something like "best zener diode" and see what the top few results are. This isn't the most effective strategy, but sometimes it can work.
A quick activity designed for Scientific Adventures for Girls. Elementary schoolers learn how to fold paper airplanes and various techniques to fold airplanes with different properties. The paper airplanes are modified with paper clips and hot glue to be compatible with the launchers. The launchers are laser cut from 1/4" plywood and 2 rubber bands tied in series.
You can click on each individual part to see more details about its symbol and footprint. Note that not all components will have both a symbol and footprint provided--some have only a symbol, some have only a footprint, and some have neither. Components with the will have a symbol, and components with the will have a footprint. If you get a component with only a symbol, it is possible to make the footprint yourself and incorporate both into your project (and vice versa). However, note that symbols are generally much easier to make yourself than footprints.
Basic paper airplane designs:
File for the launcher handle:
For laser cutting in a hurry, try the Quick Cut or Quicker Cut versions. Quick cut: Quicker cut:
Battery Type
Max Temperature
Potential Suppliers
Lithium Iron Phosphate (LiFePO)
200C [1], [2]
batteriesinaflash.com
Lithium Thionyl Chloride (LiSoCl2)
95C - 125C [3], [4]
Tadiran Eagle Picher
Jauch
Amazon?
Spacecraft Structures involves designing an engine mount analogue that is tested using a lever and a dummy weight shaped like a rocket to mimic the forces of a rocket launch. The objective is to design and build a structure that can withstand 3 launches using minimal materials. The entire workshop takes around 2 hours and has been run at Splash, Expanding Your Horizons, and SWE High School Engineering Program.
The structure itself is composed of two 1/4" plywood plates with enough space in between to fit a film canister, which represents the rocket engine. Coffee stir sticks and hot glue are the only other materials provided to construct the rest of the structure.
The structures are tested by placing them in between the rocket and the lever and dropping a 15 lb (6.8 kg) weight on the other side of the lever from shoulder height.
Current slide deck: https://docs.google.com/presentation/d/1Tvh4uL7LV4K578TAZ41O1hmjDH1xtWBw7VfJ3QOH_RE/edit?usp=sharing
Short version slide deck: https://docs.google.com/presentation/d/1qYkuULqG4q63alXvwlvJgF1JBPIipl0p_xpdBJXMaAc/edit?usp=sharing
Vector file for laser-cutting top and bottom plywood plates: https://drive.google.com/file/d/1LmVELYuEPEu2I09916-3BJlAm2x18kNZ/view?usp=sharing
Follow English conventions unless told otherwise
Leave names of existing places/companies/objects as is
ex. AT&T
Use the spellings/names of objects common in the US as opposed to those common internationally
ex. Labor vs Labour
Do not put a period after units unless other conventions dictate it
in, not in. or inches
3 ft, not 3'
30 mi/hr, not mph
4 hrs, not 4 hr
Nosecone is one word; not "nose cone"
Do not abbreviate words with symbols
ex. &, @
Capitalize proper nouns, but not regular ones.
ex. Nomex and Lexan, polycarbonate, payload, ejection subsystem
Replace words like 'Payload, Ejection, Movement' with phrases like 'payload system, ejection subsystem, movement subsystem' respectively.
Convention is to not hyphenate between latin prefixes.
ex. subteam is correct vs sub-team
ex. subsystem is correct vs sub-system
A sentence that uses a listing system within it should:
have a colon before the listing begins;
have semicolons between parts, and;
use the ", and;" transition before the last item.
Use --- in LaTeX to get the long m-dash used to separate parts of sentences. -More from brunston
Alka Seltzer Rockets are film canisters with 3D printed nose cones and fins, powered by Alka Seltzer tablets and water. Alka Seltzer is composed of sodium bicarbonate, citric acid, and acetylsalicylic acid (aspirin), which react when dissolved in water, creating carbon dioxide gas. This activity is designed for booths at Discovery Days.
For optimal results, add 3/4 of an alka seltzer tablet broken up into 4-5 pieces and add enough water to fill up the canister about 1/4 of the way.
Folder with nose cone and fin STL: https://drive.google.com/drive/folders/1hvyhlRqM5Wcn5oEIB2c1gB9fgIuNTpOw?usp=sharing
We developed a coding workshop for Rainstorm Summer 2020 to teach high-schoolers about algorithms in a 25 minute session through zoom. This activity is designed for students with no previous experience with programming.
There are 3 variations to this activity: elementary school level for Scientific Adventures for Girls, high school level (25 minutes) for Rainstorm, and high school level (55 minutes) for Splash @ Berkeley.
Original agenda:
Python file:
Original slide deck:
It's pronounced "LAH-tech" or "LAY-tech", not "LAY-tecks"; the letters in TeX are meant to represent the Greek letters tau, epsilon, and chi.
is a typesetting system, much like Microsoft Word or Adobe InDesign. It is not a text editor. is used widely in the scientific and technical publishing industry; if you've seen a document that looks like the picture below, chances are it was written in .
While documents come in all sorts of flavors, they generally share a similar appearance because they use the Computer Modern typeface. However, all the fonts, colors, layouts and pretty much everything is customizable--is a way of "programming documents".
While Microsoft Word is a "What You See Is What You Get" (WYSIWYG) system, is decidedly not. Instead, is written as code (see below), and then compiled, usually into a PDF.
The most common reason to use is because you are writing a document with equations in it. There is simply no other way to get beautifully formatted equations (although many programs like Word now support syntax).
Even if you don't have equations, allows writers to stop worrying about annoying formatting issues, breaking their document when they add a picture, etc. and focus on the actual content. Documents like reports and books can be written in sections and seamlessly re-compiled using the article
andbook
classes, while the formatting and numbering of tables, figures, references, citations, footnotes, etc. are taken care of completely automatically.
To give one example, if you have 5 figures labeled Fig. 1 through Fig. 5, you can insert a figure between Fig. 1 and Fig 2. and not have to worry about changing the references to Figs. 2-5 to Figs. 3-6. This can save an enormous amount of time when writing longer documents.
There are two ways to use : locally on your computer or in the *cloud*.
This is really for hardcore users and people without internet. You'll first need to install a version of compatible with your operating system. Head over to https://www.latex-project.org/get/ to get started; we recommed TeX Live for Linux, MacTeX for macOS, and MiKTeX for Windows. These downloads can be pretty big!
As mentioned previously, is a typesetting system, not an editor. You can write documents in Atom, Sublime, Notepad, Notepad++, vim, Emacs, ex, TextEdit, or whatever text editor you can get your hands on. That being said, TeXnicCenter and TeXstudio are popular editors for Windows, and MacTeX includes TeXShop; you might want to use these or similar TeX-oriented editors to edit your documents unless you know what you're doing. Linux users can choose from 10s of options; for some reason people who are into Linux are also into TeX.
Welcome to the future. Simply head over to https://www.overleaf.com/ (now merged with ShareLaTeX) to get started! UC Berkeley provides free Overleaf Professional with a verified berkeley.edu email address. Overleaf has hundreds of great templates and tutorials to help you get started.
While there are hundreds of tutorials on the internet, this one is pretty good: https://www.overleaf.com/learn/latex/Learn_LaTeX_in_30_minutes. When in doubt, just Google! Chances are someone's had the same question and made a StackOverflow post about it.
We have previously used to compile our reports for NASA Student Launch. If you ever need to make a checklist, design document, or report, feel free to use . Generally, Google Docs is a little easier for the uninitiated, but don't be afraid to make your documents look nice!
An intro to RPA: how/what to download, important components, etc.
This YouTube video covers the basics of using the Rocket Propulsion Analysis(RPA) Software. This doesn't cover how to model the thrust chamber for the intro project, but it will help you become more familiar with the program: https://www.youtube.com/watch?v=F3W3zZj4zX4
NOTE: This YouTube video uses the RPA Lite version. In order to model the thrust chamber you must download the RPA Standard Edition Trial Version. (The C++ one is not needed)
Trial version of RPA Standard Edition v.2.3.2 has the following functional limitations:
The user may run the analysis 3 times without restarting the software. To continue with evaluation, the application has to be restarted.
RPA downloads can be found here: http://propulsion-analysis.com/RPA/download.htm
Complete User Manual(v2.3): Rocket Propulsion Analysis - User Manual (rocket-propulsion.com)
Engine Definition:
define the parameters for the combustion chamber and nozzle sizing
Nominal thrust, nominal mass flow rate, or throat diameter must be specified
switching on the flag for performing the thrust chamber thermal analysis
specify additional heat transfer and chamber cooling parameters on the screens Heat Transfer Parameters and Thrust Chamber Cooling.
Can define the type of engine feed system
parameters for cycle analysis can be specified on the screen Propellant Feed System
Propellant Specification:
Define propellant type(s) and mixture ratio. The mixture ratio can be specified either as an O/F ratio (ratio of "oxidizer flow rate" to "fuel flow rate"), or as an oxidizer excess coefficient, given as ratio of desired O/F to stoichiometric O/F.
Click Add Oxidizer/Fuel. You can filter the list in the dialog window, using a regular expression(ex “oxygen”). The filter pattern is applied to both columns of the table.
Nozzle Flow Model:
Nozzle Conditions: If you are solving the nozzle flow problem, you have to define at least nozzle exit conditions, specifying one of three parameters: nozzle exit pressure, nozzle expansion area ratio, or nozzle expansion pressure ratio.
The feed system can be thought of as a combination of all of the valves, tanks, and pipes in the rocket. The main purpose of this system is to move propellants from tanks to the injector at a specified pressure and flow rate.
As the feed system is composed of pipes, valves, fittings, and tanks, these components greatly affect the operation of the feed system. The pressure and flow rate of the propellants that the feed system is able to deliver to the injector also influences injector and thrust chamber design, as the thrust chamber pressure and injector pressure drop combined must be less than or equal to the feed system pressure delivered before the injector. The feed system must also interface with some external structure to hold it in place during ground testing or flight while integrated into a rocket.
As is obvious from the above document(RPE Chapter 6), there are many choices for feed system types. For our purposes, a turbopump system is not viable because of its complexity. Under pressurized systems, a flexible bag within the tank and piston pressurization system are also too complex for a college rocketry team to do. Then, the remaining choices that are not too complex for a college rocketry team are Pressurized systems> Direct gas pressurization> By stored inert gas> As received> Regulated pressure & Blowdown. These are the two viable choices for our team that will be further examined below
In this case, gas from a high pressure gas supply tank is flown through a regulator, resulting in a near constant pressure of gas to the propellant tanks. This results in a near constant pressure at the thrust chamber, in turn causing a near constant thrust. The propellants in the system can also be regulated instead by flowing the propellants through a regulator. This choice results in a simpler design for the thrust chamber than in a blowdown system, as it is easier to design a thrust chamber for propellant at a constant pressure than to design a thrust chamber that receives propellant at variable pressures.
A blowdown feed system works instead by storing the highly pressurized gas inside the fuel and oxidizer tanks instead of inside a different tank. As the gas and propellant is in the same tank, they both are at the same pressure. When the valve below the tank is opened, the propellant in each tank can then start flowing to the engine. This figure shows two engines, but the concept is the same with one engine as well. As more fuel is expelled out of the engine, more pressure is lost in the tanks, resulting in a lower pressure of the propellants over the firing time of the engine.
Rocket Propulsion Elements Chapter 6: Liquid Propellant Rocket Engine Fundamentals
Pipes and Fittings
Valve Types
Valve Actuation Methods
Fuel Choices
Oxidizer Choices
E-matches, starters, igniters, initiators and the like
Generally, there are two classes of ignition devices in high power rocketry (HPR): igniters/starters, and e-matches. The former are used to start Ammonium Perchorate Composite Propellant (APCP) motors from a 12-volt supply on the ground, while the latter can be used to start smaller black powder motors on the ground, parachute ejection charges in-flight, and second-stage motors in-flight.
From the Apogee website:
E-matches - While these are regulated by the government and require a Low Explosives User Permit (LEUP) to purchase, you can make your own from a kit without a permit. Order the Starter Chipboards and some special igniter dip designed for low-current igniters. We also have (as of November 2018) an ATF approved non-regulated e-match called the Firewire Initiator and the Firewire Mini that does not require a LEUP! This would be the primary choice if you didn't want to dip your own Starter Chipboards.
This part usually contains a nichrome wire that heats up when current is passed through them.
This is the part that burns. Apogee sells the H-3 Compound E-match Dip for making e-matches (low-current, low-voltage, to ignite black powder usually) and QuickDip Pyrogen for longer-burning starters (starting APCP motors on the ground or in the air with high current).
General description of injectors, types of injectors, and injector manufacturing.
Injectors are needed to spray the bipropellants (i.e. fuel and oxidizer) into the combustion chamber in a way that controls the atomization, combustion rate, and combustion efficiency of a liquid engine. Injectors are a vital component of a liquid rocket engine that will affect how efficiently the energy of fuel is converted into the needed thrust for a rocket. There are a variety of injectors to choose from. When designing an injector, some factors to consider are the bipropellants used, engine application, viability, etc.
A pintle injector consists of two concentric tubes and a pintle. The cylindrical tubes are responsible for carrying the propellants to the combustion chamber. Generally fuel will go through the inner tube while oxidizer goes through the outer tube. The pintle is a protrusion at the end, which allows the fuel carried on the inner tube to deflect at a certain angle. The fuels will meet and mix at the impinging point and proceed to combust. By varying the size of the annular and center gaps that the fuel passes through, this allows for throttling of the engine and controlling of the flow into the combustion chamber.
A properly implemented pintle injector can achieve combustion efficiency adequate for liquid engines (96-99%). The design is relatively simple and has proven dependability. Performance can be easily optimized by varying the gap sizes. It works in engines that have to be restarted. Overall, this injector is a simple, adjustable, and high performance option.
Pintle injectors only work well for liquid and gelled propellants. Thermal stress is more concentrated in the certain parts of the combustion chamber which can lead to burn through. Another disadvantage is that there are no correlations for level of mixing and spray size.
Similar to an actual showerhead, the propellants are fed in a straight path into the combustion chamber where they will then atomize and combust. The propellants are sprayed through holes that would maximize atomization.
This is the simplest option being relatively easy to make and implement such as by repurposing a commercial showerhead and integrating it into the engine plumbing.
Mixing is dependent on the turbulence of the propellants entering the combustion chamber. Otherwise, the propellants will go straight in and have poor mixing. In general, the combustion efficiency of a showerhead injector will be low compared to other options making it viable for experimental, non flying engines.
Propellants are fed into the combustion chamber at certain angles. To achieve this, many holes are drilled into the face of the combustion chamber. The fuel and oxidizer manifolds can be spaced in different orientations to vary where and how much mixing occurs. Some stream patterns include doublet, triplet, and self-impinging stream patterns.
If done correctly, this can achieve strong combustion efficiency and is scalable depending on the size of the combustion chamber.
This design can be quite complicated to drill sets of holes correctly accounting for entry angles, fluid velocity, and mass flow rate. Atomization efficiency decreases at high entry velocities because droplets will scatter in different directions. The degree of precision and equipment needed for this to be viable is most likely beyond the budget of the club unless a cheaper solution is found.
As suggested by the name, coaxial swirl injectors consist of coaxial tubes that will feed the bipropellant into a mixing chamber through tangential inlet ports. The oxidizer flows into a swirling chamber at an angle such that it will swirl and then spray out into the combustion chamber to thoroughly atomize. The fuel is fed directly into the combustion chamber where it will atomize with the oxidizer.
In theory, can achieve the highest combustion efficiency and thus the highest performance. The spray pattern is similar to a pintle injector but without the need for a pintle to deflect the fuel due to its angular momentum.
The variables involved in swirling such as the speed and the angle at which the swirling oxidizer is injected can be more difficult to optimize for this injector.
The bread and butter of the propulsion system
NPT stands for National Pipe Thread (and sometimes National Pipe Thread Taper). It is a common type of thread used on plumbing. If you see a threaded fitting or pipe around your house, it most likely uses an NPT thread. The most significant thing to know about NPT threads is that you need to use Polytetrafluoroethylene (PTFE) tape on the threads to ensure a leak-free seal! This tape is also commonly referred to as "Teflon tape". YOU MUST USE THIS TAPE! Generally one or two clean wraps around the threads is enough. To be safe, take off old Teflon tape and replace it if you think it's insufficient.
You must use Teflon tape on NPT Threads!
Some other points about NPT threads:
NPTF is a variant of NPT with a slightly different major diameter. They are cross-compatible with NPT threads, but some care has to be taken and you should always use teflon tape! We generally don't use them, but be aware when buying components. NPTF does NOT mean NPT Female.
NPT threads have a taper of 1 inch per 16 inches. Male threads are tapered in, and female threads are tapered out. This is to ensure a better seal.
Where we use NPT threads:
Black flexible tubing to UFA (Universal Fill Adapter, see below) connection
Most N2 (Nitrogen gas) fittings
Non-Swagelok® 2-way ball valves
Other large pipe threads (i.e. N2 cylinders, etc.)
Further Reading:
Swagelok® is a company which manufactures tube fittings and various other components. Swagelok® tube fittings are proprietary and only work with other Swagelok® tube fittings. These fittings offer several benefits over NPT, including:
They do not require PTFE (teflon) tape
The are good for high pressure
They are vibration resistant
They can be assembled easily
They're easy to use on plain tubing
The first time a Swagelok® fitting is used on a pipe end, it must be properly prepared. This preparation process ensures that the ferrule (the conical frustum-shaped metal bit) is properly seated into the tube. The video linked below provides a good explanation of how to do this.
Video demonstration: https://www.youtube.com/watch?v=jB_Nyje_HNE
NPS stands for National Pipe Straight. It is the same as NPT but without the taper. It is NOT compatible with NPT. We do not use it at this time.
Ball valves control the flow of the working fluid. We currently have:
2-way ball valves with NPT threads
3-way ball valves with Swagelok® fittings
These valves have the inlet positioned in the middle of the T. The valve can either be closed (when the handle is upright), or opened to either side by turning the handle arrow to that side.
Ball valves are fairly straight-forward, but it is important to double check in procedures that the interior "ball" space in the valve is not pressurized after disassembly. For safety, don't put fingers around the openings when opening ball valves.
A check valve is a one-way valve that lets flow in one direction but not in the other. There is typically an arrow on the component indicating the direction of flow. We use both Swagelok® and NPT check valves.
It is critical that check valves be inspected to ensure that they are mounted in the right direction.
A pressure regulator is a device that reduces the inlet pressure down to a specified output pressure. They are used for both gases and liquids. We have several regulators in our propulsion system:
The regulator on the big N2 cylinders
1800 psi regulators on the N2 Composite Overwrap Pressure Vessels (COPV's)
Adjustable Swagelok® regulators for use with either N2 feed pressure or liquid pressure regulation
These regulators have a high and low pressure port marked "HP" and "LP". They must be properly aligned!
These regulators do NOT work at cryogenic temperatures
It is normal to hear a loud buzzing when turning these regulators from closed to open under pressure. This is due to the internal diaphragm vibrating, and is perfectly normal.
Regulators have a high pressure (HP) and low pressure (LP) side. Make sure these are aligned properly.
A Universal Fill Adapter (UFA) is the black knob assembly connected to the end of the black, flexible tubing. It attaches to paintball COPV N2 tanks and allows us to open or close the valve on the tank. It works by using the knob screw to push down on a spring-loaded ball, which allows N2 to flow out of the tank.
Some of these have an issue where the knob is very badly fixed with illegitimate Loctite. We prefer using the set screw-type knobs, particularly those manufactured by Ninja.
The remote line is the assembly of the UFA with the black flexible tubing.
Pressure gauges measure gauge pressure of the fluid (as opposed to absolute pressure). They are typically used with a T-joint. Our pressure gauges are (theoretically) not cryo-rated.
A quick disconnect is a type of fitting which allows a quick connection/disconnection (hence the name), without any threading. We use these on our mobile filler. They are less secure than other connections, so they should only be used where necessary.
To connect a quick disconnect:
Pull back on the outer ring on the female end
Insert the male end (AKA nipple) into the female end
Release the outer ring until it snaps back and you hear an audible click
The two halves should now be connected and you should not be able to pull them apart without pulling back the ring
If you can pull them apart, simply try again. You may have to wiggle the quick disconnect a little to get the outer ring to snap into place properly.
To disconnect a quick disconnect
Pull back on the outer ring on the female end
Separate the two halves
Release the outer ring
Always make sure Quick Disconnects are are properly connected! They are tricky and can lead to serious safety issues if they're not properly connected.
We buy relief valves from Swagelok®. These valves work using a calibrated spring, which under a certain pressure, will allow fluid to flow through the valve. We use these as safety devices, to ensure a safe depressurization in the case of over-pressurization. It is important that the these vents be kept clear of personnel and high-pressure tanks at all times when the system is pressurized.
Never adjust a fitting on a high-pressure system. If you don't know whether a section of tubing or tank is pressurized, depressurize it first.
Always check all fittings for tightness before pressurizing any system.
Deciding which parachutes to use: where to buy them from, how big, and other things to consider
For parachute purchasing, Recovery typically sources from FruityChutes. They also provide us with a 10% discount if you mention that you are with STAR. Their chutes have a coefficient of drag (CD) of 2.2 for large iris or 1.9 for smaller iris parachutes used for drogues which is ideal, we would not want that to significantly decrease.
This is the order of recovery. Note the order of deployment and location.
The purpose of the drogue parachute is to slow down the rocket such that once at terminal velocity we can safely deploy the main parachute. It is deployed at apogee. The drogue parachute should be significantly smaller than the main parachute so as not to exacerbate wind drift. With respect to mounting in the rocket, the drogue is typically attached the the lower portion of the rocket (nose cone side).
The purpose of the main parachute is to significantly slow down the rocket to allow it to land safely and softly. This is to preserve the rocket and materials within it. The main parachute is deployed after the rocket with the drogue parachute has reached terminal velocity. Recently, deployment has been within a range of 700-800 feet of elevation. It should be significantly larger than the drogue parachute. With respect to mounting in the rocket, the main parachute is typically attached to the upper portion of the rocket (booster side).
Our goal in parachute sizing is to reasonably minimize ground hit velocity, the kinetic energy at landing, and drift of the rocket.
We use Open Rocket as our main calculator for kinetic energy, drift, and ground hit velocity. You should also be sure that there is not an issue with the jerk moment, which would occur if there is too much of a difference in size between the drogue and main chutes. If there is an issue, it will be easily identified in Open Rocket.
We typically try to minimize the ground hit velocity. According to IREC regulations: ground impact speed should be no more than 30 ft/s or 9 m/s.
We typically try to minimize the kinetic energy of sections. According to our STAR regulations: maximum section Kinetic Energy should be no more than 100 Joules . This is for the purpose of safety and to ensure delicate components are not broken upon landing .
The upper section, avionics bay, and lower section should all meet this requirement.
where m is the mass per section, v is the terminal velocity post main chute deployment.
We typically try to minimize the wind drift. According to IREC regulations: main deployment should not exacerbate wind drift (eg 75 - 150 ft/s or 23-46 m/s). Furthermore, we have additional STAR specific regulations: drift should be within the confines of launch site, drift should be less than ⅖ of apogee.
Wind drift should be calculated for 10 mph wind = 4.47 m/s
Open Rocket will give results of expected drift based on inputs of weight of the rocket, apogee height, parachute sizes, and wind conditions. Or calculations can be made from the expected flight time.
Where v is wind speed (4.47 m/s) and t is expected flight time.
Commercial off-shelf altimeters are often required and just nice to have for redundancy. We use the 2 perfectflite stratologger in the avionics bay for main and drogue parachute deployment.
For the most part, the altimeters do not need to be programmed once bought. It can be reprogrammed for different modes including ignoring the first X seconds of flight. Refer to the manual linked at the bottom of this page but the reprogramming wires are purchased and housed in the Etcheverry locker.
Positive and negative does not matter for main and drogue as both sides go to an E-match. Same with switch, both sides are the same. However, make sure that the positive and negative sides of the battery is connected properly and listen to beeps for accuracy.
Manual: http://www.perfectflite.com/Downloads/StratoLoggerCF%20manual.pdf
Updates to the avionics sled to improve ease-of-use during launch.
The avionics sled fits into the avionics bay tube of the rocket. The sled must hold two altimeters and two 9V batteries. On the day of launch, altimeters need to be wired twice - first for ground test and then for the main flight. In order to be time-efficient, it is important that the altimeters can be easily accessed.
The AirBears avionics sled was the same as that used for Arktos. It fit into a 4" rocket and was used for the test launch on Nov 16, 2019. Overall, the design was effective as all components were housed and both parachutes successfully deployed. However, there was difficulty in wiring the altimeters due to their placement along the raised edges where the sled slides into the avionics bay.
The goals of the redesign of the avionics sled for the IREC 2020 rocket were the following:
Optimize the avionics bay for a 6" rocket
Address wiring concerns from AirBears to improve ease-of-use during launch
The new chosen design was an I-beam model, in which the batteries were placed in a center section of the sled and one altimeter was mounted to each side, as shown below. This design somewhat improved the space usage in the vertical direction, but there was significant unused horizontal space. The Recovery subteam selected this design because they felt it was more important to be able to wire the altimeters efficiently at launch than to use the least possible space.
The goals for the avionics bay designs for the 2022 Stage Separation vehicle were as follows:
Integrate sufficient room in at least one avionics bay to accommodate the Common Avionics Stack (CAS).
Integrate sufficient room to accommodate off-the-shelf altimeters in addition to CAS, to allow for flights without CAS integration and also ensure failsafes for early CAS test launches.
Include multiple avionics bays, as the two-stage nature of the SSEP vehicle requires at least one for each stage.
In the end, the SSEP vehicle incorporated three different avionics bay designs:
An upper stage avionics sled used to manage recovery of the upper stage. Its overall structure similar to the IREC 2020 design, but with an additional hole to accommodate CAS. This design placed CAS in its own "hole" in the bottom while the altimeters and batteries were secured to a central "wall".
An interstage avionics bay used to ignite the upper stage motor after stage separation. Its structure is different compared to the other ones; because of the limited space available in the interstage, it is not CAS-compatible. It has similar top and bottom pieces that neatly slide into each other, and are held closed by the bulkheads and spacers.
A lower stage avionics bay used to manage recovery of the lower stage. It is somewhat different from the IREC 2020 design but maintains the same basic structure, with a sled sliding out of two rings, which in this case are connected with an overall housing. Similar to the upper stage avionics bay, it places CAS in its own "level" while the other altimeters are kept on the second level.
FEA simulations involve the numerical solving of partial differential equations that rule our known world. The simulation software takes in a geometry and then creates a mesh out of it. A mesh is your geometry broken into a large, but finite number of elements. Each of these elements, whether they be cubes, tetrahedrons, pyramids, etc. can then have a PDE applied over it. The specific PDE applied depends on the type of simulation you are running. For instance, for an electric simulation Maxwell’s equations will be applied, and for thermal simulations the heat equation will be applied. Once your geometry is separated into a number of finite elements, you can then apply boundary conditions to the entire geometry. These boundary conditions include but are not limited to an applied force, an applied pressure, heat applied, and a voltage. The software then takes the boundary conditions coupled with your mesh and continuity equations in order to produce the results you are asking for. These results could be deformation, stress, strain, resultant force, etc. The main softwares you will use to complete simulations are FEA within Solidworks, ANSYS’ FEA simulations, COMSOL, and/or simscale. We highly recommend ANSYS as it is highly accurate and we have access to free licenses.
To begin using Ansys, open the Workbench application. Select the static structural icon on the left menu to begin working on a static structural project. The project window will contain several items that you must fulfill in order to run the simulation.
Engineering Data
The Engineering Data item is where you select the material that the component is made out of. You can choose from an extensive list of preloaded materials that Ansys offers, or you can create your own material with its own properties. This might be helpful for asymmetric materials or extremely unique materials, but we will generally be able to get good results from preloaded materials.
Geometry
The Geometry item is where you will be importing or creating the 3D part you will be running the analysis on. While it is possible to create the part in Ansys, we strongly recommend using SolidWorks or some other 3D modeling software to create and save the part, and then import that part into Ansys. To do this, simply select Import Geometry, and Browse to look for the file.
Model
Selecting Model will bring you to a new window (after a significant loading period) where you will be completing the rest of the items. Here, you will be assigning the material to the body, creating the mesh, and specifying the conditions and settings of the FEA.
To assign a material, click on Materials in the directory on the left of the window, and insert your material with Material Assignment. Then, select the whole body, reselect Material Assignment, and click apply
You can select different things on the body, like surfaces, vertexes, etc. using the boxes above the model window
Now we must create the mesh. This is creating the finite elements in the finite element analysis. To start, you can simply click on the Mesh tab and generate mesh to see what Ansys will give you. Usually, we want a more fine mesh for more accurate results. To do that, select mesh, go to insert, and select sizing. From there, you will select the geometry just as you did for material assignment. You will now be able to customize the mesh size once you select generate mesh! A word of caution, too fine of a mesh will cause very long loading times, so don’t go crazy.
Next, we must assign boundary conditions. To do this, go into Static Structural, go into Insert, and you will be given a long list of different boundary conditions to use. We went simple with just a force and a fixed support, but you are certainly welcome to play around with some of them to see how they actually operate. Just select the faces and/or lines that you want these conditions to be applied to using the geometry selecting tools above the model. Again, be careful, because too many tasks for the program to control will lead to very large loading times.
To actually get the results of the simulation we plan to run, we must enter the solutions we want the program to solve for. To do this, select Solution, select Insert, and you will be given a list of the different solutions that you would like the program to solve for. Make sure to apply the solution type to the geometry otherwise you will get no results. From there, if you have completed all of these steps correctly, you are ready to select Solve!
To understand the results, go into your solution on the left hand menu, once it has finished solving. Here you will be able to see contours of the questions you asked the software to solve. For instance, if you are running a static structural analysis, you should have asked the software to tell you deformation. Feel free to click through each of your asked solutions. While doing this go through mental checks to make sure that what the computer has solved fits what should have happened. Does the part deform the right way? Does the temperature distribution look right? If the answer to any of your mental checks doesn’t fit what should have happened then go back through your setup to ensure everything is correct. ANSYS does a great job of solving what you give it, but it doesn’t know what is “supposed” to happen; it just solves from what you enter.
Once you have gone through your mental checks and confirmed that it is following expectations, feel free to tentatively trust the results. To stress again, while ANSYS is great at simulating, at the end of the day, all it does is simulate what would happen as accurately as it can. Always use simulating in conjunction with hand calculations, scale model tests, etc.
Definitions/basic examples of FEA and CFD, plus any other general methods
Finite Element Analysis (FEA)
At the time of writing CONVERGE is hosted on a server administered by Aled Cuda, the current Sims Lead. In order to access converge you must contact him for the information necessary to VNC into said server. Although it is possible to install converge on your computer, this can be a highly involved process, and I guarantee you this server is plenty powerful.
When you receive your username you will receive a message that looks like this
Example, actual parameters may differ
Using these values and the vnc client of your choice vnc to gw.ld-cd.net, you should be greeted with a desktop like this:
Center right you can see the icons for converge studio, and a terminal appropriately configured for use with converge.
Although converge does support running jobs in serial from converge studio, any reasonable job will take ridiculous amounts of time to execute. In order to execute a job in parallel, open a converge terminal and do the following:
The server has two Intel X5690 processors for a total of 12 physical and 24 logical cores, so adjust the number of jobs (-n 24) as you see fit.
Theory behind simulations, the verification/validation process, conceptual explanation of processes behind general simulation methods.
The steps involved in designing and running a simulation are as follows:
Translate a physical problem to a mathematical model
Go through some procedure to find a numerical solution
Post-processing (such as interpolation) to generate output
Compare output to back-of-the-envelope estimate and/or experimental data
Not all of these have to be done manually, and simulation interfaces such as ANSYS will not show that all of this is happening. But users should be aware that this is what the program is doing, as well as roughly what the mathematical model consists of for each major mode of analysis (CFD, FEA and so on).
This step essentially converts the physical problem (e.g. calculating a certain quantity, such as stress at a set of points due to some load, or drag force due to some specified airflow model) to the mathematical problem of solving a differential equation for each of those points. Completely solving these differential equations can be difficult or impossible in practice, but fortunately, making accurate numerical estimates at specific points is computationally possible. A future update will explain how this process works; for now, check out the example in week 1 of the Cornell EdX class, "A Hands-On Guide to Engineering Simulations", for an explanation.
Solving a differential equation for a continuous body is impossible in general, given both the potential complexity of the equations (look at the Navier-Stokes equations for an example) and the arbitrary nature of the input geometry. Meshing is a process by which the arbitrary continuous input geometry is discretized. This means any valid CAD model can be converted to a mesh: a set of nodes with edges connecting them. Solving the equations for each of these nodes then makes the problem doable, and for a large enough mesh the difference between the exact solution and the discretized version is negligible.
Meshes work by representing each surface as a network of polygons, usually of 4 to 6 sides (but the examples shown use triangles). Here's an example of a mesh you might work with:
And here's an example of a mesh you almost definitely won't work with, but that shows how the procedure functions more clearly:
The simplest (but potentially less accurate) mesh generation uses triangles as the basic unit. This is simple because polygons of N sides can always be converted to triangles by connecting non-collinear sets of three points repeatedly (image)
This is a valid mesh, but not a very good one. All the triangles are long and thin, so nodes connected by a long edge may interpolate where doing so would not be accurate. (Linear approximations work well on small scales, but not on larger ones).
To solve this, we can introduce new nodes in the center of the shape. In order to avoid long and thin mesh elements that do not provide an accurate approximation, a minimum angle is set: all angles in each mesh surface element must exceed some threshold for quality (I've seen 20.9 degrees but citation needed). When an angle is lower than this threshold, the edges causing this small angle are replaced by edges with admissible angles.
The Delaunay algorithm (link) describes how to do this. Ruppert's algorithm is similar, with the introduction of the midpoint of each triangle. Its time complexity is greater, which may or may not be worth the extra accuracy depending on the case.
Boundary conditions are how you specify what happens to an object (as represented by a mesh). Since the underlying geometry does not contain information about the environment in which the part exists, we apply boundary conditions to simulate the external environment, such as airflow or an applied force.
Tutorial on how to safely and efficiently manage wires.
IREC has some requirements for safety critical wires. This is defined as wiring associated with drogue (or other drag device) deployment, main parachute deployment, and any air-start rocket motors. These requirements are summarized as follows:
“Individual wires should be bundled together to make a harness”
Twisted together
Zip Ties every 5 cm
Mesh sleeving ( should allow for inspection of wiring inside)
Harness supported by plastic P-clamps
All connected items by the harness should be rigidly fixed and cannot move
Allow some slack in the wire
Wires should allow for some slack but avoid excess length when possible. Dedicated wire support can be mounted on the walls so wires can be run-through them conserving space. Wires can also be labeled so that they can easily be distinguished in a timely manner.
IREC wiring requirements and suggestions can be referenced starting at page 23 here:
A tutorial on how to set up and run a 3D CFD simulation in SimScale
The SimScale interface steps are mostly self-explanatory, but there are some subtleties to running a simulation that won't be apparent from just clicking through. Most of these will carry over to ANSYS, so it's definitely useful to gain experience on this easier platform!
At the start, this is what you'll see. Upload geometry (which can be Solidworks, STL, parasolid, etc.), and you'll see the model on the right side. At this point, depending on the model, it might help to define a "topological entity set" (a set of faces on which the same operation can be defined). The model being used for this demonstration isn't too complicated, but with more intricate models like full rockets, it will help to define these.
Now, click on "Meshes", and assign the model you just uploaded as base geometry, then save. You can now start a mesh operation. You'll see multiple types of meshes you can make:
Tet-dominant
Hex-dominant automatic
Hex-dominant parametric
Hex-dominant automatic "wind-tunnel/external flow"
Hex-dominant (beta preview)
You can hover over each of these for an explanation. To estimate drag using CFD, hex-dominant automatic "wind-tunnel/external flow" is a good option if specific control is not required, and hex-dominant parametric allows for additional customization. Apart from the beta preview, all the hex-dominant modes are exclusively for CFD; SimScale will throw an error if you set up an FEA simulation using one of these meshes.
Fineness is on a scale of 1-5; usually, any setting greater than 3 risks timing out (but not always). "Inflate boundary layer" should be left on if turbulent flow is being simulated. The number of computing cores can be set to a maximum of 16 on the free version. It's important in the meshing stage to set the wind tunnel dimensions; by default, it will only be big enough to include the geometry and will not give space for the airflow. The dimensions of the wind tunnel box should be adjusted on the axis along which the geometry has axial symmetry.
Although symmetry boundary conditions can be set in the simulation designer, it is also possible to reduce effort at the meshing stage due to symmetry. This can be done by adjusting the bounding box as well. For rockets, this will usually include only one of the fins. In this case, a 2D simulation would also suffice (of just a small slice of surface area, which can be extrapolated around the whole 3D surface due to radial symmetry) but for the demonstration, 1/4 of the object will be taken.
After a while, the mesh will finish (you can read the Meshing Log to see how far along it is, while you're waiting!) and you'll see something like this:
Note that here the wind tunnel is hidden. You can make it visible in the tree to the top-right, but making it visible usually makes the viewer look weird.
Once you've got a finished mesh, you can move to the Simulation Designer. Click on "Simulations", then "New" and select Incompressible or Compressible (for this case, Incompressible, but if the speed of the flow is greater than Mach 0.3 it should be Compressible). The turbulence model can be set to Laminar if turbulent effects are not desired (if you didn't select "Inflate boundary layer" in the mesh designer). The difference turbulence models will be tested and written about in a future update.
Select the mesh you just made as the Domain, and add Air (from the material library) as the material for the bounding box, unless you're making a submarine. Set 1atm (101325 Pa) as the initial condition.
The most important part of this setup is the boundary conditions; a simulation is almost completely determined by its governing equations (set by the simulation mode, such as CFD incompressible), its geometry (set by the mesh) and the boundary conditions, so it's important to set these correctly. Boundary conditions have to be set for every face (which is why it's useful to have topological entity sets, from the mesh creator); if in doubt, set any surface's boundary condition to "Wall -> Slip" (not no slip, which is the default, if it's part of the mesh as opposed to part of the boundary). Adding a symmetry boundary condition along the faces with axial symmetry will make computation easier.
The essential boundary conditions to add are a velocity inlet at the front of the wind tunnel box (the velocity can be set as a constant, or as a function of any of x, y, z, t) and a pressure outlet at the back along the axis of symmetry. You can set the velocity based on whatever seems reasonable, and the pressure outlet should also be at 1atm.
(This mesh should actually be a bit wider on the sides, will update when I can)
The last set of relevant parameters is under Simulation Control. For a steady-state simulation (time-independent), the specific time values do not matter, but the (end time value - start time value)/time step length is the number of iterations that will be run. SimScale caps the maximum runtime so that you don't run through all your core hours doing way too many iterations of one simulation, but you can adjust this so that more iterations can be run. The default is 1000 iterations; it's 200 here for the sake of runtime, although the quality may be reduced because of this.
To see the quality of results, SimScale will provide a convergence plot, which is a graph of different parameters in the simulation. The closer to flat this graph gets, the better.
The runtime bar is slightly nonlinear; it may not make any progress for the first 15 minutes. That's okay! If it increases to 0.1% after that and doesn't move for another 15 minutes, that may not be okay; consider redoing your setup at that point. You can also read the solver log if you're curious about what it's doing.
SimScale will send you an email once your simulation is done, so you can check the results using the post-processor or download them.
In the post-processor, select "Results" then the variable to be shown. (Haven't really looked into this too much yet but here's what you'll get - to be updated later).
After creating an account, you can view tutorials for FEA, CFD, and Thermal analysis at https://www.simscale.com/tutorials/
Public Sample Projects
Sample projects on Sim Scale's Public Projects are one of the most useful ways to begin familiarizing with SimScale and the general mechanics of a computer simulation. Pay special attention to the mathematical models used and the different kinds of meshing algorithms. SimScale usually provides a brief explanation for the mathematical model or the meshing algorithm if you hover your mouse above it. The explanation usually includes remarks on what type of simulation the particular model or algorithm is suited for. If you encounter difficulties in setting up the initial mesh, a quick way to get around is to look for similar projects on SimScale's forum and reference their setups. Two links for CFD simulation will be provided below for initial references.
General tip
The latest ANSYS (19) contains 2 CFD modules: Fluent & CFX. While CFX is easier to set up, it yields few useful data - not even the drag force. Therefore, we usually use Fluent. Everything below will be about Fluent.
(with all due respect to our Testing sub-subteam)
This is one of the best tutorial videos of Fluent we have found. Follow through it and you will be able to do all that the team needs now.
The CAD model quality is crucial. It doesn't necessarily need to be very detailed, but here are some qualities that will ease the simulation tasks:
Air-tight. It should be a single continuous entity because what we will simulate is not its interior, but a block of fluid with a rocket-shaped hole cut from it. Do not let air inside the rocket.
Aligned. If it is radially symmetric (which is usually the case for a rocket), please make sure the main axis coincides (not just parallel) with one axis (ie. the z-axis) so that the rocket sits on the origin of e.g. the x-y plane. A radially symmetric body is probably also axially symmetric. Make sure the CAD is symmetric about the x-z plane (or y-z plane) so that if you slice it along the plane (see tip 6), it will fall into two identical parts.
Empty. CFD is about the airframe only and does not need the interior like the pretty avionics, as long as the center of mass is set right. You can save 'only the outer parts' when you export an Assembly to a Part in Solidworks. You can also save only the outer surfaces, but we have not figured out how to meld the 2-D surfaces into a body that can be processed in ANSYS - it only takes 3-D bodies.
Blunt (optional). Non-differentiable sharp points such as the nose cone tip may or may not yield errors in meshing. Still, you want some accuracy in the nose cone shape. Slice an infinitesimal amount off the tip, for example.
No overlap. It may sound silly, but redundant parts may arise when different teams build separate CADs and piece them together. The overlap will become physical nonsense in ANSYS.
No surface, only solid bodies. A tutorial for fix surfaces in ANSYS DesignModeller is below
If the full CAD does not work even after repaired with the tricks described later, to make a 'wind-tunnel model' from scratch that has nothing except what is needed in CAD. Particularly, make one single body that has the body, fins, boat tail, etc. all in one piece. Made properly, the wind-tunnel model should look boringly monochromatic in SolidWorks.
How to improve the CAD after it is done? With built-in CAD tools in ANSYS, specifically Design Modeller (DM, round green icon) & SpaceClaim (SC, square blue icon). SC is the default and is newer, prettier, and more intuitive at first glance, but it is hard to be precise in SC. Therefore, we usually use DM. Select DM from the right-click menu and do NOT double-click - that will pull up the default SC (unless you have changed the options), which can freeze the program for long. Still, it is easiest to make a good CAD in Solidworks in the beginning. DM is for CFD-specific polishes, which are often unavoidable.
You may have realized that our usual SolidWorks .SLDPRT is not a valid CAD format for ANSYS, because SolidWorks is a licensed software not willing to work with ANSYS. Furthermore, SolidWorks' own CFD software less capable than ANSYS. The solution is to convert the CAD file into something compatible, .x_t or .step for example. Usually .x_t is the best because it conserves certain parameters and is well-compressed.
The Repair & Merge tools in DM's Tools menu & Body Operation - simplify in Create are very useful in simplifying the model for CFD - detail is trivial. Try them one by one on your CAD. Pls be aware that Merge can take very long on over 500 entities & cannot be paused or stopped, so save everything and ensure power supply beforehand.
Cylindrical enclousres are more useful for our radially symmetric rockets.
Make a moderately-sized enclosure to ease computations with the 'Details' options in the lower-left corner. The diameter of the cylinder is usually 3 times that of the rocket (fins included). Leave much more space on the hind than on the front
Slice axially symmetric models into halves/thirds/quarters because they would yield the same results anyway. It also helps you to see the interiors and check whether there are leaks. Remember to multiply back certain results like drag in the end.
Name surfaces in the right-click menu before you close DM - not only the inlet etc, but also where you want to take data (e.g. you may want to know the drag on the sides of the fins). Use Ctrl to select multiple surfaces and name them into a same Named Selection.
If meshing fails, slice different sections to debug, just as you would comment out sections of buggy code. However, it is better to go back to Tips 5 & 8 and simplify the model first. (We are trying to develop custom meshing code as a last resort)
Try parallel processing if you can, even locally. CFD is a computationally intensive tasks.
Explore models for solution and their options. We usually try Transient SST because we heard it is an eclecticism between k-omega and k-epsilon. The Help button below the Edit... button lists their pros, cons, and underlying science.
Average over iterations for Monitors, e.g. over 5 iterations. This is averaging not over time, but over calculations.
We usually need around 500 iterations for mere convergence. Yes, convergence of quantities is key (and the primary pain) in CFD. We usually decide whether it has converged by looking at the plot by eye.
Try double precision in the options when you start up Solving if the result does not converge or look realistic. U do not usu. need it tho
Animating too many pathlines may freeze the frail old computers in the CAD lab. Be cautious when you set the default setting for step size/number.
Like @Turbulent CFD Memes for Aerodynamic Teens on FB. Most of the memes on this page are from there.
2D surfaces break the process of enclosing the model with a fluid domain. They can be identified in DM by the Surface ('flag') icon in the Bodies tree
To fix them:
Create new part and make a Named Selection for every cluster of surfaces that can make a solid
Tools > Merge. First the edges, then the faces
Tools > Surface patch to fill gaps in surface body
Use Create > Body Operation & select Sew in the options to convert the surface body to a solid body. Be sure to turn on Create Solid
Supress original surfaces. Select them from yr Named Selection, so that only the solid remains
Body Operation & select Simplify to make the solid sim-friendly
Velocity inlet boundary conditions are used to define the velocity and scalar properties of the flow at inlet boundaries.
Pressure inlet boundary conditions are used to define the total pressure and other scalar quantities at flow inlets.
Mass flow inlet boundary conditions are used in compressible flows to prescribe a mass flow rate at an inlet. It is not necessary to use mass flow inlets in incompressible flows because when density is constant, velocity inlet boundary conditions will fix the mass flow.
Pressure outlet boundary conditions are used to define the static pressure at flow outlets (and also other scalar variables, in case of back-flow). The use of a pressure outlet boundary condition instead of an outflow condition often results in a better rate of convergence when back-flow occurs during iteration.
Pressure far-field boundary conditions are used to model a free-stream compressible flow at infinity, with free-stream Mach number and static conditions specified. This boundary type is available only for compressible flows.
Outflow boundary conditions are used to model flow exits where the details of the flow velocity and pressure are not known prior to solution of the flow problem. They are appropriate where the exit flow is close to a fully developed condition, as the outflow boundary condition assumes a zero normal gradient for all flow variables except pressure. They are not appropriate for compressible flow calculations.
Inlet vent boundary conditions are used to model an inlet vent with a specified loss coefficient, flow direction, and ambient (inlet) total pressure and temperature.
Intake fan boundary conditions are used to model an external intake fan with a specified pressure jump, flow direction, and ambient (intake) total pressure and temperature.
Outlet vent boundary conditions are used to model an outlet vent with a specified loss coefficient and ambient (discharge) static pressure and temperature.
Exhaust fan boundary conditions are used to model an external exhaust fan with a specified pressure jump and ambient (discharge) static pressure.
--from http://jullio.pe.kr/fluent6.1/help/html/ug/node177.htm
Connecting to the CalSTAR server for maintenance
Be very careful when making server changes. Changing certain items such as processor count, RAM size, disk size, and backup services will incur additional charges. Do NOT change our subscriptions, services, plan, or anything relating to billing without discussing with all leads. You will be responsible for any changes in payment.
CalSTAR pays for a cloud server from Microsoft Azure. It is a very weak virtual machine (VM), meant only for low intensive tasks like licensing, product data management (CAD version tracking), and simple scripts (Discord/Slack bots).
The server is currently on the Basic A1 (1 vcpus, 1.75 GB memory) plan with 127GB of disk space.
As of the time of writing, this is CalSTAR's only server (with the exception of a Berkeley OCF web server hosting our website). This means the server is the one you probably have connected to in the past for Solidworks Workgroup PDM and Converge CFD Licensing.
If you simply want to look at resource status (CPU Usage, RAM, Network Activity, etc), some of this information is available on the Azure portal.
Login information should have been provided to you upon becoming a lead/admin. If you are not a lead/admin please contact one if you believe something is wrong with the server.
Selecting the option in the left white box pdm2 - Virtual machine will open the dashboard for our server (exact location may differ, ensure you select the pdm2 - Virtual machine option).
The dashboard contains most information you will need, including CPU usage, RAM usage, Network usage, Disk usage, Public IP, and links for more actions.
If you need to do more than view resource status, and need to mess with specific features within the server VM, you will need to connect to the server's Virtual Private Network (VPN) and open a Remote Desktop Protocol (RDP) connection to the server. The following steps will cover how to do both.
Previously, the server was accessible through a Remote Desktop Connection to a public IP address and port number. This has been intentionally disabled for increased network security. You must now first connect to the VPN and RDP with <server's local IP address>:3389.
Basically connect to the server's Virtual Private Network (VPN) like you would for the Solidworks Workgroup PDM or other software licensing (Converge CFD). If you have not done so before, or are not sure what that means, follow this guide.
For all systems, download the Remote Desktop Protocol file 'pdm2.rdp' here.
The RDP file can only be downloaded when signed into Google Drive with a berkeley.edu account.
Simply run the 'pdm2.rdp' file downloaded previously. It should automatically launch Remote Desktop Connection (RDC, a Windows Program that implements RDP) and prompt you for credentials.
If Remote Desktop Connection does not launch on its own, open it by searching the Start Menu or by pressing [⊞ Win + R] and entering
Click Show Options and click Open in Connection Settings. Locate and open the downloaded 'pdm2.rdp' file. You will be prompted to login if done correctly.
Computers without RDC (Linux, Mac, unusual Windows installations) will need to find a program that implements RDP. A decent alternative is FreeRDP, however, some knowledge of the terminal/command prompt is necessary to initiate a connection. Documentation for FreeRDP can be found here.
While functional, a FreeRDP connection is slower than a standard RDC connection. If at all possible, it is highly recommended to connect to the server from a standard Windows installation.
The following information for FreeRDP on Linux and Mac is untested. Please troubleshoot yourselves or contact the current/previous server admin for more information. Please update this wiki if or when you figure out how to properly use FreeRDP.
For Linux and Mac, install FreeRDP using your preferred package manager. Use the command below to connect to the server.
So as an example:
You will be prompted to login if done correctly.
The following instructions for Windows may be difficult without basic knowledge of the Command Prompt, specifically howcd
and dir
work. More information can be found here [wikipedia].
For Windows, download the program, and unzip the files to a new folder. Copy the downloaded 'pdm2.rdp' file into the new folder. Open the Command Prompt by searching the Start Menu or by pressing [⊞ Win + R] and entering
Using the Command Prompt, navigate to the new folder and run the following command:
You will be prompted to login if done correctly.
Basically either the computer, the server, or both have outdated security programs. Updating the server and/or your computer will usually fix this issue. If not, follow the steps in Resolution on this website.
Avoid using the Workaround in the link above.
Guidelines for how to keep CAD documentation consistent within STAR
Conventions for CAD documentation of parts designed for use by STAR can be grouped into 2 categories: drawing setup and filename conventions.
Regarding drawing setup, CADs for the purpose of documentation should use the drawing template and use Imperial (also known as IPS) units. Furthermore sub-assemblies should be placed in external files (a tutorial of how to do this is soon to come).
Regarding filename conventions, file names of CADs should adhere to the following guidelines:
File names shall follow the general convention of: Project_Subteam_DescriptiveName[_McMaster part #]. See below for project and subteam codes.
An example of this might be IREC20_PAY_Payload_Centering_Ring.SLDPRT for an in-house part or IREC20_AIR_Weld_Nut_90611A320.SLDPRT for a McMaster part.
Similarly an example for an assembly might be IREC20_AIR_Nosecone_Assembly.SLDASM
File names shall not contain special characters (e.g. "!@#$%^&*()?/|\" ) aside from "_". Hyphens shall be allowed only if part of an external part number. Spaces and periods (outside of ".SLD***") are not permitted, as they can cause filepath issues.
Subteam shall be denoted by its appropriate 3-letter abbreviation:
AIR : Airframe
AVI : Avionics
PAY : Payload
REC : Recovery
PRO : Propulsion
SIM : Simulations
OUT : Outreach
Project shall be denoted by the selected abbreviation for the project:
MINDI: 2" minimum-diameter rocket
IREC20 : 6” diameter rocket design for IREC 2020 (this is Bear Force One, the project started before it was named and before IREC 2020 was moved to 2021)
LE165 : “Hot Take”, Propulsion’s first-iteration of a liquid engine
LE1: Liquid Engine 1, Propulsion's 2020-2021 "simple" engine
LE2: Liquid Engine 2, a multi-year project to design and build a higher-performance engine. Custom tank CAD can also use LE2.
SSEP: Stage separation demonstrator
DAVE: Deployable aerial vehicle experiment, a payload launching on Bear Force One.
CAS: Common Avionics System mission(s), flown on AirBears. AirBears (the vehicle) was developed before the naming convention became mandatory, but all CAS-related CAD should follow the convention.
A brief overview of the proper steps when manufacturing a tube using the X-Winder.
Always wear gloves when handling epoxy and composite fibers.
Keep hands, feet, hair, etc. out of the way of the X-Winder when in operation. It is a large machine and there is a good chance it could cause as much damage to you as it will to itself.
When using ovens, avoid accessing them while hot, and wear necessary safety equipment when handling hot objects.
Select the desired tow spool and epoxy. The epoxy that is used should have a setting time that is longer than the estimated wind time to avoid issues with X-Winder operation.
Ensure the X-Winder is clean and in working order: motors turn smoothly without overheating, tow spool rotates freely, belts are secured tightly, no residual epoxy, etc.
Mount the desired mandrel to the main rod, making sure that everything is tight and does not slip when rotated.
Make accurate measurements of the tow line and the mandrel, as well as the start and end lengths of the wind pattern. (Note that generally the ends of a wind are inconsistent with the bulk, so it is best to wind 2-3 in. longer than the desired tube length and then cut to size after.)
Input these measurements into the X-Winder software along with desired wind angles and layer count.
Cut a piece of bleeder/breather cloth that will fit around the mandrel for use after the wet wind.
Depending on the estimated wind time, this is a good point to think about pre-heating the curing oven to the desired temperature.
Pull the tow through the rollers to the delivery head. Be sure to place the line between all spacers and check that no fraying occurs as the tow is pulled through.
Tie the end of the tow to the mandrel slightly ahead of the start location such that the knot is not wound over. This knot has to be secure since there will be significant tension as the wind starts. Tape can be used to help secure the knot.
Run the software for part of a layer, checking for proper spacing of the wind and wind behavior at the ends of each pass. It is a good idea to check each different wind angle and verify that things look good and the X-Winder is working as intended.
If everything is good to go, cut the tow and unwrap the partial wind. Remove the mandrel to prepare it for a wet wind.
Wrap the mandrel in wax paper such that the paper is snug to the surface but can still slide off without too much effort. The wax paper should be longer than the intended wind length but shorter than the mandrel. Tape the ends of the paper to the mandrel so that it cannot rotate independently during winding.
Apply several thin coats of mold release agent to the surface of the wax paper, allowing 5-10 minutes to fully dry.
Place mandrel back on the X-Winder, making sure that starting and ending wind measurements are within the wax paper region.
Mix one pump of resin and hardener and pour into the epoxy tray. Pull the tow through the tray until epoxy has reached the delivery head. Ensure that the epoxy regulator is properly tensioned.
Tie the end of the tow to the mandrel slightly ahead of the start location such that the knot is not wound over. This knot has to be secure since there will be significant tension as the wind starts. Tape can be used to help secure the knot.
Run the wind program. Watch to make sure things are running smoothly and that the first few passes are looking good.
Every 10-15 minutes, check the epoxy tray to make sure there is enough to cover the bottom part of the tray. Do not overfill the epoxy tray, as this will cause a buildup of heat as the polymerization reaction occurs, which can melt the tray or cause curing inconsistencies.
It is good practice to pause after each layer just to give everything a quick inspection before proceeding.
At the end of the wind, cut the tow and take a moment to appreciate the fact that the hard part is over!
Wrap the wind in one layer of bleeder/breather cloth. Try not to overlap too much as it might dry out the surface.
Tape and secure one end of a roll of shrink tape just off of the end of the wind. Run the shrink tape program or simply have the software spin the mandrel as you slowly wrap the shrink tape around the wind. Be careful: try to avoid wrinkling the tape and keep an even overlap as you move across the wind. Cut and secure the other end once the wind is completely wrapped.
Remove the mandrel and rod from the X-Winder and place in the curing oven. (The temperature should be above the activation temperature of the shrink tape.)
After the wind has been completely cured, cooled, and removed from the oven, the shrink tape and bleeder/breather cloth can be removed.
Remove the tape holding the wax paper to the mandrel, then remove the composite tube from the mandrel. Peel away the wax paper from the inside of the tube.
Congratulations! You have produced a composite filament wound tube. Inspect it for any defects or flaws and appreciate its cool pattern. It is now ready to be cut, sanded, turned into a rocket!
Disassemble the parts of the X-Winder which touched epoxy. Thoroughly clean these using a solvent such as acetone.
Check for and remove any fraying residue and clumps in and around the area.
Discard any epoxy mixing cups, used shrink tape, used bleeder/breather cloth, excess tow, and all other waste.
Make sure the X-Winder is unplugged when not in use.
2D Tutorial
Instructions: https://docs.google.com/document/d/1l5zS3rDZNhere1akOaFCs_O0VW4Dil8Atkec5RnhjSo/edit
ISOs: https://drive.google.com/drive/u/1/folders/1grdEHUKfftCNnkoH3mhTrcDQaJvqN3aE
This tutorial introduces the general ANSYS CFD workflow which can be summarized in four steps:
Geometry (SolidWorks)
Mesh (ANSYS Meshing)
Setup/Solve (Fluent)
Results (CFD-Post)
While geometry creation is possible in ANSYS with the Design Modeler module, we will primarily be using SolidWorks to create our geometries.
For 2D simulations, our geometry consists of a surface that represents our fluid domain. This means that you will cut out the area of any objects (ex. Airfoils, Fin Profiles) from the whole domain. The picture below shows the example model that that we’ve already prepared for this tutorial (2D_Test_v2.SLDPRT).
Download the SLDPRT file to your computer first before going to your Start Menu and running Workbench 17.1/19.2, which looks like this by default:
Workbench is the digital “workbench” where you set up simulations to run. The blank slate under “Project Schematic” is where you layout the different system blocks available to you in your Toolbox on the left.
Begin by dragging and dropping a Geometry block into the Project Schematic workspace. You may have to click the + next to Component Systems to expand the list.
Right click the cell of the Geometry block with the “?” and import the SolidWorks part.
The next step is meshing, which is the process of discretizing our fluid domain into elements and nodes. A high level view of how CFD works is that the solver takes your mesh and solves a set of fluid equations for each individual element.
Element size can be considered the ”resolution” of the mesh. In general, we want more elements (aka smaller elements) in areas that we expect to see high changes in pressure and/or velocity. For example, we try to use inflation layers in areas where we expect a boundary layer to form. Areas further away from our interest areas are allowed to have larger element sizes because there will be less change within an element in those areas.
Click and drag a Mesh block over the Geometry block you just created. A new Mesh block will appear, with a line connecting it to the Geometry block. This indicates that it is pulling geometry information from the Geometry block.
Double click the Mesh cell to open up ANSYS Meshing in a new window.
In ANSYS Meshing, you will first need to make named selections. These will mainly be used in Fluent later to create boundary conditions.To create named selections, Ctrl+ left click to select all the edges you want to be grouped together. Then right click and select ”Create Named Selection.” If you’re unable to select edges, press Ctrl+E to switch to edge selection mode, or go to the top of the window and select the icon.
You may also find it useful to switch to Box Selection mode when selecting multiple edges at a time.
Create named selections for the wings (WINGS), ground (GROUND), left edge (VELOCITY-INLET), right edge (PRESSURE-OUTLET), and top surface (SYMMETRY). Then switch to surface selection mode, select the entire surface, and name it FLUID.
Now we’ll specify our meshing settings. To enable meshing options, select ”Mesh” from the outline on the left. In the Details panel in the bottom left of your screen, expand the sizing options. Set the following settings:
1. Size Function: ”Proximity and Curvature”
2. Relevance Center: Fine
3. Smoothing: High
4. Span Angle Center: Fine
5. Num Cells Across Gap: 10
6. Min Size: 0.001m
7. Proximity Min Size: 0.001m
Then use the Mesh Control menu to set local mesh parameters.
First select Sizing. Select the edges of the wing, then click ”Geometry” in the Details panel. Select the ”Apply” button to set the selection. Then set the element size to 0.0005m. After that, select Refinement from the Mesh Control menu. Select the surface for the geometry selection. Set the refinement to 1. After this is done, right click “Mesh” in the Project tree and select “Generate Mesh”. Once the mesh generates, you should be able to the outline of how the program divided the surface into individual elements. Save the project and close the ANSYS Meshing window.
Now that we have our mesh, it’s time to read it into our solver. Click and drag the Fluent block over the Mesh block to add and connect. Double click Setup, and when the Fluent Launcher window opens up choose Parallel processing and input the number of processors your computer has under processes. You can find this by going to the Performance tab of Task Manager and seeing how many “Logical processors” your computer has. If your computer has graphics cards, you can enter them under GPGPUs.
Once Fluent loads the mesh, go to the Tree on the left side and:
Select Models. Select “Viscous” and click “Edit”. Under Models, select “Reynolds Stress (5 eqns)”. Keep everything at default values and press OK.
Select Boundary Conditions on the left Menu. If you did the named selections correctly, you should have named selections for the ground, interior-fluid, pressure-outlet, symmetry, velocity-inlet, outlet, and wings. Select velocity-inlet and make sure the type is also “velocity-inlet” (you should now be able to see why we named the selections the way we did). Click Edit and change Velocity Magnitude to 20 m/s. Then, select the ground, make sure the type is “wall”, and click Edit. Change the wall type to moving wall and change the speed to 20 m/s. Make sure the direction of the movement is in line with the inlet velocity (should be in the X direction). Then select the pressure-outlet and make sure the type is ’pressure-outlet.’ Click edit and make sure the pressure is 0 gauge pressure. For symmetry, make sure the type is “symmetry”.
Select Solution Methods from the Tree. Change the scheme to “Coupled”, and the Turbulent Kinetic Energy, Turbulent Dissipation Rate, and Reynolds Stresses all to “Second Order Upwind”. Then check the box for “Pseudo Transient”.
Select Solution Controls from the Tree. Change the following values: Pressure to 0.5, Momentum to 0.5, Turbulent Kinetic Energy to 0.75, Turbulent Dissipation Rate to 0.75, and Reynolds Stresses to 0.75.
Select Monitors. Click “Residuals” and select “Edit”. Change Convergence Criterion to ’none.’ Click OK. Then, under ’Residuals, Statistic and Force Monitors,’ select lift from the create menu. Check the boxes for “Print to Console” and select wing as the wall zone. Make sure the force vector is the right direction (should be Y). This will create a plot of the coefficient of lift per iteration while running the simulation.
Select Solution Initialization from the Left Menu. Select Hybrid initialization and click initialize.
After the Console tells you that initialization is done, click Run Calculation on the Left Menu. Put in 50 iterations in the number of iterations and click calculate. Watch the convergence plot. Make sure the residuals and/or the CL is converging. For the residuals, this means that they are below 1e-02 times smaller than they were in the beginning. For the CL, it means that the plot ends up at approximately one value over many iterations. Continue calculating in 50 iteration sets until the simulation converges.
Once done with the simulation, click Reports from the left menu. Select “Forces” and click Set Up. Select the wings as the wall zone and specify the direction vector such that lift is shown. Press Print and the amount of downforce will be reported in the console.
While we can pull downforce numbers from Fluent quite easily as you just saw for yourself, in many cases we want to be able to visually see our flow to determine how the flow is actually behaving. Close the Fluent window and add a Results block to the Project Schematic. Double click the new block to open up CFD-Post.
First, let’s add a Contour to see what our velocity and pressure distributions look like. Click the Contour icon at the top of the screen.
Then for Locations, choose symmetry 1. For # of contours, select 20. Press Apply to generate the plot. Play around with # of Contours to see how the visualization of the pressure distribution changes. Then, add another Contour but select Velocity as the variable instead.
Next, let’s add a Streamline to see flow behavior. Click the Streamline icon to the right of the Contour icon. Specify the streamlines to start from velocity inlet, and change the # of points to 50. Click Apply to generate the plot.
Instructions: https://docs.google.com/document/d/1l5zS3rDZNhere1akOaFCs_O0VW4Dil8Atkec5RnhjSo/edit
ISOs: https://drive.google.com/drive/u/1/folders/1grdEHUKfftCNnkoH3mhTrcDQaJvqN3aE
3D Meshing & Fluent Guide v2
DesignModeler
Notes:
After pretty much every step, you will need to update your geometry by clicking “Generate”. For the sake of clarity, it’s not included in this guide.
SAVE OFTEN
Ansys defaults to metric, so all dimensions following this will be metric unless otherwise stated.
If DM gives you errors/issues about your geometry, try Boolean uniting your imported CAD into one solid piece
DM allows you to hide individual faces by right clicking on them and selecting “hide face”. This is useful for editing your model after it’s been subtracted from the fluid body.
Import your STP or SW file: File -> Import External Geometry File
Again, this is possible in SolidWorks, this way is just less buggy.
Create a box that contains everything you want to simulate and then some. For half car sims, we’ve generally been using the two points method with (-8,-3,0) and (15,0,4).
You should see that this creates a box surrounding the car with one wall going down the centerline of the car.
Boolean out your imported CAD model from your box: Create -> Boolean
Set Operation to “Subtract”
Target Body -> Fluid
Tool Bodies -> CAD model (could potentially be multiple bodies)
At the base of anything protruding from the box, you should see rectangular-ish holes
Put a fillet on the edge of this hole traditionally (While not necessary, it can reduce errors). Create -> Fixed Radius Blend
Create your named selections: Tools -> Named Selections or right click on a face -> Named Selection
Coloring by named selection will make this process way easier and prettier looking: View -> Graphics Options -> Face Coloring -> By Named Selection
Note: Colors will only display on one side of a face, so this can look a little confusing at times.
Fillets will (unfortunately) create tons of little faces. Make sure you select all of them!
You do not have to get every face in one pass. Right clicking on a named selection allows you to edit the selections
Toggling visibility on a named selection also makes it extremely apparent if you’ve forgotten to select a part of it.
ICEM
Tips:
ICEM is very unforgiving, so be careful not to screw up
no pressure
For whatever reason, most of the icons aren’t named and instead you must solely rely on the little pictures. I’ve included names of what the icon looks like to try and make up for this.
Selections are made by left-clicking and confirmed by middle mouse
Right click deselects them in the reverse order of selection (ie, newest to oldest)
Setting your background to all black makes it easier to view your geometry: Settings -> Background Style
SAVE OFTEN
After importing your model, immediately repair your geometry: Geometry -> Cube and wrench icon -> Enter
If you see any yellow lines/surfaces, those are suspected to cause holes in your mesh, a fatal error. Go back to your model in SW and clean up/thicken the areas where you saw them.
Toggle the display of points and surfaces: Model Tree (on left side of screen) -> Check off points and surfaces
Deselecting curves can help declutter your screen
Create fluid body: Geometry -> Cube and pencil
Change part name to fluid
Select two opposite corners of your bounding box by clicking on them
Set your mesh parameters:
Mesh -> Cube and two globes -> Set Global element seed size -> max element to 1 m
Within the same dialog on the lower left, click on the orange triangular icon with the gears
Scroll all the way to the bottom and click on “Advanced Prism Meshing Parameters”
Select “Do checks’ and “Do not allow sticking” and apply
Set your part mesh parameters: Mesh -> Cone, cylinder, and sphere
See here for the settings.
Notes:
Increasing number of layers and decreasing maximum size causes computing time to increase dramatically. Halving your maximum size will lead to far greater than two-fold increase in time. Make sure that you are only being as accurate as you need to be.
Example pic:
Create points for your mesh densities: Geometry -> Three black dots and pencil
You can place points using the following tools:
Computer screen with dot places points wherever you click (Quick, but inaccurate)
Circle with 3 dots allows you to place points at the center of a circle (useful for wheels)
Two black dots and blue dot allows you to place points halfway between two other points
Blue arrow allows you to put point a certain distance away from a known location
Place points at the places specified in the settings doc.
Create mesh densities: Mesh -> Cube with rho
See settings doc again.
Notes:
To create a cylindrical density zone (the ones that are specified as “connected” on the settings doc), select both points before hitting apply.
Be very careful of accidentally creating nested mesh densities; they will make a bajillion elements and take forever
Large widths with small sizes will also take forever and make a bajillion elements
You can edit/delete densities by right-clicking on densities in the
Doublecheck all your mesh settings
If you’re simulating rolling wheels, copy down the locations of the centers of the wheels, you’ll need it during Fluent
Left panel -> Geometry -> Left click on points -> show point info
Copy down the output from the console to a txt file or something
It doesn’t matter where the point is, as long as it’s on the axis of rotation of your tire
Now you’re ready to mesh! Don’t run this on a laptop. It will take a very long time and probably fail. Archive your wbpj (in Workbench, click File -> Archive) and transfer it over Chrome Remote Desktop to one of the sim comps
Unarchive it. Open Workbench -> File -> Restore Archive
Open ICEM back up
Go into Settings → General and make sure you put the appropriate number of processors (32 for SC1 and SC2)
Now it’s time to actually mesh. Mesh -> Blue icon with colored arrows on it (on the far right)
Select create prism layers
Click compute!
Wait for meshing to finish
NOTE: A prompt may pop up asking you if you want to save the geometry. This typically indicates that the initial meshing has finished and ICEM is about to move onto prisms meshing. Select “No”.
After meshing has finished, scroll up in the console and ensure that ICEM has properly meshed prisms. You should be able to see lines of blue text that the prism mesher outputs.
Check your mesh: Edit Mesh -> Cube with red check mark. Hit apply.
Multi-face errors will crash fluent on orientation
This is different from multiple edge errors - Fluent seems to be fine with those.
If fix is an option for the error message, choose that. If it’s not, choose subset.
If your geometry has a hole in it, gg
Smooth your mesh: Edit Mesh -> Iron with multicolored background (not the iron with brown background)
Freeze Tetra 4, Penta 6, and Pyra 5
Set iterations to 20 and quality to 0.5 and smooth
Set everything to smooth
Lower quality to .2 and smooth
Repeat step o to check mesh one more time.
Fluent
Notes:
Error troubleshooting
Crashes before 1st iteration - remesh
Segmentation error - remesh
Floating point error - remesh
Use as many cores as you again (for most of our desktops, try 8). Don’t use double precision unless single precision gives you convergence issues and you don’t want to remesh
Models -> Reynolds Stress (7 eqn)
Boundary Conditions
Set inlet velocity and ground to 20 m/s (process is identical to 2D)
If using wheels:
Wall motion -> Moving Wall
Motion -> Rotational
Set xyz coordinates to whatever you copied down from ICEM
If you used the standard origin and orientation, you should be able to use the points on the settings doc.
Rotation axis direction should be (0,1,0), unless you made your model funny.
Speed: -87.5 rad/s
Alternatively, you can set this to positive and flip the direction of your rotation axis
Example:
Double check remaining zones (symmetry, chassis, etc)
Solutions Method
Scheme -> Coupled
Set Momentum, Turbulent Kinetic Energy, Turbulent Dissipation Rate, and Reynolds Stresses to 2nd order
Note: If you have convergence issue, try running the first 50 iterations with 1st order, then switching to 2nd order after 50 iterations
Enable Pseudo-transient
Solution Controls
Pressure: 0.65
Momentum: 0.35
Turbulent Kinetic Energy: 0.5
Turbulent Dissipation Rate: 0.5
Reynolds Stresses: 0.5
Monitors
Create lift and drag plots for whatever you’re modeling:
For Ansys 19.2 Top menu: Solving → Reports → Definitions → New → Force Report → Drag/Lift
Ansys 17 options are still in Monitors
Select residuals -> edit -> disable convergence criterion
Initialization -> Initialize
Initialization might fail. If it does, go to more settings -> set number of iterations to 15 or 20
Run calculation: Try starting off with 200-300 iterations
CURRENTLY UNDER EVALUATION. INSTRUCTIONS ONLY AVAILABLE FOR CONVERGE STUDIO (PREPROCESSOR) AND NOT CONVERGE (SOLVER).
There are actually two programs relevant here: CONVERGE and CONVERGE STUDIO. Both are included in our license. CONVERGE is basically the actual solver. CONVERGE is the program that will run your processed input files and return the simulation. CONVERGE STUDIO is a pre-processor where you can view geometries, set boundaries, set simulation options, and export these as input files for CONVERGE. CONVERGE STUDIO is also capable of running CONVERGE in serial, and validating the exported inputs with CONVERGE.
Select CONVERGE_2.4, then CONVERGE_Studio, then download the appropriate file for your operating system.
There are no special instructions for installation. Simply run your downloaded file and follow the on-screen prompts.
It will be helpful to make a note of your installation directory, as you will need it for licensing.
Since the software is no longer in use, and the license file has been requested multiple times by persons clearly not on the team, the license file is now unlisted and private. Please contact your current leads if you really must use the license file.
The license file can only be downloaded when signed into Google Drive with a berkeley.edu account.
Copy or move the 'license.lic' file into the license folder in CONVERGE Studio's installation directory. For Windows, the default location is
The file MUST be named license.lic or CONVERGE Studio will be unable to locate the file.
Once the license.lic file is copied into the correct directory, and you are connected to the server, simply launch CONVERGE Studio.
You must stay connected to the server while working in CONVERGE Studio. The program will perform a license check out/verification every few hours. This includes simulations. You must be connected during a simulation or it will be terminated after the next license check. Terminated sims can be restarted via the restart file.
For floating licenses, only 5 simulations can run at a time across ALL computers. Please make sure with the Simulations Lead that no other critical sims are running before you start yours.
Create the fluid body: Create -> Primitive -> Box
Tip: using the “two points” box type is generally much much easier than 1 point and a diagonal
Before:
After:
left panel
Refer to deprecation note in .
Converge CFD is a particle-based fluid dynamics solver. It is currently being evaluated by the Simulations team for full team usage.
You will need to make a new account, or log in with your preexisting account. Upon logging in, a file directory page will be shown.
The license for Converge CFD is a floating license. This means you must be connected to a licensing server in order to use the software. For CalSTAR, the licensing server is our only server, the PDM server.
Most people use it to mill PCBs but that's boring
The Othermill creates very dimensionally accurate parts, but may be slower and more complex than other prototyping processes. If your part significantly depends on being diemnsionally accurate (for example, low backlash gears), then the othermill may be a good choice. Laser cutters produce a noticeable and uneven kerf, and 3D printing (FDM) cannot produce very fine details well.
The smallest commonly available Othermill bit that can be used to mill out parts is the 1/32" bit. This bit can cut up to materials that are 0.125" thick. Be aware that machining speed can be significantly slowed down the smaller the bit size is. Refer to online resources on Computer-Aided Machining (CAM) best practices on what bit to choose.
In order of machinability, here are the materials the authors have used successfully on the Othermill:
Delrin (acetyl homopolymer resin)
Lexan (polycarbonate)
Aluminum
The Othermill should not be used to cut steel.
Download the Jacobs Hall tool library from the Jacobs Hall bcourses training for the Othermill. Do not download the tool library directly from Bantam Tools, as it contains some inaccuracies.
Measure the stock and CAD the part to be no greater than the thickness of the stock. If the part is mostly flat, have its thickness match the thickness of the stock unless facing is needed.
Set up the Work Coordinate System as follows. Other tutorials may recommend you set the origin at the top of the stock, but this can cause poor results and collisions with the spoilboard. While these toolpaths will be offset in the Z direction when we import them into the Bantam Tools software, we will correct this at a later time.
Input the accurate dimensions of your stock in the Stock tab. Then, adjust the position of your part relative to the edges of the stock. Items in red boxes should generally be changed for each part or stock piece, while the rest should match the image.
The term "feeds and speeds" refers to how quickly the tool rotates and how quickly it moves along the x, y, and z axis. Smaller tools should generally be used with slower feeds and speeds.
Aluminum is significantly tougher than plastics. most important is the stepdown on operations with multiple depths; use a stepdown of at most 0.004". For drilling, use a very conservative chip clearing toolpath, pecking in 0.001" increments at a speed of 0.5 in/min. Milling aluminum with the Othermill is somewhat of an acquired skill, so don't worry if you break a bit or two at first. Do not attempt to mill aluminum with anything smaller than a 1/16" endmill.
Climb milling will result in a better finish and longer tool life.
Check the "keep tool down" checkbox or cuts with multiple depths will lift the tool each time.
Always keep the Ramp checkbox checked and generally use a ramp angle of 3-5 degrees depending on the material (larger angle ok on softer materials).
Facing
Bore
2D Contour
Always simulate your toolpaths in Fusion before exporting them for use on the machine. This is the primary way to prevent damage to the machine, the tooling, and the part
Open the simulation settings and check the "Stock" box. You can change from the default green color by changing the material options, but this is not important. Watch the entire simulation; if it is long, speed it up as little as necessary to ensure you catch any unintended behavior.
Right click on each operation on the left dropdown and select "Post Process". Select the settings for the Othermill and give your toolpath a descriptive name and number: e.g. 1_facing, 2_bore, etc. Numbering will help you keep track of the order in which to run each operation.
This step will produce .gcode files; these are text files containing a list of instructions that will be fed to the Othermill during operation. Make sure you save the gcode files in an accessible location on your filesystem.
Turn on the Othermill using the power switch at the back left corner.
Ensure that the emergency stop (big red button) is not engaged.
Connect the machine to a computer that has Bantam Tools installed.
Open Bantam Tools, and home the machine.
If using the fixturing bracket, locate the bracket by pressing "locate".
Insert a 1/8" endmill upside down (with the cutting flute inside the collet).
Load the material (tbd)
Load the toolpaths. Click the "Open Files" button and select your .gcode files.
Offset the toolpaths. If you do not perform this step, nothing will be milled. For each toolpath, open the "Placement" dropdown and enter -[stock thickness] under the z-offset. For exampele, if I have a sheet of nominally 1/8" Delrin that I have measured to be 0.135" thick, I would put "-0.130 in". You may also add x and y offsets, but be sure to repeat the process for each individual operation / toolpath.
Load a tool by clicking "Change...". Mount the desired bit and select it from the drop down menu. Click "Locate" and ensure that the mill has moved the bit above a clear section of the spoilboard (metal bed). If not, manually adjust. Confirm the position, and the machine will begin to move the bit down to touch the bed. While this is happening, make sure you are ready to stop the machine (press "ESC" or the emergency stop to stop). Once the bit has made contact with the bed, the machine should immediately stop trying to move the bit down. If you head any sound of resistance STOP THE MILL and try again.
Tutorials specific for the Payload subteam. Since the payload team is quite broad, the most important tutorials are those referenced under General or Manufacturing.
Most of the tutorials under Manufacturing have been written by Payload members for Payload applications: