CAD Design
"Measure twice, cut once"
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"Measure twice, cut once"
Last updated
Was this helpful?
CAD (Computer assisted design) is an essential part of VEX robotics. It allows teams to fully plan out the robot on the computer before constructing anything in the real world.
Let's construct an (unbiased) table showing the advantages and disadvantages of CAD. If your team decides that the disadvantages outweigh the advantages, then don't CAD!
Plans out the robot fully ahead of time
None
Reduces the time it takes to build
Adds an element of professionalism to the engineering notebook
OnShape is the recommended software for CAD in VEX due to its ease of use and VEX part libraries, but other software work just as well. The table below shows the most common CAD software used for VEX Robotics.
Benefits
Cloud based -- good for collaboration User friendly UI Can run on less powerful hardware compared to Inventor Limited stress simulation tools
Wide support options
Specialized time-saving tools User friendly UI Requires somewhat powerful hardware Customizable stress simulation tools Almost everything is customizable
Drawbacks
Lack of traditional CAD capabilities such as constraints and simulation Limited uses
Lack of customizability Time inefficient
Limited support options Single user & local processing (although you can save files on a cloud drive so that multiple users may access them)
Introduction Video
VEX Libraries
Built into OnShape (check video)
As important as it is, CAD is not the end-all. It is a tool that you use to plan out where everything goes on the robot. However, no robot has ever perfectly matched it's CAD design, because there are more factors to consider in the real world. For example, it's not necessary to model screws in the CAD, since it is already clear where they need to be. On the other hand, important aspects of the robot--the drivetrain and additional mechanisms--should be present in the CAD, so that you know how to build them in the real world.
CAD Design can be intimidating at first; here's a few tips:
Don't be afraid to take inspiration from other robots. Watch matches online. Study reveal videos. Ask other teams questions at tournaments. If you see a design you like, imitate it--don't copy.
Imitate means "take inspiration from without copying screw-for-screw, and make it better along the way". It's okay to imitate other designs that work well. It's not okay to copy the entire robot, down to the last hole of the C-channels (i.e. holecounting).
Don't overthink the positioning of the brain, battery, and air tanks. These don't have to go in the CAD design, because their positioning can usually be figured out later.
Ask for help. Get experienced robotics members to review your CAD before you build it--this prevents you from having to take apart half of the robot to fix one minor flaw later on.
Simpler is better. A well-optimized simple design will beat a complex one nine times out of ten. Less mechanisms means less things can go wrong on the robot, so don't overdesign!
Here's some specific tips for VEX Robotics:
Use 2-3 cross-braces on the drivetrain that go across the entire length of the robot, preferably as far apart as possible. This prevents the chassis from bending over time (not good).
Use standoffs everywhere! Seriously, standoffs are amazing for bracing, and come in handy when you're trying to mount a mechanism to the robot or brace something.
Study how other successful robots mount mechanisms to the robot. There are myriads of reveal videos and robot explanations on YouTube; even looking at robots from previous years can give you ideas on how to design the structure of your robot. Imitate, don't copy.
Easy to learn Can run on any hardware (even chromebooks!) Free (Click for access)
Free (click for access)
Free for students with an education license (click for education access)
The VEX CAD Discord server is a public community server for VEX teams. Server invite:
