CAD in FRC Robot Design

Technical CAD
#1

Hello everyone!

My name is Kavin (you may recognize me from the InspireNC CAD Challenge) and I’m currently part of the Full Moon Robotics Ri3D team. You can check out our livestream on twitch!

In our first year doing Ri3D last year, given the time crunch, we ended up not developing CAD models for our robot. However, we received requests from our viewers that you all would like to see CAD models and files for our robot. That’s why, this year, we have decided to CAD our robot as we build it, in an effort to demonstrate the power of CAD in the design process, as well as to provide a resource for teams who are interested in using CAD.

You can check out a quick interview I gave on my progress, as well as the benefits of CAD with this video!

I wanted to ask you all - what is the best way to integrate CAD into the design process? Should you completely CAD the robot before you begin construction, or is a hybrid approach (building and CADing concurrently) more effective in FRC?

I can’t wait to hear what you all think, and I’ll also keep you all updated with our CAD progress in this thread!

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#2

We use CAD from the very start. Construction is usually in parallel but slightly delayed so our process probably matches the hybrid approach you mention. During design we follow this process.

When debating archetypes we sketch ideas by hand and then generate “crayola CADs” and layout sketches.

Crayola CADs are 3d blocked out areas that give a general sense of where mechanisms will go. They help you evaluate how everything will fit together and get a general sense of how it will all look.

Layout sketches are 2-d sketches that serve a similar purpose to the crayola cads. They are often used from a side profile of the robot and are especially useful to think about the height constraints and needs of the robot.

This is an example layout sketch for our 2020 climber. The left section makes sure it will fit under the mechanism's max desired height while down and the right makes sure it can reach the bar when it is at it's highest postition.

2020 climber layout sketch
2020 climber layout sketch299×505 27.7 KB

JVN talks about the two here: Prototyping in CAD — JVN Blog

Pearadox talks about crayola cad under “space allocation” section 3.4 on page 11 of their CAD and Drawing Standards. CAD and Drawing Standards

From there once we have chosen an archetype, the crayola CAD is used to define the room each designer has for their mechanism(s). Prototyping, layout sketches and preliminary designs are used to refine the crayola CAD. If they need more room than the crayola CAD allows, they update the crayola CAD to match how much extra room they will use. If the needed room will interfere with another mechanism they have to figure out how to solve the problems with the design lead of the other mechanism.

From there each mechanism is designed, reviewed and machined. Once it is assembled it is tested and iterated. The second and third versions are the ones that make it on the robot.

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#3

I would love to see a series of videos showing how a team designed their robot from start to finish.

It’s one thing to be comfortable with the basics of a CAD system, but an entirely different and more complex skill to design a full robot, subsystems and all.

Personally, I am struggling as I attempt to take that leap… I am nowhere close to being able to design a system of moving parts that integrate and function as a robot.

Any resources you all could point me to?

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#4

There is no replacement for actually doing it, many times, and getting feedback from others.

For some resources on design thinking… I’ll do a little bit of a self plug for my tutorials, which while they also deal with the specifics of modelling, are in may cases as much about the thought process and design as a whole.

That being said… thanks for the ideas, sounds like a fun set of videos to make focusing on the entire process, if only someone would go and make them :slight_smile:

As a team develops competency in CAD, their relationship with it and how they use it over a season will naturally develop. Like in almost all areas of everything, it’s a poor choice to claim that there is a universal best approach. A sensible progression is to structure your team to progressively make more use of CAD in the areas that will have the greatest impact. This may mean starting with small parts and concept sketches, then progressing to more detailed designs when the team obtains a CNC. It may mean leaping straight in because the team has access to all sorts of fancy tools. It may mean no CAD at all for a while.

CAD is ultimately a tool that can be used to achieve the aims of the team. It is silly to treat a tool like the aim in itself.

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#5

A sensible progression is to structure your team to progressively make more use of CAD in the areas that will have the greatest impact.
CAD is ultimately a tool that can be used to achieve the aims of the team. It is silly to treat a tool like the aim in itself.

I completely agree, everyone has their own way to integrate CAD into the process that works best for them. Perhaps I should have rephrased the question to be “how does your team integrate CAD into the design process” :slight_smile: .

I think one of the best explanations as to how the approach to CAD changes based upon the circumstance is actually in your video reviewing a submission from the INC CAD Challenge!

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#6

^This

I know some teams will do most of their prototyping with 8020 and janky plywood setups, and then CAD their final robot assembly, while others (like us) spend more time early in the process playing with high-level layout sketches and crayola assemblies. The “right” way is whatever works for you

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#7

FRC 832 designs in CAD first, then builds the part to spec. Unlike another team I know, that builds a robot and has the CAD subteam running after the robot with calipers to document what was built.

All it takes is having essentially everyone on the team very proficient in CAD. Not trivial but that’s what it takes. Gotta be part of the culture.