This year I’m the Cad Lead on my team. Build season is approaching with frightening speed and I do not feel like I am prepared. I’m one of the most experienced cadders on our team, but although I’ve designed individual parts, 3d printing components, and made alterations to pre-designed mechanisms, I have little to no experience in actually designing and cadding a full mechanism from scratch like we will have to do come build season. Plans have been made with the mentors of my team on how to prepare the team as a whole for the design portion of build season, but I want to know how I can prepare myself for it. What can I do to practice design? What are the most essential design skills I should get a grasp on? How do I take something from a basic design concept to a cadded design? Is there any essential information I need to know about the design process?
Back when @AdamHeard was on 973 he put together a great series of CAD tutorial videos. Covered a bunch of techniques and best practices from basic to advanced levels. Highly recommend everyone check it out.
Sort of a more general take on design but maybe it will offer some help.
Two things I typically think of as the most important factors when creating a design are the material/stock you are going to make that thing out of and the manufacturing process you are going to use to do so. There are only so many available sizes of tubing, sheet goods, fasteners, bearings, gears pulleys, etc. Understanding this as well as your own teams manufacturing capabilities, whether it be 3d printing, CNC, manual machining/drilling, or whatever else, is huge. Notice that these two ideas alone already narrow down so many design decisions and they are typically a decent place to start once you kind of know what you are trying to accomplish.
Some more CAD specific advice would be to start with some generalized sketches. These could be 2d or 3d by hand or in CAD but they will help you conceptualize what you are trying to make. This is especially helpful in any mechanism with complicated linkages or unique motions. From there you can more easily see what each individual part has to look like within the overall assembly.
Just out of curiosity, what Software are you using?
If you want to self train & you’re using Onshape, I recommend 3847’s curriculum (search for it) + everything Onshape4FRC.com covers. 3847’s design walkthroughs in particular teach a lot. The best teacher is experience. Maybe try the CAD-a-thon coming up. Good dry run. You are not alone… There are several students on our team and many teams in a similar spot. Good luck!
I started out using Fusion but my team has recently switched over to OnShape.
Best way? Design something!
All of the suggestions here are great. Definitely look through tutorials and things. But if you want to really practice, design something. Your team probably has a go-to style for making parts based on how they get them made. If you have a waterjet sponsor, design it so the complex parts can be waterjet cut. If you primarily cut 2x1 tube on a router, then design a few mechanisms that way. Just make sure you think through how those items will physically get made. It’s great to try to interface COTS parts with the things you are making.
Some fun suggestions on parts to design:
West Coast Drive
Elevator
Ball intake
Shooter
Remember, you are practicing design - not making season decisions. Just because you designed a WCD, you still may be better off with a KOP chassis. Right now you are designing for the experience (although it’s sometimes fun to prototype these designs if you have the resources).
I know you said you are covered on this … but this may still help you personally prepare →
One concept that my team employed is having a set of standards for CADding. This includes design parameters, procedures, and industry practices. A very straightforward example of this application is making sure all of your bolt patterns line up. Being all on one page (both intra and interdepartmental) is an extreme time saver in the build season. You will learn once you get some exposure (if not already) to the vast amount of software and procedures large companies have in place for project management. This can range from keeping track of design conditions to project-gate-and-gantt stuff. Making sure all files are updated and backed up, and revisions are kept track of - lots of things. There is certainly no shortage of employee/employer opinions on some of these protocols and whether or not they are time wasting - but I’ll let you decide.
Anyways.
An example of our Team’s old CAD standards are found attached.
As far as it goes for you as an individual, what I like to do is literally think about it all the time. When you sit down in your car - sure you could think about how combustion works in the ICE (assuming you drive a car with an ICE lol). But try thinking about the seat moving mechanism… why was it manufactured the way it was? Where is the spring that pushes the chair forward? How does the chair move and not fall out of the rails or slots or whatever? If there are hard stops…how did the chair get in there in the first place? How was it built? Lots of things all around us that were engineered at some point - some indeed better than others.
So, practicing CAD can be easy - knowing what buttons what do - how to click them.
Design is hard. It’s learned through experience and can always be improved. Out in the real world, I like to think as engineers and innovators, you always have to be learning to keep up with technology and stay competitive. Thinking from perspectives of the manufacturer and customer. Considering design intent - the order essentially in which you click those buttons in CAD 
.
Design is something that comes with experience - stay up to date on technology and products that are released into the FIRST industry. It can be fun to CAD mechanisms for things other than robots too… Christmas is coming up … maybe use gift ideas as food for thought.
If your team keeps old robots… try to CAD that robot if you have an incomplete file for it. Thats how I learned a lot about CAD and design. I would sit down, CAD pre-existing, past robots, and learn what we could have done better as I go. I CADded down to the duct tape. Anyways, have fun with it. Lexeo has some good suggestions. And their last point is incredibly important.
I like to say fail fast - (it sounds like something Henry Ford would have said) if you are working on an idea, and it isn’t going the way you wanted it to… move on! Don’t exhaust your resources and waste your time because you seemed to have put so much effort into it. I’m trying to explain this without being a debbie downer. There is a distinguishable difference between patient, hard work, and time-wasting developmental work. I’ll give an example:
In 2020, my team had a “spindexer” - a rotating drum meant to deposit power cells into the chamber on a defined frequency. We had trouble moving the power cells off of the drum, and into the chamber, so we tried to use pneumatics for the first time (at least with our current team members, it was their first), and use a “kicking” mechanism. It didn’t work, and competition was approaching. Instead of trying to make this continue to work, we moved onto a track mechanism, removing the spindexer entirely. So, although we never achieved our vision of the “perfect” mechanism, the track ended up working. But the most important thing was that we still learned how pneumatics worked and were excited to try new projects with them. That is what I mean when I say fail fast.
Sorry, I get excited when talking about design. So, try CADding some fun things. Ideas:
- Belt driven power cell intake
- 2019 Climber
- Clock
- Metronome
Happy CADding, and good luck in the upcoming build season. Remember to try and learn as much as you can!
Best,
Noah
Design_Standards_113022.pdf (119.3 KB)
I one up this! I also recommend checking out the “recommended reading” section of 3847s, it has a collection of the best design resources from other teams in one place. If you’re looking to design, I highly recommend the NASA RAP design guide.
Thank you for the praise. Our training information can be found at Training.Spectrum3847.org
And you can find all the video on our YouTube page.
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