Computer-aided design

Introduction

Computer-aided design (CAD) stands for computer aided design: making a 3d model of your robot using special computer software.

Tip

CAD is not necessary in FTC to build a successful robot.

Many successful teams didn’t CAD their robot at all. Other successful teams only made parts of their robot in CAD. Still other teams fully designed their robot in CAD.

So, what’s the point of CAD, then? It is encouraged that new teams try their hand at CAD, especially if you have a mentor or parent who is experienced in such an area. CAD is beneficial for multiple reasons.

  1. CAD solves a lot of preventable headaches, such as spacing issues. Thus, it will save time when you discover problems in CAD that you can remediate before you build your robot.

  2. CAD is a professional tool that is used in many STEM fields. Having CAD knowledge and skills will be beneficial in your future career, should you study and work in those fields.

  3. If you desire to create 3D-printed or machined parts, CAD will be necessary to do so.

However, CAD is not the magic genie that will guarantee you success in FTC. When used properly, it is a great tool to aid teams in building their robot. Keep in mind, though, that many teams have had success without CAD.

Starting off, choose a CAD program and learn it as well as possible. It may be a good idea to spend a few weeks just finding objects lying around, sit down with a ruler or calipers, and make a quick CAD model. A good way to test accuracy is to choose a solid object made up of one known material. Weigh the object and make the model in CAD, apply that material to it, and see what the weight difference is. This is a good way to test how accurate the CAD model is to the real part. It really doesn’t matter what object it is - just find something and make it to the best of your abilities. There are also tons of videos on YouTube; a good one is TFI who makes detailed tutorials for Autodesk Inventor.

Overview of CAD Programs

There are many possible CAD programs that teams can learn, all of which can be downloaded for free under a student or FTC team license. You’ll have to do a bit of research here, as the requirements for free copies vary based on the program. Here are a couple suggestions to consider:

SolidWorks

An industry standard CAD package made by Dassault Systemes. It’s as fully featured as CAD software gets, including great simulation features and a very robust assembly environment. It’s used widely in industry and is also the program of choice for most college-level engineering classes.

However, it isn’t available for Mac users, and you’ll need a pretty beefy computer to run it (16GB RAM is standard). SolidWorks also comes with a solid simulation program if you wish to test the structural properties of your robot or a custom-designed part.

If you have mentors or team members with previous experience in SolidWorks or an engineering class at your school that teaches SolidWorks, it will be your best choice.

Inventor

Autodesk’s industrial CAD offering. It offers many similar features to SolidWorks, but has a different UI and three distinct assembly modes.

While it’s used by many companies in the industry, it doesn’t appear in very many college curriculums. Inventor is generally the second choice for companies who don’t use SolidWorks but instead are based around the Autodesk universe.

Inventor is also not available for Mac, but it may run better on lower-spec PCs.

If you have mentors or team members with previous experience in Inventor or an engineering class at your school that teaches Inventor, it will be your best choice.

Onshape

A fully-featured CAD package, but it runs entirely in the cloud. It can run on any computer (even Chromebooks!) and has iOS, iPadOS, and Android apps as well.

It has all of the same core features as SolidWorks and Inventor, as well as the best collaboration workflow in the industry - many people call it “the Google Docs of CAD.” Onshape allows multiple people to work on the same document at the same time, and allows users to “follow” each other and see what’s on another user’s screen.

OnShape also has FeatureScript, a programming language where you can write custom features. The community has created a lot of very useful FeatureScripts already which you can use completely for free.

Onshape also has a comprehensive tutorial system (https://learn.onshape.com) that will not only teach you how to use their software, but how to approach design problems.

If you’re just starting out with CAD, or you don’t have access to powerful computers, Onshape is the software for you.

Fusion 360

A cloud-based all-in-one CAD/CAM package, also made by Autodesk. Fusion 360 is cross platform compatible, although it doesn’t run very well on low-spec computers.

It has a powerful CAM environment for machining your parts, and it has intuitive and easy cloud rendering that gives the heavy lifting to Autodesk’s servers. To maintain a simpler UI, Fusion skips out on a lot of the more advanced features found in SolidWorks and Inventor, although this isn’t really much of a problem.

However, a more noteworthy difference is that Fusion ignores every single industry standard, creating its own structure and organizational system. Beyond simple sketches and extrude features, Fusion’s modeling and assembly system is unique and not compatible with any other CAD software, making it hard to switch away from Fusion.

Because of this, if you aren’t careful, Fusion’s file hierarchy can actively encourage bad design habits and discourages reusability by allowing users to create new parts without designing them individually first.

If one is careful to follow good design practices, Fusion is a solid option.

Creo (formerly known as Pro/E)

A family of CAD/CAM applications developed by PTC (Parametric Technology Corporation). Creo parametric is the main CAD package that includes robust assembly and part modeling similar to Solidworks.

The main advantage of Creo compared to other CAD software is the complex part relations and constraints, however, most new users find this aspect difficult to grasp completely. The Creo package includes an integrated local rendering engine and thorough simulation system. The rendering engine can be used to create photo-realistic renders of anything between single-part simple to multi-component complex designs. Design enhancements can be directly integrated into parts from materials/geometry simulations in Creo Simulate.

Creo has many features, but the general 80-20 rule applies - 20% of the features will create 80% of the designs. The Creo package also includes a version based file sharing system called Windchill which most professional companies use, but for FTC purposes Grabcad will suffice.

Learning Creo can be more of a challenge than other CAD software, because of the limited available tutorials online in addition to the complex relations and constraints structure. Our recommendation is to learn Creo from someone who already has experience with the software.

College-level engineering classes as well as numerous companies in the automotive, aerospace and consumer industry use Creo. Since Creo makes use of Windows OS file system it will not run on Mac. However, a Windows emulator can be installed to run Creo on Mac.

Getting Parts

All vendors (REV, goBILDA, Actobotics, AndyMark, Tetrix) provide 3d models of the parts they sell in STEP format, which can be imported by any of the CAD programs above. Some vendors also offer repositories or zip files containing STEP file of all the models they sell. For example, REV Robotics offers such a repository on their Technical Resources page.

For more public repositories of FTC parts, check Useful Resources section in the Appendix.

File sharing

Teams often have multiple members working on CAD models, and thus require a file sharing system for ensuring that each person has up-to-date files. Some recommendations include GrabCAD, Box, Google Drive, or Dropbox.

It is also a good idea that one team member work on the model at a time to prevent confusion.