Why CAD before you cut
What CAD saves you, why Onshape specifically, and how to set up a team workspace properly.
By the end you can
- Explain what designing in CAD saves a team in time and material
- Set up an Onshape account and a shared team document
- Describe how Onshape's version history replaces emailing files around
You can build an FTC robot without CAD. Plenty of teams do, and some of them do well. But they spend their season doing something specific: cutting a part, discovering it does not fit, and cutting it again.
What CAD actually buys you
- Fit checking
- You find out that the motor mount interferes with the drivetrain rail on screen in ten seconds, not on the workbench after cutting the part.
- Iteration speed
- Changing a dimension in CAD takes a moment. Changing it in aluminium takes an evening and a new piece of stock.
- Shared understanding
- Your whole team can look at the same model and agree on what is being built, instead of arguing from three different mental pictures.
- Judging evidence
- A documented CAD model with a visible iteration history is direct evidence of an engineering design process — exactly what judges are looking for.
The real cost of not using CAD
It is rarely one dramatic failure. It is a steady drip of small ones — a hole pattern that is 4 mm off, a bracket that hits a wheel at full rotation, a lift that cannot reach because nobody checked the geometry. Each costs an evening. Over a season it adds up to weeks.
Why Onshape
Onshape is free for FIRST teams, runs entirely in a browser, and works on Chromebooks. For a school-based team with mixed hardware, that combination is hard to beat.
The feature that matters most is less obvious: Onshape has real version control built in. There are no files to email around. Everyone works in the same document, changes are tracked with who made them and when, and you can branch to try a risky redesign without breaking the working version.
The problem this solves
Every team that uses file-based CAD eventually ends up with robot_v4_FINAL_final2_ACTUALFINAL.step and no idea which one the build team is working from. Onshape makes that failure mode impossible.
Setting up properly
Do this once, at the start of the season, and it pays for itself all year.
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Get the FIRST education plan. Sign up at onshape.com with the education/FIRST option rather than the free hobbyist tier — the hobbyist tier makes all your documents public and limits private storage.
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Create one team document per major assembly. A common structure is one document for the robot assembly, with separate Part Studios inside it for the drivetrain, each mechanism, and shared hardware.
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Invite the whole build team. Everyone gets edit access. Onshape tracks who changed what, so shared access is safe.
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Import the FTC part libraries. goBILDA, REV, and other suppliers publish public Onshape documents containing their parts. You can link these directly rather than modelling a motor from scratch.
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Agree on units before anyone models anything. Mixing millimetres and inches inside one assembly is a genuinely painful problem to unpick later. Pick one and write it in the document description.
Pick millimetres
Most FTC structural systems — goBILDA especially — are metric, and hole patterns are specified in millimetres. Unless your team is committed to an imperial system, millimetres will cause fewer conversion mistakes.
The one habit that separates good CAD from bad
Fully define every sketch.
In Onshape, an under-defined sketch shows in blue: its geometry can still move. A fully defined sketch shows in black — every point is locked down by a dimension or a constraint.
Under-defined sketches feel faster because you skip the dimensioning. They cost you later, because:
- Changing one dimension makes unrelated geometry drift unpredictably.
- Two people editing the same part get different results.
- You cannot trust the model to match what you will manufacture.
This is the first thing a design review looks at
When anyone reviews your work — a teammate, a mentor, or a judge at a meet — sketch definition is the first thing they look at, because it is the strongest single signal of whether a model is trustworthy.
Get in the habit now, while your sketches are simple. It is much harder to adopt on a 40-feature part.
Check yourself
You open a teammate's part and the sketch geometry is blue rather than black. What does that tell you?
Next
Account set up and the golden rule established. The next lesson gets you sketching — constraints, dimensions, and your first fully defined profile.