FTCDesignDesign Guide

CAD Best Practices

Five articles to read in order. The goal: keep loading times low and stay organized so changes stay easy.

1. Document setup

An Onshape document holds tabs. Tabs hold Part Studios, Assemblies, and Drawings. Default impulse: pile parts into one Part Studio. Don't.

What goes in the root document:

  • One Part Studio per subsystem.
  • One Assembly that pulls subsystems into the full robot.
  • Drawings only for parts fabricated outside Onshape.

Name every tab. Drivetrain beats Part Studio 4.

2. Sub-document setup

Once a subsystem grows past about forty parts, move it to its own document and link it back. Smaller documents load faster and unblock teammates working in parallel.

When to split

If regeneration takes more than 5–10 seconds, or if two people are blocked editing the same Part Studio, split.

3. Layout sketches

A layout sketch is a master sketch that drives downstream parts. Edit one set of dimensions, the whole subsystem updates.

What goes in:

  • Chassis outline.
  • Motor positions.
  • Wheel positions and contact points.
  • Pivot axes for any moving subsystems.

4. Part studio practices

One subsystem per Part Studio. Variables, not magic numbers.

For any robot, define on day one: #chassisLength, #chassisWidth, #wheelDiameter, #frameThickness.

Rename features as you create them. Default Onshape names (Sketch 4, Extrude 7) cost minutes later.

5. Assembly practices

The top-level Assembly is where subsystems meet. Three rules:

  1. Use mate connectors on every part you'll mate to more than once.
  2. Prefer Fastened mates. Reach for Revolute or Slider only when something actually moves.
  3. Group related parts to keep the Instances panel readable.