Building Parts with Features

From 2D to 3D#

Once you have a sketch, you turn it into 3D geometry with features. The most common in FRC are:

• Extrude — push a sketch profile straight out to a depth. A 2x1 in rectangle extruded 24 in becomes a box tube. Extrude can add material (New/Add) or remove it (Remove) to cut pockets and slots.
• Revolve — spin a profile around an axis. Great for shafts, spacers, and pulleys.
• Hole — place properly sized holes (clearance or tapped) with the dedicated Hole feature, which knows standard sizes.
• Fillet / Chamfer — round or bevel edges. Fillets reduce stress concentrations and sharp corners.
• Shell — hollow out a solid to a wall thickness.
• Pattern (linear / circular / mirror) — repeat a feature many times. Essential for the repeating hole patterns on FRC tubes and plates.

The Part Studio: many parts, one place#

A powerful Onshape concept is that a single Part Studio can contain multiple parts that are all designed together in the same space. This enables top-down design: you sketch the overall layout once, then build several parts that all reference that shared layout. Because they share geometry, the parts stay aligned automatically — if you move a mounting hole, every part that referenced it updates.

This is different from older CAD where each part is its own isolated file. In FRC, modeling a gearbox's two side plates plus its standoffs in one Part Studio means they line up perfectly by construction.

A practical build order for a box tube#

1. Sketch and extrude the 2x1 in cross-section to length (use 6061-T6 aluminum dimensions).
2. Sketch the hole pattern on a face: a row of 0.196 in holes on 0.5 in spacing (the common FRC standard, matched to #10 hardware).
3. Use a linear pattern to repeat the hole down the tube.
4. Add fillets/chamfers where needed.

In practice FRC designers automate this with FeatureScripts like Tube Converter (covered later), but you should understand the manual steps first.

Keep the feature tree clean#

• Name your features and parts ('Gearbox Left Plate', not 'Extrude 7'). Future-you and your reviewers will thank you.
• Edit early features by rolling back, rather than piling on fixes at the end.
• Use the right feature for the job — don't fake a hole with an extruded cut when the Hole feature exists.

Why this matters#

Clean, parametric parts are easy to change when (not if) the design evolves mid-season. A messy model that breaks every time you edit it will slow your whole team down. Stage 1A and 1D of FRCDesign.org drill these features in an FRC context.