Method Summary

Frame this as the payoff slide for Stage 1. Everything they learned about layout sketches, components, and joints comes together into one repeatable recipe. Stress that top-down is how competitive FRC teams (118, 254, 1678) actually CAD — you define intent once at the top and let it flow down. Bottom-up modeling (building loose parts and gluing them together) is what beginners do and what causes rework.

Demo creating the layout sketch on the origin XY plane. Show that a black sketch is fully constrained and a blue one is not — chase blue lines until everything is black. Open Modify > Change Parameters and show wheelbase and trackwidth as User Parameters, then change one number and watch the sketch update. Common mistake: leaving the sketch under-defined, so geometry drifts later.

This is THE Fusion-specific habit to drill. In Onshape you'd use Part Studios; in Fusion you make Components. A Component can be joined, given mass, and inserted into other designs — a loose Body cannot. Show activating a component (the radio dot) so new sketches and features land inside it. Common mistake: modeling everything as bodies in the top level, then having no joints possible later.

Show Sketch > Project/Include > Project (shortcut P) to pull the wheelbase lines from the layout sketch into a part sketch. Projected geometry shows purple and updates when the parent changes — this is the core of top-down. Common mistake: students re-draw and re-dimension the same line in every part, then it all goes out of sync when they edit one. Emphasize: single source of truth.

Now turn the skeleton into real structure. FRC standard is 2x1 inch aluminum tube, usually 1/8 inch wall, with holes on the WCP/AndyMark grid (0.5 in spacing). Demo Extrude from a projected profile. Keep the timeline clean — small, named features are easy to fix. Common mistake: monster sketches with 40 constraints that nobody can edit later.

Fusion translation of MKCad: there's no built-in FRC library, so you download STEP or F3D files from vendors and Insert them. Insert > Insert McMaster-Carr pulls bolts and bearings straight in. For swerve, download the REV MAXSwerve or WCP module STEP from the vendor site and Insert > Insert Mesh/Derive. Common mistake: students try to model a NEO or a gearbox by hand — never do that, it wastes hours and is less accurate.

Fusion translation of Onshape Mates: use Assemble > Joint. Rigid = bolted-solid (most structure). Revolute = one rotation axis (wheels on a 1/2 inch hex shaft, arm pivots). Slider = linear travel (elevator carriage). Pick the joint origin carefully — snap to a hole center or hex axis. Common mistake: rigid-joining everything, then nothing spins; or using As-Built Joint and losing the ability to motion-test.

Quick rapid-fire review of the traps. The activate-component one is the single most common — students model a sketch and it lands in the wrong component or the top level. Show the browser to confirm where new geometry goes. Redundant constraints throw the over-defined warning; teach them to delete a dimension rather than add a relation on top.