Subsystem Summary
Stage 1E · Subsystems — wrapping up the subsystem workflow and bridging to full Stage 2 mechanisms in Fusion 360
The Stage 1 Journey
You began Stage 1 with empty sketches.
- Learned sketching, constraints, and dimensions.
- Built bodies with extrude, revolve, and pattern.
- Organized geometry into named Components.
- Now: a clean, jointed subsystem assembly.
Open the timeline of their own work if you saved early files. Remind them how far they've come: in 1A they couldn't fully constrain a rectangle, now they're assembling multi-part mechanisms. Set a celebratory but focused tone. The point of this slide is reflection before we bridge to Stage 2.
Sketch-Driven Design
- Start every part from a fully-defined sketch.
- Black sketch = fully constrained, no surprises.
- Drive key dims from User Parameters.
- Modify > Change Parameters edits the whole model.
Reinforce: under-defined sketches (blue lines) are the #1 source of broken models. Demo dragging a blue sketch entity to show it moving, then add a constraint to lock it. Show that editing a User Parameter ripples through the whole part — this is the Fusion equivalent of Onshape Variables.
Components, Not Just Bodies
Every real part = its own Component.
- Bodies are geometry; Components are parts.
- Components get joints, motion, and BOM rows.
- Right-click body > Create Components from Bodies.
This is the biggest mental shift from sketching. A body is just shaped material; a Component is a part that can move, mate, and appear in the Bill of Materials. Common mistake: students model everything as bodies in one component, then can't joint anything. Show the browser tree and the activation dot.
Joints Drive Motion
- Rigid joint: bolt two parts solid together.
- Revolute joint: a shaft or arm that spins.
- Slider joint: an elevator carriage or linear slide.
- Assemble > Joint, pick two snap points.
This is the Fusion equivalent of Onshape Mates. Map it plainly: Rigid = Fastened Mate, Revolute = Revolute Mate, Slider = Slider Mate. Demo capturing the joint origin by hovering a hole edge to snap to its center. Common mistake: jointing bodies instead of components — joints need components.
Use Real Cots Parts
- Don't model bearings or motors from scratch.
- Download STEP/F3D from REV, WCP, AndyMark.
- Insert > Insert Derive or upload to your project.
- Grab fasteners as STEP from McMaster-Carr.
This replaces Onshape's MKCad library. Vendors publish CAD: pull the exact NEO, Kraken X60, or MAXSwerve model rather than guessing dimensions. McMaster-Carr has a 'Save CAD' button — choose STEP. Tip: insert COTS parts FIRST, then design brackets around them so your hole patterns actually match.
A SUBSYSTEM IS PARTS THAT MOVE TOGETHER
Components define the parts, joints define how they move — that combination is the whole game in robot CAD.
Design To The Standards
- Shafts: 1/2 in hex or 3/8 in hex.
- Structure: 2x1 and 1x1 aluminum tube.
- Gears: 20 DP, hubs on 1/2 in hex.
- Power transfer: #25 chain or 5mm HTD belt.
FRC has de facto standards. Designing to them means COTS parts just fit. Stress hex over round shaft: hex transmits torque without keys or set-screw slip. 20DP is the team standard tooth size. Tell them: if your bore isn't 1/2 hex, your gear probably won't mount to anything.
Keep It Organized
Name every component as you create it.
- Rename features in the timeline too.
- Capture design intent with parameters.
- Save versions often — Fusion keeps history.
Unnamed 'Component1, Component2, Body3' assemblies become unmaintainable fast, especially when a teammate opens your file. Two-minute habit now saves hours later. Show right-click > Rename in both the browser and the timeline. Mention Fusion's cloud version history as the safety net.
Can You Do These?
- Model a part from a defined sketch
- Convert bodies into named components
- Add rigid, revolute, slider joints
- Insert a COTS STEP file
- 1A-1B: sketching & constraints
- 1C: extrude / revolve / pattern
- 1D: components & joints
- Vendor CAD: REV / WCP downloads
Have students honestly self-assess against the left column. Anyone shaky on a row should revisit the listed lesson before Stage 2. Don't shame gaps — this is exactly when to fill them. You might do a quick thumbs-up/thumbs-down poll per row to see where the class stands.
Your Task
- Design a single-joint subsystem
- One moving part on a 1/2 in hex shaft
- Use a revolute joint for the motion
- Include one real COTS part (bearing/gear)
- Verify sketches fully defined (black)
- Name all components & joints
- Fusion > Share > Public Link
- Paste the link on AltHub
Scope this tight: a shaft in two bearing-bored plates with one gear, jointed to spin. That's enough to exercise every Stage 1 skill. Walk the room checking for blue sketches and body-vs-component joint mistakes. Collect public Fusion links on AltHub so you can review motion before next class.
Bridge To Stage 2
Stage 2 = full mechanisms, not single joints.
- Build an intake, elevator, or arm.
- Chain multiple joints into one system.
- Apply gear ratios and motor selection.
Build excitement: Stage 1 was the alphabet, Stage 2 writes sentences. They'll combine many components and joints into a working subsystem like a real robot mechanism. Preview that motor choice (NEO vs Kraken) and gear ratios start mattering. Tease the specific first Stage 2 mechanism you'll build.
You Can Now Build A Real Subsystem
- Sketches define parts; components make them real.
- Joints turn parts into motion.
- COTS + FRC standards keep it buildable.
Your Task
- Model what this lesson covers in Fusion 360.
- Use the AltSkripts tools where they apply.
- Save it with a clear name.
- In Fusion: Share → Public Link → Copy.
- Paste the link below.
- A coach reviews it in AltHub.