Project Overview
STAGE 1D · METHODOLOGY — Planning a subsystem before you ever open a sketch
Cad Starts On Paper
Bad planning shows up as scrap aluminum in March.
- A clear plan turns a 3-day part into 3 hours.
- You can't sketch what you can't describe.
- Every redesign costs build-season time you don't have.
Open with the pain. Ask the room: 'Who's machined a part that didn't fit the robot?' Hands go up. The point of this lesson is to front-load the thinking so the modeling goes fast. We are NOT opening Fusion much today — this is the methodology stage that the whole rest of the unit depends on.
What Every Project Needs
Define four things before sketching: requirements, constraints, packaging, interfaces.
- Requirements: what the subsystem must DO.
- Constraints: rules and physical limits it must obey.
- Packaging: the 3D volume it's allowed to occupy.
- Interfaces: where it bolts to everything else.
These four buckets are the spine of the whole lesson. Write them on the whiteboard and leave them up. Mirrors frcdesign's Project Overview structure. We'll spend one slide on each, then they do it for their own subsystem.
Requirements: What It Does
Write requirements as measurable, testable statements.
- Bad: 'intake grabs the note.'
- Good: 'intake acquires from floor in <0.5s.'
- Include speed, range of motion, capacity, repeatability.
- Tie each to a game task you watched on film.
Stress measurability. 'Fast' is not a requirement; '<0.5 seconds' is. Common mistake: students list wishes, not specs. Have them pull a number from match video or the game manual scoring. These numbers drive motor choice and gear ratios later.
Constraints: The Rulebook
Constraints are hard limits you cannot break.
- Frame perimeter and the starting size limit.
- Extension limit beyond the frame in-match.
- Weight budget: the robot's total mass cap.
- Material/COTS rules from this year's manual.
Constraints come straight from the FRC game manual robot rules (size, weight, extension). Sketch the frame perimeter to scale early — it's the single most useful reference geometry you'll make. Common mistake: forgetting the bumper zone eats into your usable width. The frame perimeter is where the bumpers mount, not the outer edge of the robot.
Packaging: Your Volume
Packaging is the 3D box your subsystem must fit inside.
- Negotiate space with every other subsystem.
- Reserve room for wiring, air lines, and bumpers.
- Leave clearance for hands during maintenance.
- Model it as a simple block before detailing.
Demo making a packaging block: create a component, draw a rectangle, extrude, drop opacity in Appearance. This is the cheapest way to claim territory in the robot. Common mistake: two subsystems claim the same cubic inches. Packaging blocks let the whole team see conflicts in the master assembly before anyone machines anything.
Interfaces: The Handshakes
Interfaces define how it connects to its neighbors.
- Bolt pattern to the frame: 2x1 tube, 1/2in holes.
- Power: NEO or Kraken motor mount face.
- Motion: 1/2in hex shaft, #25 chain or 5mm HTD belt.
- Document mating holes so two people can work parallel.
Interfaces are contracts between teammates. If you agree on the bolt pattern and shaft size up front, two students can model two subsystems at once and they'll still fit. Mention the real standards: 1/2in hex for driven shafts, #25 chain, 5mm HTD 9mm-wide belt, NEO/Kraken bolt circles. This is where Joints come in next lesson — the interface is where you'll place the joint origin.
PLAN THE OUTSIDE BEFORE THE INSIDE
Lock the box, the bolt pattern, and the targets first — then the internals are just filling in a shape you already agreed on.
Structure In Fusion
One subsystem = one top-level Component.
- Right-click > New Component, name it immediately.
- Nest sub-components: arm, gearbox, mounts.
- Bodies live inside components, never loose.
- Activate a component before sketching into it.
Quick Fusion-specific aside. In Fusion, Components are the unit of structure (Onshape calls a workspace a Part Studio — here it's components and bodies). Demo: right-click top of browser > New Component, double-click to activate, then sketch. Common mistake: modeling everything as loose bodies at the top level, then nothing can be jointed or moved. Name as you go — 'Component 14' helps nobody.
User Parameters
Put key dimensions in Modify > Change Parameters.
- Define tubeWidth = 2in, boltSpacing = 1in.
- Reference parameters in sketches and extrudes.
- Change one number, the whole model updates.
- Lets your plan's targets live in the CAD.
Bridge from plan to model. Onshape calls these Variables; in Fusion it's Modify > Change Parameters > User Parameters. Demo adding tubeWidth, then typing 'tubeWidth' into a sketch dimension. The payoff: when a constraint changes mid-season, you edit one parameter instead of re-doing 30 sketches. Encourage them to turn their requirement numbers into parameters.
Insert Cots Parts
Download STEP/F3D files for real hardware.
- REV, WCP, AndyMark, MAXSwerve, McMaster-Carr.
- Insert > Insert McMaster-Carr Component, or upload STEP.
- Model around vendor parts, not from scratch.
- Saves hours and guarantees the holes match.
Onshape has the MKCad library; in Fusion we pull STEP or F3D files from vendor sites and Insert/Upload them. Demo: Insert > McMaster-Carr for a bolt, and mention uploading a MAXSwerve STEP. Key point: never model a motor or swerve module by hand — the vendor file has the exact bolt circle, so your interfaces are correct for free. This is why we nailed interfaces earlier.
Your Task
- Pick one subsystem (intake, arm, climber).
- Write 3 measurable requirements.
- List 3 constraints from the game manual.
- Build a packaging block inside the frame.
- Note your bolt pattern + shaft interface.
- Make a Fusion doc with frame + packaging block.
- Add requirements/constraints as a text note or sketch.
- Add User Parameters for your key sizes.
- Share > Public Link in Fusion.
- Paste the link on AltHub.
This is the deliverable. Walk the room while they pick subsystems — steer pairs away from all choosing the same one. They are NOT modeling internals today; just the box, the interfaces, and the written plan. Check that requirements have numbers. Remind them: Share button is top-right in Fusion, set link to public, paste on AltHub board.
Plan First, Model Second
- Four buckets: requirements, constraints, packaging, interfaces.
- One subsystem = one named Component; drive sizes with User Parameters.
- Insert real COTS files so your interfaces are correct for free.
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.