Fast Functional Prototype Checklist: What to Lock Before the Build

A rushed functional prototype often creates more confusion than it resolves when nobody agreed in advance what it needed to prove. This checklist helps hardware teams get a useful answer from a fast build instead of just a fast one.

Decide what the prototype must prove

A functional prototype built to answer one specific question moves faster than one trying to validate everything at once. Name the single riskiest assumption before deciding the build method.

• The one mechanism, fit or function this build must prove.
• What can still be wrong elsewhere without invalidating the test.
• Who needs to see the result and what decision it unlocks.

Lock the inputs that would waste a rebuild

Overall envelope, critical interfaces and any electronics placement should be locked before the build starts, since changing these after fabrication usually means starting over.

• Outer envelope and mounting or interface points.
• Electronics or mechanical placement that drives the structure.
• Material or process substitution limits for the fast build.

Choose a test method that matches the question

The fastest build is wasted if the test method cannot actually answer the question it was built for. Match the fabrication process to what needs to be measured or felt.

• 3D printing for fit and rough ergonomics.
• CNC or urethane casting when surface finish or stiffness matters.
• What data or feedback format the test needs to produce.