What changes between prototype and production
Prototype: small batch, hand-stuffed or assembled with limited fixturing, firmware iterating, BOM changing, no per-unit identity.
Production: standardized line setup, firmware version locked per batch, BOM frozen with alternates documented, per-unit traceability, test plan executed against every unit.
The transition is a discrete step, not a gradient. Skipping the transition makes the first production batch chaotic.
NPI gates
NPI (new product introduction) is the structured transition from prototype to production. Typical gates:
Gate 1: Design freeze
- Schematic and PCB layout final
- All EE and ME issues resolved
- BOM with all MPNs filled in
Gate 2: BOM and AVL lock
- Every MPN qualified for production
- Alternates identified and qualified
- Long-lead parts ordered
Gate 3: First article inspection (FAI)
- First panel of boards built on the production line
- Inspected against drawing
- All deviations resolved
Gate 4: Pilot batch
- 50 to 200 units built
- Run through full production process including test
- Yield and defect data collected
Gate 5: Production release
- Pilot results acceptable
- Repeat production cadence agreed
- First production batch scheduled
Skipping any gate means problems show up later when they cost more.
BOM lock
BOM lock means the MPNs are frozen. Changes after lock require a change-order process. The point is not to be inflexible, the point is to make changes traceable so that lot-to-lot variation has a known cause.
Documented alternates are part of the locked BOM. Sourcing can substitute approved alternates without a change order.
Test plan and golden unit
Pilot batch is the test for the test plan. If the test plan does not exist before pilot, the pilot is just an unstructured small build.
Golden unit is a reference unit, calibrated and verified, that the production line uses to compare against. RF golden units are common; sensor golden units exist for some product classes.
Signing keys and provisioning
For products with signed firmware or secure provisioning, the keys and provisioning workflow must be agreed before the first production batch. Key handoff under controlled escrow. Provisioning template documented. PKI infrastructure live (or test PKI for pilot).
Repeat production cadence
After production release, the question is rhythm. Repeat batches typically run on a 4 to 8 week cadence. Forecast the next 3 batches so component sourcing has lead time.
What makes the first production batch work
- All NPI gates passed before scheduling
- BOM locked with alternates documented
- Test plan written and reviewed
- Golden unit available
- Signing keys handed off if applicable
- Production team has met the engineering team
- A clear escalation path for issues found during the run