- Engineering samples validate design; pilot lots validate the production process.
- Freeze drawing, BOM, finish and CTQs before FAI approval.
- Cpk and AQL require valid statistical assumptions and risk-based targets.
- Re-evaluate changes to material, tooling, process and subcontractor.
Values in this guide are practical starting points for RFQ, DFM and prototype validation. They do not replace load calculations, regulations, material certificates, qualified procedures or approved production drawings.
Gate 1: DFM and Risk Register
Close material availability, special tolerance, forming/welding access, finish, inspection and packing issues. For each CTQ, record potential failure, control and owner. Convert quotation assumptions into drawing, specification or purchase-order requirements.
Gate 2: Engineering Prototype
The engineering sample validates geometry and process route; it may not use production takt time, but material, thickness and critical processes cannot be casually substituted. Produce a dimensional report, assembly record, functional/load results, cosmetic issues and change list. Feedback should state measured value, requirement, location, image and disposition—not merely “does not fit.”
Gate 3: Design Freeze and First Article
The approval pack includes controlled drawing/model, BOM, certificate requirements, finish sample, CTQ list, inspection method and packing instruction. First-article reporting covers all drawing features or the agreed scope, using calibrated gauges. A later change to material, tooling, program, supplier or finish triggers proportionate revalidation.
Gate 4: Pilot Lot and Capability
A pilot lot should use production equipment, fixtures, people, finishing and packing. For stable processes, calculate Cp/Cpk on key variables. Cpk≥1.33 is a common discussion point and ≥1.67 may be requested for critical features, but sample size, distribution and stability assumptions must be valid. A few passing values do not prove capability; use enhanced first-lot inspection when data are limited.
Gate 5: Production Inspection and Release
Define incoming, first-off, in-process, last-off and final checks in a control plan. Attribute/cosmetic inspection may use ISO 2859-1:2026. Commercial projects often set zero acceptance plus tightened or 100% inspection for critical defects, then discuss AQL 1.0/2.5 for major/minor defects. These are not universal defaults and must follow risk and contract. AQL indexes lot-acceptance sampling; it is not permission to manufacture that percentage defective.
Gate 6: Packing Validation and Change Control
Packaging validation should simulate stacking, vibration, drop, moisture and long-haul abrasion risk, then inspect post-test finish and dimensions. Retain approved/limit samples and packing photos. Use PCN/ECN after launch: evaluate changes to grade, thickness, tooling, route, subcontractor or critical parameters before implementation.
RELEASE CONDITIONS
- All technical issues closed; drawing and BOM on one revision
- FAI, assembly, function and appearance approved
- Production tooling, program and gauges validated
- CTQ control plan and sampling plan signed
- Packing and labeling passed distribution-risk validation
- Change, concession and traceability processes defined