Even with a qualified MIM supplier, incoming inspection provides the final verification that the parts you received meet your specification. Here is a practical system.
Incoming inspection checklist:| Check Item | Method | Acceptance Criteria | Sampling |
|---|---|---|---|
| Certificate of Analysis (CoA) | Document review | Chemistry, density, mechanical properties per spec | 100% of shipments |
| Dimensional inspection (critical features) | CMM or vision | Per drawing tolerance, CpK ≥ 1.33 | Per AQL or sample plan |
| Dimensional inspection (general features) | Calipers, gauges | Per drawing tolerance | AQL 1.0 |
| Surface finish | Profilometer or visual standard | Ra per drawing requirement | Sample per batch |
| Visual (flash, gate vestige, surface defects) | Visual under controlled lighting | Per acceptance standard | AQL 0.65 or 100% |
| Density (verification) | Archimedes per ASTM B311 | > 95% of theoretical | 1 part per sintering batch |
| Packaging and labeling | Visual | Correct quantity, labels match PO | 100% of boxes |
| Certificate of Conformance | Document review | Stated conformance to PO requirements | 100% of shipments |
| Application | Recommended AQL | sample size code |
|---|---|---|
| Non-critical commercial parts | AQL 1.0 | Per ANSI/ASQ Z1.4 |
| General automotive | AQL 0.65 | Per customer-approved plan |
| Safety-critical automotive | AQL 0.1 or 100% | Per control plan |
| Medical implant | 100% critical features | Per device master record |
- CMM or vision measurement system (±0.005 mm accuracy)
- Digital calipers and micrometers
- Hardness tester (Rockwell or Vickers)
- Precision balance (0.0001 g) for density measurement
- Surface roughness profilometer
- Comparison standards for visual acceptance
At minimum: verify CoA (chemistry, density, mechanicals), inspect critical dimensions (per CpK ≥ 1.33 requirement), check visual quality (flash, gate vestige, surface defects per acceptance standard), verify density (Archimedes method), and confirm correct quantity and labeling. For automotive and medical parts, add full dimensional report verification and material certification review per PPAP requirements.