Sampling and 100% inspection: choosing the right coverage

Classify the characteristics

Identify critical, functional and other drawing requirements through the responsible quality process. Explain the consequence of a nonconforming feature. This provides a basis for discussing which characteristics need screening and which can use the agreed sampling or approval method.

Define what full inspection means

Specify the feature, method and handling for every-piece screening. A camera check of length does not mean every thread, material property and internal surface has been verified. Destructive tests also cannot be applied to each delivered component in the same way as a non-destructive dimensional check.

Agree sampling as a documented plan

Where sampling is used, define the applicable procedure and order-specific acceptance requirements. Avoid an informal percentage with no lot definition or disposition rule. The plan should explain what happens when a sampled result fails and how the affected material is controlled.

Keep process control and acceptance connected

Inspection is more effective when supported by stable manufacturing and traceable records. Define reference checks, measurement capability and lot handling as appropriate. Additional inspection should address an identified requirement rather than simply adding a broad label that neither side can demonstrate.

Specification example

A buyer may request every-piece optical length screening while using separate thread-gauge sampling and material documentation. Writing each requirement explicitly is clearer than calling the entire order fully inspected.

RFQ checklist

• Characteristic classification
• Method and actual coverage
• Lot definition and sampling rules
• Failure disposition
• Records and traceability