The difference between zero defect and full inspection


As everyone knows, if the sampling in TS or the inspection according to GB2828 is not qualified, it must meet zero defects, that is, it must be inspected completely, but if the inspection is performed at the beginning, is it a zero defect, that is, zero defect and inspection Whether the meanings are equal in the acceptance criteria.


1. Zero defect is actually an acceptance criterion; full inspection is just an inspection scheme, and the two should be different.

2. Zero defect means that the probability of non-conforming product is 0%, which is a statistical concept. Full inspection refers to 100% inspection. After the full inspection process, there may still be non-conforming products. Refers to sampling inspection based on the AC = 0 decision principle of the sampling plan, which is based on the sampling plan, AQL value, and various sampling plans (normal \ tightened \ relaxed, etc.). It is recommended to refer to the MIL-STD-1916 standard .

3. For example, if the production department produced 1,000 products, they found that only 990 are acceptable after a full inspection, so they are handed over to the quality control staff, and the quality control staff cannot perform a full inspection of 990. So according to the corresponding The AQL value is sampled. For example, 50 samples are sampled for inspection, and AC = 0 at this time. Once any defect is found, the production staff needs to be re-tested by 100%. Then it is processed according to the above process. Until the sampling No defect has been found so far. It should be noted how the corresponding AQL value and sample size can ensure that the chance of defective products is 0.

4. For Pre-Shipment Inspection, we must first comply with the customer ’s requirements. For example, we have adopted different AQLs for domestic and European customers, which are 0.065 and 0.65, because Europeans do not take Per-Shipment Inspection as important, but The performance requirements are particularly high. For IQC, it may be necessary to discuss with the supplier. If their long-term performance is good, they can increase the AQL appropriately. Most of them still use 0.65 and 0.1.

5. One thing that is certain is that no matter what sampling scheme you use, you should set AC = 0 in zero defects. It ’s just a matter of controversy as to how the specific Sample Size is determined. The sampling standard in the inspection process can be based on MIL-STD. -1916.


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