Principle: prevent unqualified products from flowing to users, avoid user losses and protect corporate reputation. The contents of finished product inspection include: product performance, accuracy, safety and appearance. Packaging is not allowed until the finished product is qualified.

For products that leave the factory immediately after the finished product is made, the finished product inspection is also the factory inspection; For products that do not leave the factory immediately after the finished product is made, but need to be put into storage, a "factory inspection" is needed before leaving the factory. For example, the completion inspection of some military products is often divided into two stages, namely, the comprehensive inspection after the final assembly and the re-inspection after the shooting range test.

The preventive function of inspection is mainly manifested in the following two aspects:

1, which plays a preventive role through the determination of process capability and the use of control chart.

As we all know, whether it is the determination of process capability or the use of control chart, it is necessary to obtain a batch or a group of data through product inspection and carry out statistical processing. The purpose of this inspection is not to judge whether a batch or a group of products is qualified, but to calculate the ability of the process and reflect the state of the production process.

If it is found that the process capacity is insufficient, or the control chart shows that there is an abnormal state in the production process, technical organization measures should be taken in time to improve the process capacity or eliminate abnormal factors in the production process to prevent the occurrence of unqualified products. Facts have proved that the preventive effect of this inspection is very effective.

2, through the first inspection and inspection in process production, play a preventive role.

When a batch of products is in the initial processing state, the first piece inspection should generally be carried out (there is not necessarily only one first piece inspection). After the first piece is inspected and approved, it can be put into production in batches. In addition, when the equipment is repaired or readjusted, the first article inspection should also be carried out to prevent a large number of unqualified products.

After formal mass production, in order to find out whether the production process has changed and whether there is the possibility of unqualified products in time, it is necessary to conduct spot checks (that is, inspection) on the spot regularly or irregularly. Once problems are found, measures should be taken to correct them in time to prevent the occurrence of nonconforming products.