Sampling inspection frequency is not better the denser it is; it is recommended to classify by risk:

- New suppliers/new grades: full-item inspection for the first batch, then switch to routine sampling after 3 consecutive qualified batches. - Critical applications (pressure-bearing, food, safety parts): verify the quality certificate for each batch and sample-test composition/dimensions. - General decorative applications: sample-test appearance and dimensions by batch, and periodically send samples to third parties for verification. - Stable supplier capability and good historical data: frequency can be reduced, but traceability requirements remain.

At the same time, agree on the handling process for nonconformities (return, rework, claim, supplier corrective action), so that sampling inspection truly has binding force.