Meaning
Statistical inspection of a representative subset from a production batch determines whether the entire quantity meets the defined quality criteria. Applying lot acceptance sampling allows a processor to verify the properties of incoming resin or finished parts without testing every individual unit. This method relies on probability to balance the risk of rejecting good material against the risk of accepting defects.
Sampling Plan
Parameters for the inspection are derived from established tables like ISO 2859. The lot acceptance sampling protocol specifies the number of parts to be drawn and the maximum number of failures allowed before the lot is quarantined. A stricter plan reduces the chance of a moulder using out of specification material.
Resin Validation
Testing melt flow rate or moisture content on a few bags represents the whole shipment. If lot acceptance sampling identifies a deviation in viscosity, the processor rejects the delivery to avoid process drift. This step protects the moulding floor from variables that the machine controller cannot correct.
Economic Limit
Destructive testing makes total inspection impossible for commercial production. Because lot acceptance sampling focuses on a fraction of the total, it keeps quality control costs within the margins of the project. The boundary of this practice is reached when the cost of a missed defect exceeds the cost of more frequent sampling.
