Post-Consumer Recyclate Quality Assurance Protocol Selection
Verify post-consumer resin lot conformity by combining core lance sampling, melt flow shear sweeps, and DSC purity screens before unloading silos.
ISO 2859
Meaning
International standard that establishes sampling schemes and procedures for inspection by attributes of manufactured lots. In polymer moulding, adherence to ISO 2859 ensures that batch quality is assessed using mathematically sound sample sizes. This standard provides clear rules for switching between normal, tightened, and reduced inspection based on history.
Companies utilize these tables to maintain consistent quality agreements with material suppliers and OEM customers.
Inprocess Verification
Inspection by attributes involves classifying each sampled part simply as conforming or non-conforming. This binary check is much faster than measuring multiple dimensional tolerances on every sample. The ISO 2859 tables dictate the exact number of parts to inspect based on the batch size and the chosen quality level.
For example, a larger production lot requires a larger sample, but the percentage of parts inspected actually decreases. This approach optimizes the labor hours spent on the quality control floor.
Inspection Intensity
The standard offers three general inspection levels and four special levels for varying risk scenarios. Level two is the default for most industrial moulding runs, balancing inspection cost and protection. Level three is used when a supplier has had recent quality failures, requiring a larger sample size to accept the lot.
These adjustments occur dynamically based on the performance of the moulder.
Inspection Frequency
To reward high-quality suppliers, the standard defines specific rules for transitioning to reduced inspection. If ten consecutive batches are accepted under normal inspection, the moulder is permitted to reduce the sample size, lowering testing costs. Conversely, if two out of five consecutive batches are rejected, the protocol automatically switches to tightened inspection, requiring larger sample sizes and stricter acceptance criteria.
This transition remains in force until five consecutive batches are accepted, proving that the process has been brought back under control. Implementing these switching rules provides a strong commercial incentive for the moulder to maintain strict process control throughout the production contract.