Material Drying
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PET first article full-item verification
Fenómeno del problema
After material change, bubbles and yellowing appear in batches; the first article was only visually inspected
Análisis de la causa
After PET material change, drying state, melt temperature, and filtration pressure differential may all change; visual first inspection alone cannot detect hidden deviations such as IV decline and excessive moisture content
Solución
① Perform full-item verification of moisture content, appearance, IV or melt index, and dimensions on the first article; ② additionally measure thickness and transparency on sheet first articles; ③ mass production after parameter locking; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Conclusión clave
PET first article verification must include material state indicators; full-item verification plus parameter locking is the institutional bottom line for preventing batch accidents; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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