Molding Process
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PET die lip buildup early warning
Fenómeno do problema
Material gradually builds up and thickens on the die lip, eventually falling off into the sheet to form black specks, scrapping the whole roll
Análise das causas
Die lip buildup is an early warning of thermal degradation of the melt at the die opening: oxidized material adheres to the lip surface and thickens until it peels off; on a transparent PET line, one peeling is a whole roll of waste
Solução
① For oxidative buildup, lower the die temperature by 10℃ and check die gap uniformity; ② clean the die lip with a copper scraper every shift; ③ when buildup is frequent, check the residence time; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Conclusão principal
Die lip buildup is a sentinel of degradation; frequent scraping plus temperature reduction plus residence time check keeps whole-roll scrapping from happening; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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