Processing Machinery
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PBT Black Specks and Burning
Fenómeno del problema
Black specks and burnt streaks appear on the product; cleaning the barrel improves it for a short time but it recurs
Análisis de la causa
PBT degrades when the barrel temperature exceeds 275°C or the residence exceeds 30 minutes; a low nozzle temperature causes the sprue to solidify and block the nozzle, leading to local overheating; recycling the sprue of flame-retardant material and glass fiber material also introduces degradation products
Solución
①Control barrel temperature and residence time; ②Appropriately increase the nozzle temperature to prevent solidification and nozzle blockage; ③When shutting down, promptly clean the barrel with PE or PP; after adjustment, take samples continuously to verify the effect, and resume mass production only after confirming stability
Conclusión clave
PBT black specks and burning are investigated along three lines: temperature, residence, and nozzle; PE/PP cleaning at shutdown is an iron rule to prevent carbonization; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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