Extrusion & Post
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PP Sheet Die Lip Buildup
Problem Phenomenon
After a period of PP sheet extrusion, material hangs on the die lip, and periodic longitudinal streaks or lines appear on the sheet surface.
Cause Analysis
Melt stagnates and degrades at the die lip exit edge, gradually building up into deposit that periodically sheds and is pressed into the sheet surface; high raw material volatiles and mismatched exit temperature and line speed accelerate buildup.
Solution
①Regularly clean die lips with tools such as copper brushes; ②optimize exit zone temperature to avoid local overheating degradation; ③appropriately reduce line speed; ④check raw '2079851475616104451 and regrind ratio; ⑤evaluate adding processing aids to reduce stagnation.
Key Takeaway
PP die lip buildup is an accumulation process of 'stagnation degradation': cleaning treats the symptom, while temperature-speed matching treats the root; the interval pattern of periodic streaks from buildup can back-calculate the buildup shedding cycle.
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