Extrusion & Post
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CEF extrusion film thick at edges and thin in the middle
Problem Phenomenon
The edges of the CEF extruded film are 20-30% thicker than the middle, and the thickness is distributed in a U shape
Cause Analysis
The die runner design is improper, the edge resistance is low and the flow is large; the CEF melt elasticity swells more at the edges; the air ring cooling has different effects at the edges
Solution
1) The die adopts a coat-hanger design to balance the resistance between the middle and the edges; 2) Fine-tune the die gap slightly larger in the middle and slightly smaller at the edges for compensation; 3) Slightly reduce the air volume of the air ring at the edges; 4) Add a restrictor bar to adjust the edge flow
Key Takeaway
The U-shaped thickness is caused by the die runner and swell differences; the coat-hanger die and gap fine-tuning are the key
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