Molds & Tooling
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EEA extruded film thick at edges and thin in the middle
Problem Phenomenon
EEA extruded film edges 20-30% thicker than the middle, thickness distributed in a U shape
Cause Analysis
Improper die runner design, low resistance and large flow at the edges; EEA melt elasticity, larger swell at the edges; air ring cooling has different edge effects
Solution
1) Adopt coat-hanger die design to balance resistance between the middle and edges; 2) Fine-adjust die gap, slightly larger in the middle and slightly smaller at the edges for compensation; 3) Slightly reduce air ring air volume at the edges; 4) Add restrictor bars to adjust edge flow
Key Takeaway
U-shaped thickness is caused by die runner and swell difference; coat-hanger die and gap fine adjustment are the key
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