Extrusion & Post
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POE extrusion film thick edges and thin middle
Problem Phenomenon
POE extruded film edges 20-30% thicker than the middle, thickness in U-shaped distribution
Cause Analysis
Improper die flow channel design, edge resistance low and flow large; POE melt elasticity causes greater swell at the edges; air ring cooling has different edge effects
Solution
1) Adopt coat-hanger design for the die to balance middle and edge resistance; 2) Die gap fine adjustment, middle slightly larger and edges slightly smaller for compensation; 3) Slightly reduce air ring edge air volume; 4) Add restrictor bar to adjust edge flow
Key Takeaway
U-shaped thickness is caused by die flow channel and swell difference; coat-hanger die and gap fine adjustment are key
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