Molding Process
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DSTDP extruded film thick edges and thin middle
Problem Phenomenon
DSTDP extruded film edges 20-30% thicker than the middle, thickness showing a U-shaped distribution
Cause Analysis
Improper die flow channel design, edge resistance low and flow large; DSTDP melt elasticity swells more at the edges; air ring cooling has different edge effects
Solution
1) Adopt coat-hanger die design to balance middle and edge resistance; 2) fine-adjust die gap, slightly larger in the middle and slightly smaller at the edges to compensate; 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 differences; coat-hanger die and gap fine adjustment are key
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