Molding Process
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EAA extruded film thick at the edges and thin in the middle
Problem Phenomenon
The edges of EAA extruded film are 20-30% thicker than the middle, the thickness shows a U-shaped distribution
Cause Analysis
Improper die flow channel design, low edge resistance and large flow; EAA melt elasticity swells more at the edges; air ring cooling has different effects at the edges
Solution
1) Use a coat-hanger design for the die to balance the resistance of the middle and the edges; 2) Fine-tune the die gap, slightly larger in the middle and slightly smaller at the edges to compensate; 3) Slightly reduce the air volume at the edges of the air ring; 4) Add restrictor bars to adjust the edge flow
Key Takeaway
The U-shaped thickness is caused by the die flow channel and swell differences; coat-hanger die and gap fine-tuning are the key
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