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