Molding Process
5 views
EVA extruded film thick at edges and thin in middle
Problem Phenomenon
EVA extruded film edges 20-30% thicker than middle with U-shaped thickness distribution
Cause Analysis
Improper die flow channel design with low edge resistance and large flow; EVA melt elasticity with greater swell at edges; air ring cooling with different edge effect
Solution
1) Adopt coat-hanger design for die to balance resistance between middle and edges; 2) Fine-tune die gap slightly larger in middle and slightly smaller at edges 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 differences; coat-hanger die and gap fine-tuning are key
Was this helpful?
0 people found this helpful
Thank you for your feedback!