Injection Molding
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Ejection Whitening on PU Injection Molded Products
Problem Phenomenon
White marks (ejection whitening) appear at ejector pin positions on PU injection molded products, affecting appearance
Cause Analysis
Ejector pin force too large causing local compression deformation whitening; cooling time insufficient, product ejected before fully cured; ejector pin area too small, stress concentration
Solution
1) Extend cooling time to fully cure the product before ejection; 2) Increase ejector pin area, use an ejector plate to replace small pins; 3) Reduce ejection speed to decrease impact force; 4) Increase draft angle to reduce ejection force
Key Takeaway
Ejection whitening is caused by excessive ejection force and insufficient cooling; increasing ejector pin area and extending cooling time are key
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