Injection Molding
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EVOH '2079851475616104452 Sink Marks
Problem Phenomenon
EVOH injection molded products show 0.2-0.5mm surface depression sink marks in thick-walled areas
Cause Analysis
Insufficient holding pressure or short holding time; gate freezes too early so holding pressure cannot be transmitted; large wall thickness differences, after thin walls freeze the thick walls cannot be fed
Solution
1) Increase holding pressure to 70-90MPa; 2) Extend holding to gate freeze +2s; 3) Product design to reduce wall thickness differences with gradual transitions; 4) Add supplementary gates in thick-walled areas
Key Takeaway
Sink marks are caused by insufficient holding and wall thickness differences; high holding pressure and multiple gates are the core countermeasures
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