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