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