Injection Molding
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Sink marks in EVA '2079851475616104452
Problem Phenomenon
Surface depressions of 0.2-0.5mm in thick wall areas of EVA injection molded products (sink marks)
Cause Analysis
Holding pressure insufficient or holding pressure time short; gate freezes too early with holding pressure unable to transmit; large wall thickness differences with thin walls freezing first preventing feeding of thick walls
Solution
1) Increase holding pressure to 70-90MPa; 2) Extend holding pressure to gate freezing +2s; 3) Product design reduces wall thickness differences with gradual transition; 4) Add supplementary gates in thick wall areas
Key Takeaway
Sink marks are caused by insufficient holding pressure and wall thickness differences; high pressure holding and multiple gates are the core countermeasures
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