Molds & Tooling
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EMA internal shrinkage voids
Problem Phenomenon
Shrinkage voids of 0.5-2mm diameter at the center of thick-walled EMA products
Cause Analysis
Thick wall area shrinks internally after cooling but surface already solidified preventing feeding; holding pressure time insufficient with gate freezing too early
Solution
1) Extend holding pressure time until gate completely freezes; 2) Increase gate size to delay freezing; 3) Product design reduces wall thickness differences
Key Takeaway
Shrinkage voids are caused by thick wall shrinkage and insufficient holding pressure; extending holding pressure is key
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