Molds & Tooling
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PVA internal shrinkage voids
Problem Phenomenon
PVA thick-wall product center shrinkage voids diameter 0.5-2mm
Cause Analysis
After cooling of the thick-wall area, the interior shrinks but the surface has solidified and cannot be fed; holding time insufficient, gate freezes too early
Solution
1) Extend holding time until the gate is completely frozen; 2) Increase gate size to delay freezing; 3) Product design to reduce wall thickness differences
Key Takeaway
Shrinkage voids are caused by thick-wall shrinkage and insufficient holding; extending holding is the key
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