Molds & Tooling
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EVOH Internal Shrinkage Cavities
Fenómeno do problema
Shrinkage cavities 0.5-2mm in diameter at the center of EVOH thick-walled products
Análise das causas
After cooling of the thick-walled area, the interior shrinks but the surface is already solidified and cannot be fed; holding time insufficient, gate freezes too early
Solução
1) Extend holding time until the gate fully freezes; 2) Increase gate size to delay freezing; 3) Product design to reduce wall thickness differences
Conclusão principal
Shrinkage cavities are caused by thick-wall shrinkage and insufficient holding; extending holding is key
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