Molds & Tooling
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PP Part Post-demolding Deformation
Problem Phenomenon
Parts deform when ejected during demolding, or gradually deform during storage after demolding—unrecoverable, affecting assembly.
Cause Analysis
Insufficient cooling time—the part core is ejected before full crystallization and setting; PP crystallizes slowly, especially thick-walled parts; unbalanced ejection, insufficient local part rigidity, and stacking under pressure and heat after demolding also cause secondary deformation.
Solution
①Extend cooling time to ensure thick walls fully set; ②improve water circuit efficiency and balance mold temperature; ③balance the ejection system and eject at high-rigidity locations; ④pack only after parts fully cool, avoiding stacking pressure and heat; ⑤if necessary, use setting fixtures to constrain cooling.
Key Takeaway
PP 'demolding before setting' is the root of deformation: thick-walled parts need sufficient cooling time and balanced ejection; post-demolding storage and packaging are also high-incidence deformation stages—stacking hot parts equals secondary molding.
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