Injection Molding
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Warpage deformation of homopolymer polypropylene injection products
Fenómeno do problema
The product shows bending, twisting, or warpage deformation after demolding, flatness out of tolerance, assembly difficult.
Deformation usually gradually intensifies within hours after demolding; in severe cases the product is completely unusable, especially common in large flat and thin-wall products.
Análise das causas
(1) High crystallinity of homopolymer polypropylene; inconsistent shrinkage in each direction, non-uniform shrinkage causes warpage
(2) Uneven product wall thickness; thick-wall areas shrink more, thin-wall areas shrink less, producing internal stress
(3) Uneven mold temperature; cooling rate differences across cavity parts cause uneven shrinkage
(4) Uneven holding pressure distribution; high pressure near the gate, low pressure at the far end, large shrinkage compensation differences
(5) Insufficient cooling time; product demolded before fully cooled, post-shrinkage causes deformation
Solução
(1) Optimize product design; wall thickness as uniform as possible, rib thickness not exceeding 60% of wall thickness, enlarge fillets at corners
(2) Control mold temperature uniformity, temperature difference not exceeding 5°C, reasonably set within the 40-90°C range
(3) Extend cooling time, ensure the product is fully cooled and solidified before demolding, demolding temperature more than 10°C below heat deflection temperature
(4) Optimize holding pressure scheme, adopt multi-stage holding pressure, ensure uniform shrinkage compensation in all cavity parts
(5) Adjust gate position and number, make melt flow uniform, reduce molecular orientation differences
Conclusão principal
Warpage deformation is the core challenge of '2079851475616104452 crystalline materials; its essence is internal stress caused by non-uniform shrinkage, requiring systematic control from design, process, and mold in multiple dimensions.
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