Warpage deformation appearing in random copolymer polypropylene injection molded products

The product bends, twists or warps after demolding, with flatness out of tolerance and difficult assembly. Deformation usually gradually worsens within hours after demolding, and in severe cases the product is completely unusable; it is especially common in large flat and thin-walled products.

(1) Random copolymer polypropylene has high crystallinity; inconsistent shrinkage in all directions causes non-uniform shrinkage leading to warpage (2) Product wall thickness is uneven; thick-wall areas shrink more and thin-wall areas shrink less, producing internal stress (3) Mold temperature is uneven; cooling rate differences across cavity areas cause uneven shrinkage (4) Holding pressure distribution is uneven; pressure is high near the gate and low at the far end, with large shrinkage compensation differences (5) Cooling time is insufficient; the product is demolded before full cooling, and post-shrinkage causes deformation

(1) Optimize product design; keep wall thickness as uniform as possible, reinforcing rib thickness not exceeding 60% of wall thickness, and enlarge fillets at corners (2) Control mold temperature uniformity, with temperature difference not exceeding 5°C, reasonably set within the 40-80°C range (3) Extend cooling time to ensure the product is fully cooled and solidified before demolding; demolding temperature is more than 10°C below the heat deflection temperature (4) Optimize the holding pressure scheme, using multi-stage holding pressure to ensure uniform shrinkage compensation in all cavity areas (5) Adjust gate position and number to make melt flow uniform and reduce molecular orientation differences

Warpage deformation is a core challenge of crystalline material '2079851475616104452; its essence is internal stress caused by non-uniform shrinkage, requiring systematic control from multiple dimensions of design, process and mold.