Research on Bi-Objective Optimization of Injection Molding Process and Mechanical Anisotropy of Glass Fiber-Reinforced Polypropylene Fan Face Shell Based on RSM and NSGA-II

Large glass fiber-reinforced polypropylene (GF-PP) shells are widely used in HVAC and automotive industries, but their injection molding suffers from severe warpage deformation, residual stress concentration, and inaccurate mechanical performance prediction due to neglected molding history. This study proposes an integrated optimization framework for a 30% GF-PP fan face shell. The optimal two-gate molding configuration was determined via Moldflow simulation. A Central Composite Design (CCD) combined with NSGA-II was used to optimize process parameters for minimizing warpage and residual stress. A Moldflow-Ansys co-simulation process was established to characterize fiber orientation-induced mechanical anisotropy, and full-scale mold trials were conducted for validation. The optimized process reduced maximum warpage by 58.03% (from 5.299 mm to 2.224 mm) and residual stress by 13.67% (from 54.93 MPa to 47.42 MPa). The average tensile modulus along the flow direction was 1.85 times that perpendicular to the flow direction. Mold trial results showed a warpage prediction error of only 7.583%. The proposed framework effectively addresses the critical quality issues in large GF-PP injection molding, providing a systematic engineering solution for molding quality control and accurate performance characterization.