Optimization of injection molding process to minimize weld-line defects and improve dimensional accuracy of the plastic parts using Taguchi-based grey relational analysis

In the precision molding of transparent Polycarbonate (PC) electronic housings, manufacturers face an inherent conflict: the high processing temperatures required to minimize visible weld-line defects often trigger volumetric shrinkage that compromises the strict dimensional tolerances necessary for complex assembly. This study addresses this gap by presenting a novel, data-efficient optimization framework that simultaneously resolves these traditionally conflicting objectives under real industrial manufacturing conditions. Utilizing a Taguchi L16 orthogonal array integrated with multi-objective Grey Relational Analysis (GRA) and average Signal-to-Noise Ratio (SNR) consistency checks, the process reached an optimal configuration (70 °C mold temperature, 305 °C melt temperature, 75 mm/s fill velocity, 35 MPa holding pressure, and 20 s cooling time). Validation experiments achieved a significant reduction in weld-line width (WLW) of 57.00%, while dimensional deviations were improved by 85.92% and 50.90% compared to initial averages. Analysis of Variance (ANOVA) identified holding pressure (26.49%) and fill velocity (25.74%) as the dominant drivers for dimensional precision and overall aesthetic quality, respectively. This approach provides a robust, cost-effective guideline for precision manufacturing, ensuring that aesthetic enhancements do not hinder the mechanical fit in high-complexity electronic assemblies.