Influence of Process Parameters on Shrinkage/Warpage and Tensile Strength in ABS/PC Injection Overmolded Products

ABSTRACT The limited esthetic appeal of conventional plastic products has led to increased consumer demand for visually enhanced alternatives. This shift has driven the growing use of over‐molding and multi‐component injection molding technologies, particularly in automotive applications such as rear directional light covers. However, the mechanical and dimensional properties of such components are significantly influenced by processing parameters—including melt temperature, mold temperature, injection speed, packing pressure, and cooling time—as well as the compatibility and interaction between different polymers. This study examines the influence of processing conditions on the shrinkage, warpage, and tensile strength of overlapped overmolded parts composed of Acrylonitrile Butadiene Styrene (ABS) and Polycarbonate (PC). Both neat and glass fiber‐reinforced PC/ABS materials were investigated. The Taguchi method was employed to systematically evaluate the effects of process parameters on dimensional stability and mechanical performance. The findings reveal that cooling time plays a critical role in controlling shrinkage, warpage, and tensile strength. When the cooling time was increased from 4 to 12 s, the shrinkage and warpage were reduced from 7.68 to 4.35 mm, an improvement of 40% for the neat ABS/PC sample. Glass fiber‐reinforced ABS/PC composites demonstrated significantly improved performance compared to neat counterparts, exhibiting reduced deformation and higher mechanical strength. The benefit of adding glass fiber to the neat polymer for reducing shrinkage and warpage was evident, as it decreased from 7.78 to 5.17 mm at a 4‐s cooling rate, an improvement of 33.5%. Furthermore, a melt wash‐out phenomenon was observed at the ABS gate area during PC over‐molding, underscoring the importance of optimizing flow behavior in multi‐material injection molding.