Effect of Cooling Variation in Core and Cavity Temperatures on Volumetric Shrinkage in the Plastic Injection Moulding Process

Abstract

Plastic injection moulding (PIM) is a widely used manufacturing process for producing high-precision plastic components. Among various process parameters thermal condition particularly core and cavity temperatures and their respective cooling rates significantly affect the volumetric shrinkage of moulded parts. Non-uniform cooling due to imbalanced temperature profiles can lead to percentage volumetric shrinkage, causing residual stresses, dimensional inaccuracies, and warpage. This study investigates the effects of core temperature, cavity temperature, and cooling time on volumetric shrinkage in the injection moulding process. A statistical approach using Design of Experiments (DOE) based on the Response Surface Methodology (RSM) was employed to analyze the relationships and interactions among these parameters. The results indicate that core temperature has the most significant parameter influence on volumetric shrinkage, followed by cavity temperature. However, cooling time alone showed minimal statistical impact. However, a notable interaction between core temperature and cooling time was observed, suggesting a synergistic effect on volumetric shrinkage behavior. Optimization of process parameters yielded optimal settings of 15 °C core temperature, 60.45 °C cavity temperature, and 12.5 s cooling time. These conditions reduced percentage volumetric shrinkage to 36.59%, significantly improving part dimensional stability. The predictive model demonstrated high accuracy, with an average differential of only 1.43% compared to experimental results. These findings highlight the critical role of thermal management and parameter interactions in minimizing volumetric shrinkage in plastic injection moulding.