OPTIMIZATION OF PROCESS PARAMETERS FOR REDUCING SHORT SHOT DEFECTS IN INJECTION MOLDING: A CASE STUDY OF AN ELECTRICAL APPLIANCE FACTORY

Abstract

This research aims to determine the optimal process parameters for plastic injection molding in order to reduce the occurrence of short shot in AC power cord plug production. Short shot is one of the most critical defects affecting product quality and manufacturing efficiency in the studied factory. Production data collected between January and December 2024 showed that 19,957 defective parts were identified as short shot out of a total production of 1,674,504 parts, representing 1.2% of total production. To investigate the root causes of the problem, data collection and brainstorming sessions were conducted with the production team, followed by root cause analysis using a cause-and-effect diagram. Three key process parameters influencing short shot were identified: melt temperature, injection pressure, and injection speed. The injection molding process was then simulated using SolidWorks Plastics to analyze melt flow behavior and determine appropriate parameter ranges. A full factorial experimental design (3³ factorial design) was applied to evaluate the effects of these parameters on the filling behavior of molten plastic. Simulation results indicated that injection temperature and injection pressure significantly affected the filling behavior. The optimal process conditions for minimizing short shot were a melt temperature of 200 °C, an injection pressure of 90 MPa, and an injection speed of 70 mm/s, with a gate size of 10 sqr.mm. Validation experiments under actual production conditions confirmed the effectiveness of the optimized parameters. During the validation period, 411,643 parts were produced, of which 1,309 parts were identified as short shot, corresponding to a defect rate of 0.32%. These results demonstrate that appropriate optimization of process parameters can effectively reduce short shot and improve production quality in plastic injection molding processes.