Optimal Process Parameters Setting on Shrinkage of an Injection Molded Part using Design of Experiment Method

Abstract

Plastic injection molding is an important process to produce thin-shell plastic parts. However, the difficulty in adjusting optimum process parameters setting may cause defects of the injected molded parts such as shrinkage. In this study the author wants to investigate the process parameters which will affect the shrinkage defect on a plastic cell phone shell component. The machine process setting in use currently caused shrinkage where variations in the dimensions of the length and width below the specification limit. Therefore the experiment is needed to identify the optimal process parameters that could be set to maintain the length and width dimensions closest to the target value with smallest possible variation. The process parameters selected in this study are the mould[u1] temperature, injection pressure and screw rotation speed. The Design of Experimental (DOE) approach was used to investigate and identify the optimal moulding process parameters. The significant factors affecting the length and width of the cell phone shell were identified from ANOVA. Statistical results and analysis are used to provide better interpretation of the experiment. Confirmation run with the optimal process parameter setting found by DOE method determined that the shrinkage can be eliminate during mass production.