Process optimization of plastic injection molding for minimal residual stress

Abstract

This thesis summarizes the progress made in developing a procedure to optimize a plastic injection molding process by minimizing the dimensional instability of a critical feature. It documents the steps taken by a development team at the Visteon facility in Belfast, Northern Ireland to apply Design of Experiments (DOE) in process research for the production of a plastic throttle body. The team demonstrated the feasibility of using designed experiments to understand the effects of five main process parameters; melt temperature, injection speed, hold pressure, mold temperature, and cooling time, on the deformation caused by thermal cycle exposure. The experiment results and analysis were successful in establishing a prediction model for the critical dimensions of the component before and after thermal exposure. The prediction model and additional testing indicated that adjustments to the process would reduce the dimensional shift of the bore radius by over fifty percent. The thesis stresses the use of a team approach and the application of analytical methods to better understand the process. The report also includes a brief discussion of the use of Computer Aided Engineering (CAE) techniques to improve the product development process.