Monitoring and dynamic control of quality stability for injection molding process

Abstract

Stability control of production is an important aspect of injection molding. However, challenges continue to exist with respect to improving product quality stability to achieve a faster forming speed and a higher automation for injection molding because the injection process is usually disturbed by several inevitable variations. The difficulty in overcoming the fore-mentioned inevitable disturbances and achieving dynamic control of product quality is related to establishing a quantitative relationship between product quality and process variables. In this study, a quality prediction model based on polymer melt properties is established to monitor product weight variation online. A pressure integral (PI) based on the prediction model is proposed as an effective process variable to predict product weight variation. Additionally, a dynamic control method is proposed to improve product quality stability. The experimental results indicate that PI presents advantages of consistency and stability in monitoring product weight variation when compared with models proposed by extant studies. The proposed control method results in a decrease in product weight variation from 0.16% to 0.02% in the case of varying mold temperature and the number of cycles to return stability decreases from 11 to 5 in with respect to variations in the melt temperature.