Cavity pressure based grey prediction of the filling-to-packing switchover point for injection molding

Filling-to-packing switchover control during injection molding plays a crucial role in ensuring the quality of the molded parts prior to production. Although this topic has been studied for years, traditional methods of filling-to-packing switchover control, such as using screw cushioning or checking injection time without indicating the actual behaviors of melt plastics being filled into the cavity, are still those mostly used in practice. The results of switchover control, therefore, are often times inaccurate while the variation in the quality of produced parts is not negligible. This study thus presents a novel method by which quick and accurate decisions concerning the ideal switchover time can be made. It has adopted a simple grey model, GM(1,1), to predict instantaneously the volumetric-filling point when monitoring the cavity pressure profile in each molding. Recently found to be a good indicator of product quality, cavity pressure profile is applied here to obtain more precise switchover control. After the experimental verification is conducted, the results reveal that the innovative switchover method yields a more uniform product weight than any traditional methods.