A Novel Process Control Methodology Based on the PVT Behavior of Polymer for Injection Molding

Based on the PVT (pressurevolumetemperature) behavior of polymer, a novel process control methodology for injection molding is presented in this study. With the present control method, the process pressure is controlled by cavity temperature instead of time, which is used in a conventional injection-molding process; thus the relationship between P (pressure) and T (temperature) can be controlled, which means that the V (volume) or part weight can be controlled because of the invariable PVT relationship of polymer. The objective of this study is to validate the feasibility of this process control methodology and examine its consistency. Experiments were conducted on an injection-molding machine with an opened-loop microprocessor controller. The weight of the molded parts serves as the main measure to probe the process capabilities. The variation of the mold temperature was monitored. The experimental results reveal that the present PVT control method yields much better part quality and uniform part weight than the conventional Ptime (pressuretime) control method. It is also proved that the novel process control methodology can be used to accommodate the product weight change due to variation of the melt or mold temperature. (c) 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E474E485, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21294