Controlling Process Parameters during Plasticizing Stage in Plastic Injection Molding

This study aims at controlling the two process parameters, screw rotational speed and hydraulic back pressure during plasticizing stage of injection molding (IM) process, which can lead to better product quality control and minimize part rejects. The controller used in this research is dynamic matrix control (DMC), which is capable of handling the IM processes. DMC is a commonly used predictive controller and can control processes that have non-linear, multivariable, and time delay characteristics. Several experiments were conducted on the injection molding machine (IMM) in order to formulate models of the screw rotational speed and hydraulic back pressure processes. The models were used to perform control simulations using the DMC scheme. From these simulations, it was shown that DMC can be used to control the IM processes during plasticization. Practical implementation of the controller was conducted and the control performance of the developed DMC algorithm. To the best of my knowledge, this research represents the first time that MIMO MPC is used for controlling hydraulic back pressure and screw rotational speed in injection molding. The results of this study demonstrate that future studies on polymer viscosity control could be conducted using models that relate it to screw rotational speed and hydraulic back pressure.