Temperature Control in Injection Molding Including Zone Interaction and Backpressure

Wan Gui Li

Date:  Wednesday, Sept. 10, 2003
Time:  9:30 a.m. to 10:20 a.m.
Place: Room H-128
       Head Hall
       University of New Brunswick
       Fredericton

This research develops a mathematical model for the dynamics of a plastic Injection Molding Machine (IMM) that may be used for the design of a temperature control system. The model explicitly includes the effects of zone interaction and backpressure. A series of experiments were conducted on a 150-tonne IMM to identify the parameters of the proposed model using measurements of zone temperatures, heater input, backpressure, and screw speed. The identified model was validated using a series of blind tests that compared the model output with the measured temperatures of the IMM. This research develops a mathematical model for the dynamics of a plastic

For each zone of the IMM, a model predictive controller was designed that exploits the knowledge of the identified model. In particular, there is feedback of zone temperature and a feed forward component that includes the zone interactions and backpressure. The entire control system design was simulated mathematically and a sensitivity analysis was performed for verification. The design was then implemented and tested on the IMM. A series of experiments were conducted demonstrating superior performance when compared to PID control scheme.