Control of Plastic Extruders with Multiple Temperature Zones Using a Microprocessor Based Programmable Controller System

Extrusion of molten plastic onto wire and other metal shapes requires very close control of numerous variables to ensure consistent product quality at maximum production rates. Until recent years, extrusion process control systems had to be based upon the use of timers, counters, relays, individual temperature controllers, and speed controllers. Less than satisfactory performance has been achieved by such systems due to the dependence on the human operator for the coordination of the individual controls. The advent of the programmable controller afforded the opportunity to accomplish a higher degree of coordination and extruder performance by integrating the variety of individual controls into a single system. A key element of the control integration is the performance of closed-loop temperature control by the program of the programmable controller. Results of work on the control integration are presented, followed by recommendations for further work.