| abstract |
An improved temperature control system using a state controller with two degrees of freedom to regulate the temperature of the barrel of an injection molding machine is disclosed. The control system divides the temperature of the barrel into longitudinally-extending zones and radially extending layers within each zone. Heat transfer calculations which include the effects of heat transfer between all the layers within the zones are performed for a set time in the future to accurately determine the heat needed from the heater band to reach the operator set point temperature. The duty cycle for the heater bands is thus accurately set to give a more responsive and accurate control than heretofore possible. The controller additionally includes factors for accounting for heat disturbances present in the injection molding process. In addition each system is calibrated for each machine to insure accurate formulation of machine specific parameters such as heat transfer co-efficients used in the control. |