Control device for an injection molding machine

摘要

To execute a stable pressure control, in a control device for an injection molding machine, a filling/pressure-keeping determining unit determines whether the injection molding machine is performing a pressure keeping operation, an elastic constant identifier acquires, when the filling/pressure-keeping determining unit determines that the pressure keeping operation is in progress, a pressure detection value and a position detection value as operation information of a motor and identifies an elastic constant K based on the acquired pressure detection value and the position detection value, and a pressure-control control-parameter setting unit calculates a proportional gain Ka of a pressure controller such that a product of the proportional gain Ka of the pressure controller and the elastic constant K is smaller than a speed control bandwidth ωsc of a speed controller, and sets the calculated proportional gain Ka to the pressure controller.

主权项

1. A control device for an injection molding machine that injects a melted resin filled in a barrel into a cavity of a mold by driving a motor to move forward a screw in the barrel, wherein the control device, which is provided in the injection molding machine, generates a current command for driving the motor based on operation information of the motor and a pressure detection value of the melted resin, the control device comprising:
a pressure controller that calculates a speed command by performing a transfer characteristic computation including a computation element that applies at least a proportional gain on a deviation between a predetermined pressure command and the pressure detection value; a speed controller that calculates the current command such that a speed of the motor follows a speed command calculated by the pressure controller; a pressure-keeping-operation determining unit that determines whether the injection molding machine is performing a pressure keeping operation; an elastic constant identifier that acquires, when the pressure-keeping-operation determining unit determines that the pressure keeping operation is in progress, the pressure detection value and the operation information of the motor and identifies an elastic constant that is a proportion of a change of the pressure detection value with respect to a displacement of a position of the motor based on the acquired pressure detection value and the operation information of the motor; and a control-parameter setting unit that calculates the proportional gain of the pressure controller such that a product of the proportional gain of the pressure controller and the elastic constant identified by the elastic constant identifier is smaller than a speed control bandwidth of the speed controller, and sets the calculated proportional gain to the pressure controller.