Patent ID: 8882486

Claim:
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.