Control device and control method for injection molding machine

An injection molding machine including a cylinder into which a resin is supplied, and a screw configured to move forward and rearward and rotate inside the cylinder, the injection molding machine being configured to perform a metering of the resin while the resin is being melted inside the cylinder, by causing the screw to be moved rearward to a predetermined metering position while being forwardly rotated, the injection molding comprising:

• a control device including:
• a computation unit configured by a processor;
• and
• a storage unit, the storage unit storing instructions to cause the processor to control:
• a pressure acquisition unit configured to acquire a resin pressure inside the cylinder;
• a reverse rotation control unit configured to cause the screw to be rotated in reverse based on a predetermined reverse rotation condition so as to reduce the resin pressure, after having moved the screw rearward to the metering position;
• a compensation amount calculation unit configured to calculate a compensation amount to be made with respect to the reverse rotation condition, based on the resin pressure inside the cylinder acquired by the pressure acquisition unit when the reverse rotation of the screw is stopped, and a predetermined compensation function;
• a compensation processing unit configured to compensate the reverse rotation condition based on the compensation amount calculated by the compensation amount calculation unit;
• and
• a compensation amount storage unit configured to store the compensation amount calculated by the compensation amount calculation unit;
• a first drive device configured to rotate the screw;
• and
• a second drive device configured to move the screw,
• wherein the compensation processing unit determines, as a reverse rotation condition at a next time of injection molding, a reverse rotation condition obtained by compensating the reverse rotation condition at a current time of injection molding, based on the compensation amount stored in the compensation amount storage unit when the current time of injection molding is performed,
• wherein the control device is further configured to send control signals to the first drive device instructing the first drive device to rotate the screw, and
• wherein the control device is further configured to send control signals to the second drive device instructing the second drive device to move the screw.

A method of controlling an injection molding machine including a cylinder into which a resin is supplied, and a screw configured to move forward and rearward and rotate inside the cylinder, the injection molding machine being configured to perform a metering of the resin while the resin is being melted inside the cylinder, by causing the screw to be moved rearward to a predetermined metering position while being forwardly rotated, the method comprising:

• a step of causing the screw to be rotated in reverse based on a predetermined reverse rotation condition so as to reduce a resin pressure, after having moved the screw rearward to the metering position;
• a step of acquiring the resin pressure inside the cylinder when the reverse rotation of the screw is stopped;
• a step of calculating a compensation amount to be made with respect to the reverse rotation condition, based on the resin pressure inside the cylinder acquired when the reverse rotation of the screw is stopped, and a predetermined compensation function;
• and
• a step of compensating the reverse rotation condition based on the calculated compensation amount;
• a step of determining, as the reverse rotation condition at a next time of injection molding, the reverse rotation condition obtained by compensating the reverse rotation condition at a current time of injection molding;
• and
• based on the resin pressure and the compensation amount, a step of sending control signals instructing the injection molding machine to rotate the screw and to move the screw.