Electric injection molding machine for controlling injection speed and injection pressure of electric injection molding machine

An injection velocity and injection pressure controlling method for an electric injecting molder wherein, when an injection screw disposed in an injection cylinder is driven to move in forward and backward directions by an electric motor to inject resin material in said injection cylinder into a metal mold to fill said metal mold, said electric motor is first velocity-controlled to fill the resin material into said metal mold and, after the resin material is filled, said electric motor is pressure-controlled to replenish the resin material for shrinkage of the resin, characterized in that wherein

• at least before changeover from the velocity control to the pressure control upon the velocity control, a velocity target value for said injection screw is corrected in response to a detection value of force applied to the resin material so that the velocity target value for said injection screw may decrease as the force detection value increases to perform velocity feedback control of said electric motor so that a detection value of the velocity of said injection screw may be equal to the velocity target value, and
• changeover from the velocity control to the pressure control is performed after the position of said injection screw in the forward and backward direction reaches a predetermined position set in advance, but
• upon the pressure control, the velocity target value is determined in response to a difference between the force detection value and a force target value to be applied to the resin material and said electric motor is velocity feedback controlled so that the velocity detection value may be equal to the determined velocity target value to perform control so that the force detection value and the force target value may coincide with each other.

An electric injecting molder, comprising:

• an injection screw, which is disposed in an injection cylinder, driven to move in forward and backward directions by an electric motor to inject resin material in said injection cylinder into a metal mold to fill said metal mold;
• a position detector configured to detect or estimate the position of said injection screw in the forward and backward direction, said position detector having an encoder configured to detect the position of the motor;
• a velocity detector configured to detect or estimate the velocity of said injection screw in the forward and backward direction, said velocity detector having an encoder configured to detect the position of the motor and a calculator time configured to differentiate the position of the motor detected by the encoder;
• a force detector configured to detect or estimate the force applied to the resin material in said metal mold, said force detector having a mold internal pressure sensor configured to directly detect the pressure in the molding space in said metal mold;
• and
• a controller, which has a velocity-control section configured to velocity control said electric motor when the resin material is filled into said metal mold, a pressure control section configured to pressure-control said electric motor when the resin material is replenished for shrinkage of the resin after the resin material is filled, and a changeover section configured to perform a changeover from the velocity control to the pressure control after a position detection value from said position detector reaches a predetermined position set in advance, wherein
• said velocity control section corrects, at least before the changeover from the velocity control to the pressure control upon the velocity control, a velocity target value for said injection screw in response to a force detection value from said force detector so that the velocity target value for said injection screw may decrease as the force detection value increases to perform velocity feedback control of said electric motor so that the velocity detection value from said velocity detector may be equal to the velocity target value, and
• said pressure-control section determines, upon the pressure control, the velocity target value in response to a difference between the force detection value and a force target value to be applied to the resin material, and velocity feedback controls said electric motor so that the velocity detection value may be equal to the determined velocity target value to perform control so that the force detection value and the force target value may coincide with each other.