Mold clamping device of injection molding machine and method of adjusting mold thickness of mold clamping device

A mold clamping device of an injection molding machine comprising:

• a mold clamping shaft integrated with a mold opening/closing nut, the mold opening/closing nut is adapted to be moved by rotating a mold opening/closing screw shaft to perform opening and closing of a movable platen;
• a mold clamping ram incorporated in a support platen pressing the mold clamping shaft, the mold clamping ram hydraulically performing mold clamping of the movable platen, wherein
• the mold clamping shaft includes annular convex parts at a constant pitch on an outer circumference thereof,
• a half nut device incorporating a half nut which engages with the annular convex parts is coaxially attached to a distal end of the mold clamping ram, and
• the mold clamping shaft, the half nut device, and the mold clamping ram are disposed on one shaft,
• the mold clamping device further comprising:
• a ram position detecting member which detects a position of the mold clamping ram;
• an encoder which detects a position of the movable platen;
• a ram position control member which hydraulically controls the position of the mold clamping ram;
• a storage unit which stores a difference value between a first mold closing position of the movable platen for a first mold, and a second mold closing position of the movable platen for a second mold;
• and
• a control unit which performs is control of the mold clamping device, wherein
• the control unit calculates the difference value when mold thickness adjustment is performed, calculates a movement position of the mold clamping ram on the basis of a current position of the mold clamping ram and the difference value, moves the mold clamping ram to the movement position, and then causes the half nut to engage with the mold clamping shaft to perform the mold clamping of the movable platen.