An adjustment mechanism for a movable platen of an injection molding machine is provided with a push bolt, configured to apply a force to push up the movable platen against a gravitational force, and a pull bolt, configured to apply a force to draw in the movable platen in the direction of gravity. The movable platen is adjusted by regulating its height above a base of the molding machine in a plurality of positions at different distances from a fixed platen.