Magnetic clamp device

An injection molding machine having first and second plates each of which include a magnetic body, said first plate and second plate are attached to left and right platens, respectively, and a first mold is clamped to said first plate and a second mold is clamped to said second plate, the injection molding machine comprising:

• a plurality of magnet blocks disposed on a surface of each of said first plate and said second plate, each of said plurality of magnet blocks having an invertible magnet capable of inverting polarity and a non-invertible magnet, and configured to magnetically clamp a corresponding mold in a magnetized state,
• a coil for detecting a change in magnetic flux passing through the invertible magnet, and
• a controller for determining whether or not a polarity of induced voltage detected by the coil is inverted by the change in magnetic flux and for re-magnetizing each of the first and second molds clamped by the first and second plates, respectively in a state of being matched with each other upon detecting an inversion of polarity.