Patent attributes
In forming a plastic mold product having an inner hole, a flash of a degree which is required to be removed in a following step is prevented from occurring. The cutter punch 12 in one of the stationary mold 1 and the movable mold 2, the gas passage 7 in at least one of the stationary mold 1 and the movable mold 2 to communicate with the cavity 54, a valve provided on a gas pipe which communicates with the gas passage 7, and a controller are provided. The cutter punch 12 is adapted to be movable between a normal position for injection of the melted resin and a projected position in which the cutter punch 12 projects into the cavity 54 so that a clearance remains between the cutter punch 12 and its counterpart at the position for forming the optical disk substrate with the inner hole, with the gas coming out of the gas passage being capable of flowing into the clearance. The controller controls the movement of the cutter punch 12 and the opening and closing of the valve in conjunction with the injection of the resin.
