A device for molding a plastic component having at least one undercut is disclosed herein. The device including; a fixed block and a mobile block, the fixed block and the mobile block joining along a joining plane and defining first and second cavities defining a molding cavity to receive the plastic, the molding cavity having a first volume and a main direction of demolding; means of separating the mobile block from the fixed block; at least one mobile insert placed in the fixed block; thrusting means urging the mobile insert toward the mobile block; means for moving the at least one mobile element in a secondary direction not parallel to the main direction of demolding.