Pull the active core out from the molding position to a place not interfering ejection of the plastic parts, and the distance moved by the active core or slide is called core-pulling distance.
Generally, core-pulling distance equals to the depth of side hole plus a safety distance of 2—3mm. A core-pulling mechanism for pulling a slide core and a threaded-pin core in an injection mold includes a hinge shaft having two ends with polygonal cross-section, an shaft sleeve assembled with a rear of the hinge shaft, a baffle block having axial through opening allowing the hinge shaft to pass through and rotate therein, a slider having a through hole for receiving the baffle block and a semi-closed transmission hole defined in a rear wall, a transmission shaft assembled in the transmission hole and fixed to the slider, and a guide block. The baffle block and the guide block have inclined guiding bulges and inclined guiding grooves engaging with each other to guide the baffle block to slide. While the transmission shaft drives the slider to move backward, the hinge shaft following with the slider move backward and slide in the shaft sleeve, thus, the distance of the backward movement of the cores pulled by the core-pulling mechanism is not limited.