Hardware plastic injection molding When the injection molding part is demoulded from the molding mold, the demoulding force and the opening force should be overcome. Mold opening means that the shape of the plastic part comes out of the cavity. During the refrigeration process, the plastic part in the mold shrinks, and the hole wall produces a wrapping force on the core. The friction between plastic parts and cores occurs during the opening process, and the vacuum adsorption of the hole bottom seal occurs during the opening process. Many reasons indicate that the demoulding force is far greater than the opening force. Excessive demoulding force will deform, whiten, wrinkle and scratch the plastic parts. The demoulding slope is a main factor to determine the demoulding force. Since the injection molded parts are usually attached to the punch after refrigeration and shrinkage, in order to make the product thickness symmetrical and avoid the product attaching to the hot die after mold opening, the mold angle should be equal to the die and punch. However, under special circumstances, if the plastic injection molding processing and manufacturing enterprises require the commodities to be attached to the die after the mold is opened, they can appropriately reduce the mold angle of connecting the die, or deliberately add an appropriate amount of undercut to the die.

The strength of plastic parts does not increase completely with the increase of their thickness. On the contrary, the internal stress caused by shrinkage due to the increase of thickness decreases its strength. The strength of plastic parts is mainly stiffness, and most of them are thin-walled composite structures. Stiffeners are set at corresponding positions to improve the section inertia moment.