Abstract: The method of die casting a metallic cast product having a hollow metallic member embedded therein by locating the hollow member in position in a casting cavity and injecting molten metal into the cavity around the hollow member including confining a pressure resisting medium within the interior of the hollow member by seals prior to injecting the molten metal into the cavity, thereby positively preventing the hollow member from being collapsed by the pressure of the molten metal injected into the cavity. The pressure resisting medium is sealingly confined within the hollow member by tightly applying a sealing plug to the respective open ends of the hollow member after the pressure resisting medium completely fills the hollow member. One of the sealing plugs may be movable in response to the increase in the internal pressure of the pressure resisting medium.

Abstract: A method and apparatus for monitoring the operation of a reciprocating liquid injection unit wherein charges of an injection liquid, such as molten metal, are injected one-by-one to a point of consumption, such as an injection molding die, by an injection plunger reciprocating in a sleeve and driven by a double acting hydraulic cylinder and fluctuations in the oil pressure on the return side of the hydraulic cylinder are monitored to detect abnormal increases in such pressure which indicate the occurrence of dragging between the injection sleeve and the plunger head.