Fusible core injection molding

Fusible core injection molding or Lost Core injection molding is a specialized plastic injection molding process. It is used in the manufacture of molded components with cavities or undercuts, which would not be possible with tools having demoldable cores.

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Description

The process consists of three essential steps: First, a core consisting of a low melting point metal is poured in the shape of the cavity specified for the molded component. This is inserted into the injection mold in the second step and injected with plastic. Molded component and core are both demolded and, in the third step, immersed in a heated bath to melt out the core. The bath temperature is selected to be somewhat higher than that of the core alloy’s melting point, but not so that the injected part would be damaged. Induction heating of the core metal in the heated bath reduces the melt out time to a few minutes. Liquid core metal collects on the bottom of the heated bath and is usable for a new core.

Application

The application of the fusible core process is not limited just to the injection of thermoplastics, but with corresponding core alloys also to thermosetting plastic molding materials (duroplast). The fusible core process finds application, for example, for injection molded passenger car engine intake manifolds. By modifying the equipment, small molded parts like valves or pump housings can be manufactured, as the manufacture of the fusible cores and the injected parts can be carried out on an injection molding machine.