Investment casting process which includes: attaching a gate to a pattern made of a plastic to form a pattern assembly; forming a mold by applying a plaster slurry on an outer surface of the pattern assembly; dissolving and removing the pattern assembly in the mold by applying an organic solvent; burning the mold from which the pattern has been removed; casting by pouring a molten metal into the burned mold; and breaking the mold to take out a cast product.
In order to solve the above problem, the investment casting process of the present invention comprises the steps of an assembly step of attaching a gate, runner, sprue, etc., to a pattern made of a hard plastic; a molding step of forming a mold comprising a plaster mix for a mold and/or a ceramics slurry on the surface of the resulting pattern assembly; a pattern dissolving step of dissolving and removing the pattern assembly in the mold by using an organic solvent; a burning step of burning the mold from which the pattern assembly has been removed; a casting step of pouring a molten metal in the burned mold; and a mold breaking step of breaking the mold to take out a cast product.
The investment casting process of the present invention uses a pattern made of a hard plastic as a prototype. Thus, as compared with the conventional wax pattern, in the present invention, the strength of the pattern is high and the possibility of deformation or breakage of the pattern is small so that even at a portion such as a thin rod-like portion, etc., the pattern is scarcely deformed during a molding step. Therefore, the ability to duplicate a product having such a complicated portion is excellent.
The hard plastic to be used in the present invention includes a hard vinyl chloride (a polyvinyl chloride or a vinyl chloride-vinyl acetate copolymer), a polyethylene, a polypropylene, a styrol resin, etc., which are all thermoplastic resins.
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