When parts manufacture combines different casts, part collection and assembly is required separately after each mold is manufactured. Combining casts and parts inside-mold would vastly improve machining performance and productivity. An example of R&D in this area is that by the Japan Steel Works, Ltd., which has been studying high-value-added production by inside-mold injection for hollow resin products used in the production of electric household appliances and automobile components. One technique is hollow injection molding by die sliding (Fig.1), in which the metal mold slides after primary molding. First, the primary product is molded by primary injection (Fig.1(b)) and the metal mold is opened, leaving the primary product in the cavity (c), then the metal mold is moved by a die slider on the injection molding machine to where primary molded products face each other (d). The metal mold is closed again (e) in secondary injection, resin is injected as a headband so that the joint of the primary molded product is wrapped and this is repeated, with injection and joining inside the same metal mold, eliminating conventional pretreatment, postprocessing, and equipment for core setting and removal. This improves total productivity and cuts overall cost. Component material is possible in forming and different forming is possible, such as multi-quality-material forming, forming of a components using different materials, forming of a component using the same material, and 2-color hollow product forming.
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