Manufacturing of Next Generation Injection Molding Dies by Laminating Thin Sheets

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This research developed a new method of making molds for injection molding of plastics. In this method, since molds are made by laminating metal sheets cut by laser, both delivery time and cost can be reduced compared with conventional die making methods. Furthermore, since channels for cooling water can be circulated arbitrarily inside the mold, higher production rate and quality of products can be achieved. Diffusion bonding was used to bond the sheets, and a mold with excellent forming efficiency and accuracy was manufactured. This research also developed a new method of temperature control for injection molding of plastics using the sheet metal laminated mold. In injection molding, the mold is normally cooled in order to shorten the forming cycle time. However, higher mold temperature is preferable during the resin filling period from the viewpoint of resin flowability. The mold temperature was thus controlled so that the core is heated during the resin filling period followed by cooling until the plastic part is ejected from the mold. The sheet metal laminated mold enables this heating and cooling cycle because channels for hot and cool water can be circulated uniformly adjacent to the mold surface. This temperature control using the sheet metal laminated mold has such advantages as high-cycle forming, improved flowability of resin, superior replicability, and high accuracy of the injection molded parts.