Effective Cooling and Accuracy Improvement in Injection Molding Using a Metal Mold with Cooling Channels Composed by Laser Sintering (3rd Report): Cooling by the Steel Powder Mold with Cooling Channels

摘要

冷却水路を内部に持つ射出成形金型を, スティール粉体レーザ焼結造形法を用いて作成した. 箱形の成形品を対象とし, コアコーナ部に水路を設けることで、コア表面の温度分布が均一化し、成形品のソリが, 通常の金型による成形品と比べて著しく低減した. コア側の水温をキャビティ側の水温よりも適切に低くすることによって, 成形品のソリを最小にすることができた. An injection mold with inside cooling water channels which are difficult to be made by conventional machining method has been fabricated by using selective laser sintering of steel powders. A box shape work piece has been applied as a test structure. By the cooling inside the corner of the core, the temperature difference in the core surface is reduced and then the dimension accuracy of the work piece is improved compared with the work piece injected in the conventional machined mold with outside cooling channels. The core surface temperature is directly controlled by the cooling water temperature and kept constant at the end of each shot. When the water temperature of the inside channel in the core is assigned properly lower than that of outside channel in the cavity, the warp of the periphery of the box became minimum. Although the heat conductivity of the sintered material is lower than that of mold steel, cooling effect and accuracy improvement are promoted by the combination of cooling channels near the mold surface and adequate cooling temperatures.