Abstract
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.
