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 metal powders. By the cooling inside the corner of the core, the temperature difference in the mold is reduced and then the dimension accuracy of the work piece is improved compared with the work piece injected in the mold with outside cooling channels. When the water temperature of the inside channel in the core is assigned lower than that of outside channel in the cavity, the temperature distribution in the mold becomes more uniform and the dimension accuracy of the work piece has been further improved. After the experiment, the structure of the sintered mold and its thermal conductivity has been measured to consider on the relation with temperature distribution in the mold. In order to achieve the uniform temperature distribution in the mold, adequate channels location will be necessary in relation with the thermal conductivity of the mold.
