Advantages of Injection Mold with Hybrid Process of Metal Powder Bed Fusion and Subtractive Process

This paper focuses on the hybrid process combin-ing metal additive manufacturing (AM) and subtrac-tive processing developed for application to injection molds. The basic concept is a combination of laser powder bed fusion of metal powder and subtractive processing. This process is characterized by alternat-ing buildup and milling processes. Even the inner sur-face of deep grooves, which conventionally required electrical discharge machining, can be machined with small-diameter tools with a short flute length. There-fore, molds with complex shapes that previously re-quired electrical discharge machining can be manu-factured in a single process. Moreover, a dimensional accuracy and surface roughness of levels equal to those achieved by machining with the machining center can be ensured. In the hybrid process, it is necessary to minimize the surplus solidified area (which is the area milled by the small-diameter tool). Therefore, the for-mation mechanism of the surplus solidified region is verified. It is shown that the power distribution of the laser beam significantly affects the size (width and depth) and density distribution of the excessively so-lidified region. In addition, the effective value of metal AM mold is introduced. The 3D cooling circuit im-proves the efficiency of the injection molding process. If the temperature balance between the cavity side and core side is achieved, the distortion of the molded product would be suppressed. If the cooling effect is promoted, the molding cycle would be shortened sub-stantially. Second, the effect of the gas vent function by a permeable structure is explained through actual examples. The effect of the gas vent function by the permeable structure is explained. It is indicated that stable molding can be achieved. In addition, the ap-pearance defects of molded products can be reduced when the air inside the cavity is exhausted sufficiently from the mold through the permeable structure.