This paper describes the results of fundamental experiments conducted by injection mold with permeability fabricated by Metal Laser Sintering Combined with High Speed Milling. Metal Laser Sintering Combined with High Speed Milling is attracting attention as a new mold fabrication approach. This machining method combines the metallic powder layer fabrication method with high-speed cutting. Since this process does not have the problem of tool L/D in usual cutting, it provides outstanding shape machining performance of deep ribs etc. Moreover, with this processing method, sintered density can be controlled by changing the exposure conditions of the laser beam, and gas permeable structures can also be manufactured. This fabrication method does not require the mold to be divided. From these features, this method is expected to offer such advantages as quick delivery of molds and low manufacturing costs. However, little is known about the application of laser sintered metallic molds which have gas permeability structure to plastic injection molding, and the practical use of these molds is not easy. The aim of this research was therefore to investigate the gas permeable structures realized by laser sintered metallic mold in plastic injection molding The results confirmed that permeable injection molds are effective for influencing residue air in products.

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This paper discusses design methods for the internal structure of molds used in production utilizing metal laser sintering combined with high speedmilling which selectively sinters metal powder to form a three dimensional mold. This milling technique is characterized by the fact that the selective laser sintering process and milling process are carried out in alternating sequence, achieving the level of processing accuracy demanded of mold production. In addition, in the selective laser sintering process, because the mechanical strength of the sintered body (Young’s Modulus) is variable, suitable interior structures that consider dynamic conditions are expected. However, in the current state of design, this structure is determined experimentally, and there is a high possibility of incurring unnecessary production time and high costs. In this paper, we investigate a method that incorporates an optimization method using stress that occurs within the structure interior, obtains the interior topological structure as a Young’s Modulus distribution, and designs a suitable interior structure using this distribution. As a result of investigation using numerical analysis, we obtained a structure that reduces the volume of the sintered body, having high mechanical strength in comparison with a conventional structure while improving structural rigidity.

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