Vol.11 No.2 2018

報告:Additive manufacturing of ceramic components (大司)−89−Synthesiology Vol.11 No.2(2018)and flexural strength of PLM-produced SiSiC with those of the conventionally manufactured high-rigidity SiSiC.[26] It should be noted that specific stiffness, which is the most important property for stage application, equals to that of the conventional ones. R&D should proceed for improving exural strength to 320 MPa or higher.One of the advantages of AM is its capability of producing complex-shaped parts directly from computer aided design les or data. Using computer simulation based on structural topology optimization techniques, it is now possible to optimize rib structures of stage models. Figure 9 shows an optimal rib structure obtained thereby in comparison with a conventional one, and a SiSiC exposure stage model (green body) produced by PLM based on that structure.[22] The weight is reduced to half or less while maintaining the same vertical stiffness (the simulation neglects horizontal stiness). The thinnest part of the model is approximately 3 mm in thickness.Because of their chemical resistance, durability, and other properties, ceramic filters currently are used for various applications, one of which is in a water-purication device. The water paths of the filters are unidirectional straight channels, simply because they are produced by extrusion molding. Employing the AM techniques, however, enables us to make the channels more complicated, such as, for example, spiral channels as shown in Fig. 10 (a).[1][26] It will bring several potential benets including increase of contact area between water flow and the channel, local control of water ow (ow velocity, laminar ow vs. turbulence, etc.) and others, which may lead to improving the performance and miniaturizing the device. Figure 10 (b) shows an alumina filter model produced by PLM, containing spiral channels of 3 mm diameter, which can be identified from the traces of the cut model.[1][22] Similar filter models have been also manufactured by SLM, and the joining technologies for making a long-sized lter base are also under development.[26]Besides the above-stated ones, the HCMT project has manufactured several other types of prototype models, including artificial alumina knee joints whose internal surface has salient parts, which were difficult to make conventionally, to improve fixation into bones,[1][27] bone prosthesis with uniform pore size and no closed pores which leads to sucient inltration of bone cells and dense bones,[1][27] and ceramic cores for cooling systems of gas-turbine blades with remarkably shortened production time and wide exibility of the structure design.[1][28]Notable progresses have been made in direct laser sintering of ceramics as well.[1][29][30] A thin formed layer of alumina with high green density of 83 % has been successfully obtained by dewaxing and drying slurry layer containing Fig. 8 SiSiC exposure stage models for IC chip production(a) Conventional rib structure produced by molding approach, (b) PLM-produced rib structure having windows in the walls, and (c), (d) & (e) PLM-Produced truss structure of light weight/high stiness100 x 100 x 200 mm(e)200 x 200 x 40 mm(d)(c)(b)(a)200 x 200 x 80 mm200 x 200 x 30 mm

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