Vol.11 No.2 2018

報告:Additive manufacturing of ceramic components (大司)−90−Synthesiology Vol.11 No.2(2018)200 x 200 x 80 mm(a)(b)(c)(a)(b)3 mmΦ Spiral channels80 mmL x 30 mmΦCut modelComplicated structures,e.g., spiral channelsConventionalstraight channelsFig.10 (a) Conventional water-purification ceramic filter has unidirectional straight channels, while the AM techniques enable more complicated channels, e.g., spiral ones. (b) an alumina lter model produced by PLM, containing spiral channels of 3 mm diameter whose traces are observed in the cut modelFig. 9 (a) Conventional rib structure, (b) Optimal rib structure obtained by computer simulation based on structural topology analysis, and (c) an SiSiC exposure stage model (green body) produced by PLM based on the structure (b)optimal mixture of dierent sorts of alumina powder. Laser-irradiating this highly-packed green alumina layer has led to full densication without such glassy parts, unsintered ones, and cracks as reported previously.[21] The laser absorption coecient was adjusted by using a proper amount of material having a dierent coecient from alumina.6 Summary and future perspectivesThis article describes the R&D strategies and the current achievements on AM of ceramics in the HCMT project, which has been initiated since 2014. The two AM technologies, PLM and SLM, which are advantageous in terms of dimensional accuracy, shape-flexibility, density-controllability, etc., are being developed for producing ceramic green bodies. A variety of 3D prototype models for varied target products have been manufactured so far by using the developed AM technologies. Furthermore, intensive research eorts are being devoted to ceramic laser sintering. In order to ensure the developed technologies, 7 and 26 patents have been applied for on PLM and on the HCMT project as a whole, respectively, as of March, 2018.While AM of ceramics has numerous advantages as already stated, there are also several issues which should be taken into consideration when using it for industrial applications: (1) Profitable almost only for large variety-small amount products, (2) Facilities sometimes can be very expensive, requiring substantial initial costs, (3) Difficult to apply to ceramics, for which melting and solidification are not available in principle, (4) Currently usable only for producing green bodies, which are to be post-sintered in a conventional furnace, (5) Whether AM products give us the same properties as those of conventional ones is not certain, (6) Some restrictions apply to powder used, e.g., the grains should be free owing, requiring a preferably spherical shape and size of ~50 µm when supplying them to the forming stage in some methods including binder jetting and powder bed fusion. In order to overcome these issues and establish AM as manufacturing technologies in ceramic industry, further R&D eorts are critically required in the future.

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