Vol.11 No.2 2018

報告:Additive manufacturing of ceramic components (大司)−85−Synthesiology Vol.11 No.2(2018)sintering, etc.), resulting in the sintered density of 84 %, without the additional treatments, in a simple-shaped alumina plate (50 x 50 x 5 mm) for specific mixed powder and experiment conditions.[20]Figure 4 shows SLM’s procedure, which includes the following: (1) Mixing fine ceramic powder and liquid photopolymer and putting them into the slurry supply, (2) Supplying the mixed slurry from the slurry supply on the substrate and smoothing them using a knife edge for forming a thin layer (typically several 10 µm), (3) Curing the photopolymer by laser light for the desired part, (4) Lowering the substrate by the formed layer thickness, followed by the same remaining processes as PLM (5, 6). SLM is a wet approach and therefore has characteristics totally opposite to PLM; due to the high fluidity, it is advantageous for producing dense parts of complex-shapes with high precision. It has been reported that careful selection of raw powder in SLM of alumina resulted in a high sintered density of 99 % with a bending strength of ~800 MPa.[14] On the other hand, undesired deformations and distortions often are generated during the drying process, which leads to unsuitability for making large-sized products. Therefore, the HCMT project is aimed at avoiding such deformations and distortions by optimizing the processing conditions and modifying the forming apparatus. It is also critically important to disperse the ne ceramic particles densely into the slurry, for example by using ceramic powder having bi-modal size distribution, with sucient degassing for reducing sintering-shrinkage as well as obtaining dense bodies.As stated above, it is extremely difficult to obtain sintered bodies by directly laser-sintering ceramic powder in AM. For example, Qian, et al.[21] investigated direct-laser-sintering of alumina, and revealed three detrimental phenomena in the sintered body including glassy parts due to overheating/rapid cooling, unsintered parts due to heat lack, and cracks due to thermal stress. If it is realized successfully, however, it will bring enormous benets of savings in the post sintering process which needs substantial cost and time. The HCMT project, therefore, also deals with direct laser sintering of oxide and non-oxide ceramics (CLS); the approach includes full-packing ceramic powder in a layer, optimizing laser irradiation conditions for critical temperature control, etc.4 Platform technologies in PLMFor optimizing AM procedures of ceramics, there are a number of technical items that should be carefully examined and properly selected. This chapter discusses what sorts of technical items there are, how they are connected and correlated to each other and what should be considered and Fig. 3 Typical forming procedure of powder-layer manufacturing (PLM). The number in parenthesis corresponds to that of the description in the text. Fig. 4 Typical forming procedure of slurry-layer manufacturing (SLM). The number in parenthesis corresponds to that of the description in the text.Powder SupplyPowder SupplySqueegeeForming stagePowder supplyPowder supplyLaser heatCeramic powderPolymerbinder(1)(2)(3)(4)(2)(2)Knife edgeForming stageSubstrateLaser lightCeramic powderLiquid photo-polymer(1)(2)(1, 2)(3)Slurry supply(4)

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