Through studying the porosity of the ceramic parts fabricated with slurry-based rapid prototyping process of ceramic laser fusion and ceramic laser sintering, the feasibility of directly fabricating ceramic shell mold was investigated in this paper. Although the total porosity of the fusion part was low, microcracks led to low strength, which was hardly enhanced by post-treatment of infiltration. On the other hand, by adjusting the slurry formulation and varying the laser scanning energy, the open porosity of the sintered part was over 90 vol.% of the total porosity. High open porosity resulted in good permeability, which is one of the important characteristics of the ceramic shell mold for investment casting. To verify the feasibility of producing casting part with ceramic shell molds fabricated by the processes of ceramic laser fusion and ceramic laser sintering, the casting process was conducted to obtain the casting parts.

Based on ceramic laser gelling process, the purpose of this research is to obtain a proper slurry, which can be employed to cast layer with a thickness smaller than 100 μm to improve the staircase effect occurred in layer manufacturing, by optimization of the water content to fabricate ceramic part with better surface. The slurry was composed of alumina particles with average size of 0.5 μm as the structure element, silica sol as an inorganic binder and ammonium polymethacrylate as a dispersant. The slurry was dispersed uniformly by a ball mill. The results revealed the variation of water content will significantly influence the viscosity of the slurry and the formability of the ceramic green part. High water content led to poor binding of the particles and induced the delamination of the consolidated layers. On the contrary, low water content led to high shear force between scraper and slurry surface; such force damaged the previous layer during the casting process. As a result, the water content of 34 wt% was the most favorable to casting thin layers. The capability of casting 40 μm layer, which is smaller than that obtained by previous studies, was achieved. Because of the thinner layer, the staircase effect was improved.

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