Static characteristics of aerostatic guide made of partially porous ceramics

Abstract

While both friction and wear are small in an aerostatic guide whose bearing surfaces are separated by an air film, the stiffness is rather small. Porous materials are frequently used as a restrictor to improve stiffness in an aerostatic guide. In this study a partially porous ceramics, whose boundary between the porous part and the fine part was seamless and of which the porosity and the pore size were able to be controlled flexibly, was applied to the aerostatic guide. The fundamental static characteristics of the aerostatic guide made of the partially porous ceramics were evaluated. In addition, electroless plating was posited onto the porous ceramics surface for the purpose of obtaining high static stiffness, and the effect of plating on the static stiffness was examined. The influence of deflection of porous ceramics on static characteristics of aerostatic guide was also evaluated. The minimum clearance at the maximum dimensionless static stiffness varied little with the deflection of porous ceramics. The maximum dimensionless static stiffness was decreased by the deflection of the porous ceramics. The maximum dimensionless static stiffness could be evaluated with the ratio of the deflection to the apparent clearance. Even in the case of the non-plated ceramics, the maximum dimensionless static stiffness was around 0.4. In the case of the plated ceramics, the flow rate decreased by 1/10 or less and the clearance decreased by approximately 1/3. Consequently, high stiffness was obtained by the plating. The partially porous ceramics employed in this study would be able to be applied to aerostatic guides.