Reducing the error motion of an aerostatic journal bearing

This paper reports on the design and experimental validation of an ultra-precision air bearing rotary system, intended to reduce the radial error motion, i.e. the deviation from perfectly centric motion, to a nanometre level (< 10 nm). To this end, the influence of several bearing parameters on the radial error motion of an aerostatic journal bearing is analysed, which leads to the formulation of several design guidelines. Increasing the number of feedholes proves to be a promising solution. As a limit case of infinite number of feedholes, the radial error motion of a porous aerostatic journal bearing is analysed and experimentally validated by the means of a porous aerostatic rotary table. Recent experiments show a synchronous radial error motion of 11 nm for the porous aerostatic rotary table under test.