Investigation of ripple phenomenon in hybrid grooved aerostatic bearings

Thrust aerostatic bearings with groove restrictors are major types of supporting components for ultra-precision machine tools and metrology instrument due to their high motional accuracy when moving in a high speed. Ripple is an undesired phenomenon occurred during bearing operation which will reduce the attainable motional accuracy. In this paper, a rapid iterative algorithm based on the resistance network method (RNM) and flow-difference iteration method is proposed to efficiently model and predict the static parameters and the ripple phenomena in the linear grooved (LG) and crossed grooved (CG) thrust aerostatic bearings. The accuracy of the theoretical prediction model is verified qualitatively by computational fluid dynamic (CFD) simulation. It is clearly demonstrated that the ripples of LG and CG thrust aerostatic bearings occur under specific processing parameters at the film thickness of the maximum stiffness. Theoretical modelling and CFD simulating approach for prediction of undesired ripple phenomena is crucial to realize the targets of nanometre or even sub-nanometre positioning accuracy of air bearing supported ultra-precision motional stages.