Design Considerations of Nanometer Resolution Aerostatic Spindle Bearing for Ultra Precision Machining

The paper addresses the key design considerations for aerostatic bearings for ultra precision machines requiring nanometer precise spindle rotation and moderate axial and radial stiffness. The development in optical & opto-electronic industry, defence, space and nuclear research demands for high form less than 0.1 μm and surface finish in the order of 2-5 nm components to be used as optics. Aerostatic bearing spindles with nanometric accuracy are required to manufacture such high precision optics. Many research and developmental work has been carried out for the past three decades in the field of aerostatic bearing design and performance testing. The selection of suitable bearing type and configuration plays a critical role in achieving the spindle running accuracy in nanometre range. This paper focuses on the selection criteria of bearing film thickness, air bearing types and configurations, air inlet feeding media, and the material selection. The errors associated with the aerostatic bearings and its effect on the surface finish and form accuracy of the component is also discussed in the paper. This gives a clear and basic insight to designers to begin with the aerostatic bearing spindle design for ultra precision machines.