Effect of Variation of Gap Thickness of the Thrust Bearing on Gap Pressure and Stiffness of the Aerostatic Spindle in Vertical Milling

Abstract

When the partially porous aerostatic thrust bearing and the journal bearings of an aerostatic spindle in a vertical milling machine are subjected to cutting load and gravitational force, the thicknesses of gaps between the thrust plate and the spindle flange will change. This study applied CFD software to analyze the effect of variations of gap thickness and rotating speed on the pressure in the gaps of the bearings and the stiffness of the spindle. The results revealed that, when the thrust plate and the spindle flange were pushed back and forth by external loading, the pressure in the gap between the spindle flange and the thrust plate was affected significantly. The pressure in the gap between the spindle and the journal bearing was slightly affected. When the spindle rotated faster, the pressure on the surface of spindle became higher and the stiffness of spindle was increased.