Hydrostatic machine tool spindles

Abstract

This work investigates the application of hydrostatic bearings, particularly those of the self-compensating type, to precision machine tool spindles. First, relations are developed that can be used to calculate the hydraulic resistances of various bearing land flows in tilted and untilted orientations. These relations are then applied to predicting the load carrying characteristics of several different types of hydrostatic bearings. The bearing calculations are then integrated with shaft bending calculations to predict static spindle stiffness. Relations are also presented to calculate the frictional and thermal characteristics of the bearings at high speeds. The relations developed are compared to experimental data collected on three prototype test spindles. These spindles were found to have excellent qualities that represent a significant advance in machine tool spindle technology. Finally, a design case study is presented that illustrates how the methods developed in this work may be applied to practical spindle design.