A Thermomechanical Model of Machine Tool Spindles for Use in the Design of Reconfigurable Angular Contact Spindle Bearing Load Control Systems

Thermally induced bearing loads have long been recognized as a key factor impacting the reliability and performance of machine tool spindle systems. This is particularly true for reconfigurable machine tool spindles which may experience a wide range of external loads, processes and spindle speeds. Recent research on a roller bearing spindle has shown that it may be possible to control these loads by controlling the temperature distribution within the spindle housing. As this research focused on thermally induced loads in roller bearings, the bearing load model used was largely limited to a radial heat transfer/thermal expansion model. The purpose of this paper is to present a first step model for developing a methodology for designing bearing load monitoring and control systems for reconfigurable angular contact bearing spindles. The proposed model focuses on the thermally and mechanically induced spindle bearing loads in a back to back angular contact bearing pair that are due to radial and axial thermal expansion as well as the centrifugal forces and moments of the bearing balls. Simulation results demonstrate that the proposed model is capable of predicting the interactions between bearing loads and spindle deflections that are likely to be important in the design of future reconfigurable machine tool spindle bearing load monitoring and control systems.