Numerical Analysis and Experiment on Effects of Spindle and Housing Shape Errors on Radial Error Motions of Aerostatically Supported Spindle

Abstract

Radial error motions of a spindle supported by an aerostatic journal bearing are investigated. The spindle units for analysis and experiment are consist of spindles having 0 lobe and 3, 5 and 9 lobes of 1.5 μm amplitude respectively and the housings having 0 lobe and 8 lobes of 1.5 μm amplitude respectively with two rows of 8 feed holes. The motion of the spindle is numerically solved with Runge-Kutta method and the force applied to the spindle is calculated by solving nonlinear unsteady Reynolds equation with FEM. The spindle motions are measured by capacitance type displacement transducers under free rotation, ranging 500 to 2500 min^-1. The numerical analysis program is verified experimentally for eight combinations of the spindle and the housing. It is shown analytically and experimentally that significant error motions occur, in particular, in the combinations of the 9-lobe spindle and the 0- and 8-lobe housings compared with other combinations.