Abstract
The spindle is a vital component of machine tools. In particular, the ultra-precision machine tool equips the precision spindle system, hi general, the precision spindle uses hydrostatic bearings for achieving precise rotational motion. An important performance index of the hydrostatic bearings is the bearing stiffness. In many design cases of the hydrostatic bearings, however, actual bearing stiffness of the fabricated bearings becomes smaller than that of design. Our previous reports indicate that the pressure of the lubricant fluid deforms the parts of the spindle that changes critical dimension of the bearings such as bearing gap. This report thus investigates the influence of the fluid pressure on the bearing stiffness. In particular, the paper considers the influence of the deformation on the stiffness when the spindle rotor moves due to the external loads. The FEM analysis and numerical calculation reveal that the influence of deformation reduces the bearing stiffness by about 10%.
