Abstract: Hydrostatic spindles are core components of high precision machine tools, which have been widespread used in mechanical engineering, but the mechanism of rotation error has not been revealed clearly. According to current documents and models, the transient processes of the spindle from an equilibrium position to a dynamical orbit could not be simulated quantitatively. The intrinsic relationship among the disturbance factors, the position, the flow and the oil film force could not be revealed, as resulted in that the mechanism of the rotational error motion of hydrostatic spindle could not be described exactly. The dynamic model of the rotation error motion of hydrostatic spindles is established. Three methods, which are full process moving mesh method, equilibrium position & moving mesh method, and equilibrium position & simplified formula method, are used to quantitatively calculate the trajectory of a spindle from the concentric position to forming rotational error. The inherent laws among the disturbance factor, total force, the flow and the position are discovered. The rotation error is evaluated by using of the Least squares method. By studying the influence of these three calculation methods on the rotary centre position and rotary error, the reasons that results in calculation difference are found. The method which combines the moving mesh method and the simplified formula to calculate the rotary accuracy of hydrostatic spindle are verified to be efficient and pinpoint.

Key words: hydrostatic spindle;rotation error;dynamic mesh method;ultra-precision machine tools