An evaluation system for surface waviness generated by the dynamic behavior of a hydrostatic spindle in ultra-precision machining

The generation mechanism of the surface waviness, influenced by the dynamic behavior of the hydrostatic spindle system, is critical for evaluating the machining accuracy of a machine tool. In this study, an evaluation system is proposed to identify the key parameters of a shaft supported by the hydrostatic bearings and to decide the order preference of the influencing factors in the spindle system. The balance analysis is performed to describe the key parameters; then, the generation model of the waviness is built up according to the spindle vibration information. The relationship between the generation model and the actual waviness results is evaluated through the correlation method. It is found that the degree coefficient is above 0.45. Finally, the corresponding spectral characteristics of the spindle system are extracted from the actual waviness results with power spectral density. This verifies that the spindle error is the main factor affecting the accuracy of the actual machining; furthermore, the generation model of the waviness under the effect of the spindle error is correct.