Theoretical and experimental investigation of spindle axial drift and its effect on surface topography in ultra-precision diamond turning

In ultra-precision diamond turning (UPDT), the spindle axial drift directly affects the machining accuracy. Due to the difficulty of measuring the spindle drift during the machining process, the spindle axial drift was rarely studied. In this paper, an experimental method is used to prove and measure the existence of the spindle axial drift at the machining process, and the influence of spindle drift error on the machined surface is further studied. A mechanical model of the spindle system is considering the mass eccentricity, and the dynamic behavior of the spindle in working conditions are simulated with the mathematical model. Periodicity whirl of the spindle is found in the simulation, which is verified by the end face turning experiments. Then, the influence of the spindle vibration on surface topography is discussed, considering the spindle rotation speed and its dynamic balance. Meanwhile, the vibration frequencies induced by the spindle rotation are detected by the signal analyzer, and the detected frequency has been found to agree well with the experimental wave period of the workpiece surface (WS). This study is quite meaningful for deeply understanding the influence rule of spindle unbalanced error from the viewpoint of machined surface and vibration frequency. The research results are useful for the spindle error control and machined surface error prediction.