Effect of motor rotor eccentricity on aerostatic spindle vibration in machining processes

Abstract

In ultra-precision machining field, the air motorized spindle which is composed of a motor and an air bearing, plays a major role. In air motorized spindle, the motor eccentricity between the stator and the rotor is inevitably introduced during the manufacturing process, which directly affects the machining results of workpiece surface, and this phenomenon is particularly unwanted in machining. However, little attention has been paid to the motor eccentricity of air motorized spindle. In this paper, a new integrated electromechanical coupling method for estimating unbalanced force in air motorized spindle is presented, and the effects of motor rotor eccentricity on surface topography in ultra-precision processes are analyzed. An electromagnetic-mechanical method is used to study the coupling effects between the motor rotor and the aerostatic spindle. Meanwhile, the motor rotor and the aerostatic spindle are analyzed as a whole. In order to clearly describe the electromagnetic–mechanical method, the ultra-precision spindle for potassium dihydrogen phosphate crystal machining tool is selected as the research object, and the model of air motorized spindle and motor rotor eccentricity are presented. Besides, in order to assess the impact of the radial magnetic force caused by motor rotor eccentricity on the spindle performance, a range of rotor eccentricities is calculated. Additionally, the influence of the motor rotor eccentricity on the dynamic response of spindle is further analyzed. It is found that motor rotor eccentricity has a significant influence on the spindle vibration, which dramatically reduces the processing quality. Finally, the machining experiments are carried out, and the flatness errors of the workpiece caused by the motor rotor eccentricity are obtained by the wavelet method. The experimental results are consistent with the analysis results, which verifies the reliability of this method. This study is quite meaningful for deeply understanding the influence of motor rotor eccentricity on the machined surface.

Multi-Physics Fields Based Nonlinear Dynamic Behavior Analysis of Air Bearing Motorized Spindle

“…By integrating the flux density along the surface of the rotor, the UMF can be obtained. Wang et al [29] pointed out that the UMF increases almost linearly with the eccentricity which was also proved by Wu et al [32]. However, the rotor eccentricity in their research is at the motor which is much larger than the eccentricity at air journal bearing, it means the variation of the UMF may not vary linearly at small eccentricity.…”

“…Xu et al [31] investigated the influence of the UMF to the dynamic behavior of motor rotor, the limit cycle with and without unbalanced mass was analyzed. Wu et al [32,33] investigated the UMF in the ABMS and its effect on surface generation in turning which stressed the underlying significance of electromagnetic factors of the ABMS. From the previous research, the influence of electromagnetic factors on the dynamic behavior of the ABMS remains to be further explored, especially when considering multiphysics fields.…”

Electric-Magnetic-Mechanical Coupling in Precision Machines

“…However, little attention has been paid to the motor eccentricity of air motorized spindle. Wu (Wu et al 2018) presented a new integrated electromechanical coupling method for estimating unbalanced force in air motorized spindle, and the effects of motor rotor eccentricity on surface topography in ultraprecision processes are analyzed as shown in Fig. 14. By optimizing the dynamic performance of the spindle with magnetic bearings, there are two coupling factors to improve the waviness of ultra-precision turning effects.…”

Linear forced-rotordynamics analysis for optimizing the performance factors of machine motorized spindle using design explorer method

“…Zhou et al [5], conducted a study on motor-rotor unbalance effects for identifying damping and stiffness coefficients of closed-loop active-magnetic-bearing. Wu et al [6], comprehensively introduced the influences of motor-rotor eccentricity on surface topography in ultra-precision machine, by using a new integrated electromechanical coupler manner for estimating unbalanced force in air-motorized-spindle. In MMS design, there are many factors influence its dynamic performance; so, it important to define the levels of these factors in design stage.…”