Influence of Unbalanced Electromagnetic Force and Air Supply Pressure Fluctuation in Air Bearing Spindles on Machining Surface Topography

Abstract

Air Bearing Spindles (ABS) can meet high accuracy demands for the precise rotation motion, which adopt air bearings to support spindle shaft, and the spindle shaft directly connects the motor rotor. The unbalanced electromagnetic force caused by motor rotor eccentricity (MRE) and air pressure fluctuation (APF) are two important influential factors to the dynamic performance of the spindle system and machining surface quality. This paper addresses the problems of measuring the MRE and APF in an ABS through testing machining surface topography. A permanent magnet synchronous motor (PMSM) was modelled by finite element simulation (FES). Through FES it found that the MRE between the motor rotor and stator hole produced a Radial Magnetic Force (RMF), which could cause ABS to periodically vibrate in the axial direction. Besides, the change of the air supply caused the stiffness variation of ABS and result in the tilt error motions of the spindle shaft. A theoretical model of machining surface topography considering MRE and APF was then proposed for the first time, which revealed that the MRE and APF resulted in the periodic fluctuations of the machining surface topography. The overall surface topography then became grooved surfaces. The above findings were finally validated by measurement results of ultraprecision diamond turning experiments.

Integrated design and analysis of a high-precision aerostatic spindle for internal grinding machines and its implementation perspectives

“…In ultra-precision spindle systems, the spindle characteristics at various scales correspond to the machining errors at various scales of sub-micron shape error and nanoscale surface roughness. Research has focused on the influence of the air film geometry 1,2 and dimensional parameters 3,4 at the microscopic level as well as the air supply pressure 5 on essential bearing performance parameters: load capacity, stiffness and mass flow rate. 6,7 Chen et al 8 examined the major requirements in the design of the number and arrangement of the aerostatic bearings orifice for spindles operating at either low or high speeds.…”

Multi-Field Coupling Dynamics Modeling of Aerostatic Spindle

“…During the operation of the aerostatic spindle, it shows the multi-physics field coupling characteristics, in which the coupling effect of air bearing, the shaft and the motor should be considered for fully understanding its dynamics behavior [ 4 ]. However, the previous literatures commonly focused on single factor or two factors while investigating the dynamic characteristics of the aerostatic spindle [ 5 , 6 , 7 , 8 ]. It has been pointed out that the existence of unbalanced magnetic force (UMF) caused by rotor eccentricity at the motor can have a considerable impact on the machined surface [ 9 , 10 , 11 ], thus, the electromagnetic factor is not negligible in the dynamics model of aerostatic spindle.…”