Theoretical analysis and experimental study of offset error of ultra-precision micro-spindle caused by cutting load

The existing ultra-precision micro-spindles fail to achieve the machining requirement of sub-micron precision because of its large radial error. In this study, the calculation model of radial offset error caused by cutting load is established for ultra-precision micro-spindle and an example design is carried out. The study finds that the offset of the tool tip increases with the increase of tool overhanging length and decreases with the increase of the span of spindle rotor. Bearing stiffness has the greatest effect on the tool tip offset, followed by the tool deflection deformation while the deflection deformation of spindle rotor has the smallest effects on the tool tip offset. The thrust bearing restrains the increase of tool offset error to some extent. The supporting centre of the aerostatic bearing shifts under the acting of cutting load due to its small bearing stiffness. Finally, the testing was conducted on a prototype micro-spindle, which shows the rationality of the established model.