An LDV-based methodology for measuring axial and radial error motions when using miniature ultra-high-speed (UHS) micromachining spindles

This paper presents a laser Doppler vibrometry-based methodology for measurement of axial and radial error motions when using miniature ultra-high-speed (UHS) spindles used for micromachining applications. The new methodology measures three-dimensional displacements from the surface of a custom-fabricated sphere-on-stem precision artifact using three mutually orthogonal laser beams. A precision alignment technique is developed to configure the three laser beams mutually orthogonal to one another. An infra-red sensor is used to provide a reference for the rotational angle of the spindle. The axial and radial motion data measured at operational speeds is then post-processed to obtain the synchronous and asynchronous components of the error motions in both directions. The presented approach enables obtaining error motions along both fixed-sensitive and rotating-sensitive directions. The methodology is then demonstrated by measuring axial and radial error motions when using a miniature ultra-high-speed spindle at four different speeds. Analysis of the measured data indicated the significant effect of spindle speed on the error motions along both fixed-sensitive and the rotating-sensitive directions. Finally, an uncertainty analysis is presented to quantify the overall combined uncertainty on the error measurements when using the new methodology.