Improving waviness in ultra precision turning by optimizing the dynamic behavior of a spindle with magnetic bearings

The aim of this paper is to present an approach of improvement of the surface flatness in diamond turning with a spindle on magnetic bearings. The procedure followed to attenuate the defect involves two processes of dynamic compensation of the spindle parasitic movements: (i) the classical dynamic balancing of mainly the tilting motion; (ii) the more specific active compensation of the non-linear components of the spindle movement by minimization of the harmonics of the spindle displacements synchronous with the frequency of rotation. Surface analysis at each step shows that the evolution of the surface figure is closely correlated, at a scale of some nanometers, with the dynamic movements of the spindle, and may consequently be significantly attenuated with an active compensation.