Feasibility study of the novel quasi-elliptical tool servo for vibration suppression in the turning of micro-lens arrays

In fast or slow tool servo (F-/STS) diamond turning of micro-lens arrays (MLAs), the inherent non-smooth servo motion will lead to undesired tool vibrations, and it can significantly deteriorate the quality of the machined surface. Starting from a mathematical explanation of the underlying mechanism for vibration suppression, a quasi-elliptical tool servo (QETS) technique and the corresponding optimal toolpath determination algorithm are proposed to overcome the inherent defects in F-/STS turning of MLAs. As for the QETS, the inherent non-smooth servo motion in the F-/STS is proposed to be decomposed into two smooth quasi-harmonic motions along the cutting and servo motion directions, which then constructs the quasi-elliptical trajectory. Taking advantage of the smooth nature of the two decomposed motions, the undesired tool vibrations induced by the motion nonsmoothness in the F-/STS can be significantly eliminated, accordingly facilitating the generation of MLAs with homogeneous and smooth surfaces. Finally, the new concept is verified through numerical simulation of the tool motion and experimental demonstration by turning a typical hexagonal aspheric MLA.