Predicting the effect of vibration on ultraprecision machining surface finish as described by surface finish lobes

Surface finish error resulting from unwanted relative tool/workpiece harmonic motion in the in-feed direction is studied for the ultraprecision face turning operation. Specifically consideration is given to the manifestation of this motion in the feed direction of the workpiece for a broad range of relative tool/workpiece motion disturbance frequencies. The concept of surface finish lobes is presented and is used to describe the feed direction surface finish error spatial frequency expected on a workpiece surface, for a given disturbance frequency. The surface finish lobes make it possible to know, for a broadband of disturbance frequencies, the resulting error on the workpiece surface in the feed direction. The surface finish lobe methodology is validated with experimental findings. Finally, potential applications of the surface finish lobes are discussed, including their use in shifting waviness errors to a very long wavelength, thus reducing the impact of unwanted relative tool/workpiece harmonic motion on ultraprecision machining quality.