Prediction Model for Edge Effects in Magnetorheological Finishing Based on Edge Tool Influence Function

In the optical manufacturing industry, magnetorheological finishing (MRF) is widely known as a deterministic process because of its subsurface damage removal performance and high-level performance of figure correction. However, similar to other optical manufacturing methods that belong to computer-controlled polishing, MRF faces the edge effect, in which the workpiece edge is rolled up or down. As the edge effect lowers the performance of optical components, it should be improved to ensure the final performance of the optical system. In this study, the edge tool influence function (TIF) obtained when the normal TIF was suspended from the workpiece edge was analyzed, and the distortion of the TIF occurring at the edge was explained. The edge TIFs with different overhang distances and polishing parameters, such as step height of raster scan path and swipe speed of TIF, were combined to present a new mathematical model for predicting the edge effect occurring after MRF. To verify the feasibility of the proposed prediction model, the edge effect generated by the uniform polishing of the entire surface of the electroless nickel was compared and analyzed with the edge effect predicted by the proposed model. The relative error of the edge effect generated according to the polishing conditions and the edge effect predicted using the proposed model was calculated to be 4–7%, and the validity of the proposed model was experimentally verified.