Progress update in magnetorheological finishing

In magnetorheological finishing (MRF), magnetically stiffened magnetorheolo gical (MR) abrasive fluid flows through a preset converging gap that is for med by a workpiece surface and a moving rigid wall, to create precise mater ial removal and polishing. Theoretical analysis of MRF, based on Bingham lu brication theory, illustrates that the formation of a core attached to the moving wall results in dramatically high stress on the workpiece surface. A correlation between surface stress on the workpiece and material removal i s obtained. A unique attribute of the MRF process is its determinism. MRF h as been successfully implemented to polish optical surfaces to very high pr ecision. MRF reduces the surface micro roughness of optical materials to le ss than or equal to 10A. Figure errors are corrected to a fraction of a wav elength of light and subsurface damage is removed. A wide range of optical surface shapes, including aspheres, has been polished on many different mat erials. Other applications in precision finishing are being considered, inc luding integrated circuits and advanced ceramics.