Progress Update in Magnetorheological Finishing

In magnetorheological finishing (MRF), magnetically stiffened magnetorheological (MR) abrasive fluid flows through a preset converging gap that is formed by a workpiece surface and a moving rigid wall, to create precise material removal and polishing. Theoretical analysis of MRF, based on Bingham lubrication 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 is obtained. A unique attribute of the MRF process is its determinism. MRF has been successfully implemented to polish optical surfaces to very high precision. MRF reduces the surface micro roughness of optical materials to ≤ 10A. Figure errors are corrected to a fraction of a wavelength of light and subsurface damage is removed. A wide range of optical surface shapes, including aspheres, has been polished on many different materials. Other applications in precision finishing are being considered, including integrated circuits and advanced ceramics.