Development of New Magnetorheological Fluids for Polishing CaF2 and KDP

LLE Review, Volume 80 213 Magnetorheological finishing (MRF) is a novel and recently commercialized1 process for figuring and polishing plano, convex, and concave optics—both spherical and aspherical— from a wide variety of optical materials. A recently written review article provides an overview of the history, theory, and implementation of this technology.2 The utility and productivity of MRF have been proven for a wide spectrum of optical glasses and demonstrated for a variety of non-glass optical materials.3,4 A 1.0-nm smoothness with removal rates of 1 to 10 μm/min is routinely achieved. Seven years of research and development culminated in 1998 with QED Technologies’ introduction of a commercial MRF machine, designated the Q22. A focus of continuing research is the development of MR fluid compositions and operating parameters to finish optical materials with an ever-widening range of physical properties. Efforts are simultaneously made to extend our understanding of the fundamental mechanisms of material removal in the MRF process. Extremely hard, extremely soft, single-crystal, polycrystalline, or water-soluble optical materials—each presents unique challenges to the MRF process.