Magnetorheological fluid based nanofinishing

Surface roughness of a manufactured part plays a vital role in improving the operative functionality of the product. Due to this there is an increasing demand for highly finished product (surface roughness of the order of nanometers) for their use in advanced engineering applications. Some of the industries that typically require these products are aerospace, automotive, optics, molds and dies manufacturing, etc. However it is not very easy to produce high quality surface by manual/hand polishing or conventional finishing methods. While manual finishing requires both skill and intensive labour, the available conventional processes like lapping, grinding, honing, etc. are limited by the fact that they produce sub-surface damage and residual stresses due to the high normal load associated with these processes. To overcome the above difficulties related to fine finishing several new magnetically controlled fluid-based finishing methods have been developed over the last two decades. However, while some of these processes lacked determinism in controlling surface topology others were not always capable of finishing complicated three dimensional (3D) surfaces. So a new ultra-precision finishing technology called the ball end MR finishing is developed for nanofinishing of 3D ferromagnetic and nonmagnetic surfaces. In this process, the smart characteristic of the magnetorheological polishing (MRP) fluid exploited at the tip of a rotating tool which moves over the surface profile to perform the finishing action. In operation it resembles a vertical milling process, with the ball shaped tip of magnetically stiffened fluid in place of the milling cutter. The ball end MR tool assembly is mounted on a five axis CNC setup to finish complex geometries of varieties of materials like steel, fused silica glass, silicon, polycarbonate, copper, aluminum, etc.