Magnetorheological abrasive honing (MRAH) is a recently developed process that makes use of magnetically stiffened abrasive-mixed magnetorheological fluid and combined rotary and reciprocating motions to finish engineering surfaces.Magneto-rheological abrasive finishing is a non-traditional method of improving the surface finish of manufactured components. Performance of different variants of this finishing process in terms of surface roughness parameters and material removal with process variables have been reported in the literature.
History
Most of the finishing processes are pressure or force controlled, as against the surface or cylindrical grinding processes which are displacement controlled. In all cases, the process leaves its signature on the surface. Classical examples of pressure-controlled finishing processes are honing, lapping and super-finishing. In the last few decades, attention of researchers has turned towards non-traditional methods of finishing the surfaces. One such process is magneto-rheological abrasive finishing in which abrasive mixed with magneto-rheological (MR) fluid is used. Kordonski and Jacobs (1996) developed a setup in which magnetically stiffened magneto-rheological fluid mixed with abrasives is made to flow over a moving flat rigid wall and the polishing happens at a converging gap formed by the surface to be finished and a moving wall. Now it finds an interesting industrial application in polishing of optical lenses. The major advantage is that the abrasive medium exhibits higher yield strength when subjected to increased magnetic field. Apart from the ways of introducing the abrasive mixed MR fluid, the relative motions between the work piece and abrasive medium are imparted in different ways; using reciprocation, rotation or combination of both. Reciprocation motion has been employed in magneto-rheological abrasive finishing by Jha and Jain (2004). Seok, et al. (2007) employed MR fluid alone for the fabrication and finishing of curved silicon-based micro-structures. While Sadiq and Shunmugam (2009a,b) used both reciprocation and rotation, Dass et al. (2010) later investigated the process with rotary motion imparted to the abrasive medium by rotating magnetic field. In general, researchers working with MR fluid based finishing processes have studied the improvement in surface finish with process variables such as abrasive size, abrasive concentration, magnetic strength, reciprocation speed, rotational speed and processing time, taking work pieces with different initial roughness. Many results have been published mainly on surface finish improvements in terms of Ra and subsequently the study has been extended to include Rmax, Rz , etc. It is interesting to note that these parameters, characterizing the profile in the height direction, are derived from the same profile and hence are correlated. These roughness parameters do not reveal the nature of the profile and the changes happening to it with time for a given set of process parameters. Studies on material removal during the magneto-rheological abrasive finishing have also been reported. The metal removal is measured by weighing the work piece before and after processing.