Magnetorheological Finishing (MRF) of a Freeform Non-magnetic Work Material

One of the newly developed methods for obtaining super-finished shiny surfaces for non-magnetic freeform jobs is magnetorheological finishing (MRF). MRF is an advanced finishing process in which the grinding force is controlled by magnetic field. The material removal in MRF is governed by the magnetorheological (MR) fluid which mainly consists of carbonyl iron (CI), abrasive particles, carrier fluids and additives. It is a precision-finishing process that can finish complicated geometries or difficult-to-approach regions. MRF process is capable of giving nanometre-scale surface finish. The process makes use of an MR fluid as a tool that acts as a flexible magnetic abrasive brush that provides finishing action. The relative motion between the finishing medium and the work can be obtained either by rotating the work, rotating the finishing medium or both. In the present paper, a set-up has been developed for MRF application using a pillar-drilling machine. Experiments were conducted to finish freeform jobs of copper alloy using the developed process. The effects of various process parameters, viz composition of the MR fluid, rotational speed of work and vessel containing MR fluid, mesh size of abrasives on surface finish, were explored.

Analysis of Surface Roughness and Surface Texture Generated by Pulsating Flexible Magnetic Abrasive Brush (P-FMAB)

The direct current magnetic abrasive finishing (DC-MAF) process provides practically no stirring effect on the static flexible magnetic abrasive brush (FMAB) formed by the magnetic field in the working gap. Absence of stirring leads to dullness of abrasive cutting edges in contact with the workpiece which results in a low finishing rate. To overcome this problem, the FMAB has been made pulsating using a DC-pulsed power supply, and the process is hence termed pulsed current-magnetic abrasive finishing (PC-MAF). The surface roughness was found to improve remarkably by the formation and destruction of the FMAB during the on and off time respectively, under selected pulsed parameters. The surface texture indicates that the process consists of microscratches generated on the finished surface. Further, the surface appears to have been generated by the removal of material from peaks of the workpiece surface by rotation as well as lateral movement of the FMAB.