Ball End Magnetorheological Finishing Using Bidisperse Magnetorheological Polishing Fluid

A scheme to finish workpiece surface in nanometer range and obtain defect free surface using bidisperse magnetorheological polishing fluid (MRPF) by ball end magnetorheological finishing (BEMRF) tool is presented. Bidisperse MRPF consist of micron size CS and HS grade of carbonyl iron powder (CIP) with different volume fraction combinations within 20 vol.% magnetic solid contents, 25 vol.% SiC abrasives and 55 vol.% base fluid. Vibration sample magnetometer (VSM) has been used to study the magnetization of magnetic abrasives. Maximum magnetization has been found for CIP of 16 vol.% CS grade, 4 vol.% HS grade and 25 vol.% SiC abrasives. Magnetorheological behavior of bidisperse MRPF was evaluated using magnetorheometer. Performance of MRPF was evaluated by steady state rheograms in magnetic field strength. The yield strength of MRPF was found maximum at CIP of 16 vol.% CS grade, 4 vol.% HS grade, 25 vol.% abrasives and 55 vol.% base fluid. After characterization, experiments were performed with BEMRF tool on mild steel workpiece material for 30 min with given machining conditions. Percentage reduction in surface roughness (%ΔR a) was calculated and compared with %ΔR a obtained by finishing the workpiece with existing monodispersed MRPF and superior results as compared to existing one was found.