Parametric Analysis for Magnetorheological Finishing of External Cylindrical Surface of C60 Steel using Solid Rotating Tool Core

Abstract

A magnetorheological fluid based finishing process has been used to finish the external cylindrical surfaces at nano-level more efficiently. The existing MR finishing process based on stationary curved core tool tip is found comparatively less effective than the present process based on a rotating flat core tool tip for finishing the external cylindrical surfaces. This is due to the fact that in present process both workpiece and tool are rotating rather than giving rotation to the workpiece alone as in existing process. The carbonyl iron particles (CIPs) chains are rotated along with the rotation of the tool. This results in increase in kinetic energy of the active abrasive particles gripped by CIPs chains which causes for the better finishing performance. In preliminary experiment, finishing is done by both the tool tips namely, stationary curved core tool tip and rotating flat core tool tip. The final outcomes and results of the process using both these tool tips are compared. The Ra, Rq and Rz are reduced to 71.62%, 72.53% and 70.73% with stationary curved core tool tip, and 94.59%, 94.51% and 92.68% with rotating flat core tool tip in 90 minutes of MR finishing. The overall results revealed that the present developed process using rotating flat tool tip is more useful in finishing of external cylindrical surfaces as compared to the stationary curved tool tip. The shafts made of steel of grade C60 is taken as workpiece which finds application in manufacturing of various automobile components such as crankshafts, rocker arm shafts and rack-pinion power steering tie rods. In this research, detailed study through statistical design of the experiments is conducted by the developed rotating flat solid core based electromagnetic tool. Response surface methodology (RSM) has been used to plan and analyze the effect of current, tool rotational speed, workpiece rotational speed and abrasives concentration on percentage reduction in surface roughness (%ΔRa). The experimental outcomes are discussed and the finishing parameters are optimized to obtain the best finishing results. Analysis of the experimental data showed that the percentage reduction in surface roughness was highly influenced by the supplied current and tool rotational speed which are followed by workpiece rotational speed and abrasives concentration. This confirmed the significant role of tool rotation in present developed process for the excessive finishing performance which was not there in the existing nanofinishing process. The surface finish was obtained as low as 52 nm from the initial value of about 350 nm in 30 minutes of finishing time with the optimized parameters.