Parametric study on influence function in magnetorheological finishing of single crystal silicon

Abstract

Magnetorheological finishing (MRF), a precision polishing process, becomes an integral part of optics manufacturing industries for its ability to improve figure and surface finish of complex shape optics without introducing surface damage. It employs magnetically stiffened magnetorheological fluid (MR) ribbon as a flexible polishing tool which moves through the converging gap against workpiece. Material removal characteristic of a polishing tool is described as influence function. Influence function is a parameter to evaluate the efficiency or effectiveness of the polishing process. It provides some useful information for setting up appropriate process parameters to finish different surfaces. Rotational speed of the carrier wheel and gap between the workpiece and magnet are the selected process parameters for studying the influence function. The spot (or influence function) profiles are analyzed to calculate the volume of material removal and depth of the deepest penetration (ddp) using 3D noncontact profilometer. The maximum contribution is made by wheel speed on the volume of material removal and depth of the deepest penetration. To observe the effect of selected parameter setting on the surface topography, final experimentation is performed by employing longitudinal and cross feed and it is perceived that surface generated by cross feed is more uniform.