Experimental investigation and machine parameter optimization for nano finishing of fused silica using magnetorheological finishing process

Abstract

Advanced optics design requires precise and super smooth finished glass surface. Most of the glasses that are used in the industries are Fused Silica, Bk7, Crown Glass and Boro-float glasses. Out of these, Fused Silica glass has a wide application in the field of optics. It has the capacity of withstanding and transmitting high energy laser pulses by limited absorption and having less deterioration to the material. It plays a major role, in the electromagnetic spectrum, specifically in the ultraviolet region. This paper describes about the non-conventional method of polishing technique. A sample of Fused silica glass has been considered and processed using Ball End Magneto rheological finishing method (BEMRF) with optimized machine and fluid parameters. This method has the capacity for polishing all sizes, shapes and types of materials. Advantage is that, subsurface damage can be minimized. This tool is being used for fabricating highly polished and precise optics. The increase in material removal with polishing time has resulted Fused silica glass sample with initial surface roughness of RMS 0.776 nm has been improved to RMS 0.257 nm by MRF polishing. Moreover, the surface roughness Ra has improved from the initial value of 0.594 nm to the final value of 0.165 nm. Further, the effect of polishing time on the volume of the material removal was also investigated. Based on the experimental results, the surface roughness and material removal are found as a function of the MR fluid condition and polishing time. Thus, angstrom level surface finishing on fused silica sample has been achieved by BEMRF technique.