Nanofinishing of Fused Silica Glass Using Ball-End Magnetorheological Finishing Tool

Abstract

The surface finishing of fused silica in nanometer range and in obtaining defect-free surface is a challenge and in high demand because of its applications for transmitting high energy laser pulses. A novel nanofinishing process using ball-end Magnetorheological (MR) finishing tool was developed for finishing of flat as well as three-dimensional (3D) surfaces of ferromagnetic and non-ferromagnetic materials. In this process, a magnetically controlled ball end of smart MR polishing fluid is generated at the tip of the cylindrical tool, and it is guided to follow the surface to be finished through computer controlled three-axes motion. The process is automated and used for finishing precise components in manufacturing system. The smart behavior of MR-polishing fluid is utilized to precisely control the finishing forces which exhibit change in rheological behavior in the presence of external magnetic field. The finishing of fused silica glass was done using cerium oxide Cerox 1663 abrasive powder. The effect of finishing time on final surface roughness was studied, and the finished surfaces were observed under atomic force microscope. Significant improvement in surface roughness (Ra), root mean square (RMS), and Rmax value has been obtained after 90 min of finishing. Ra as low as 0.146 nm was achieved from initial value of 0.74 nm.