Automated insular surface finishing by ball end magnetorheological finishing process

Abstract

ABSTRACT Ball end magnetorheological finishing (BEMRF) is a process employed for precision finishing of flattened, intricate form complex 3D surfaces up to the nano level. Roughness of a surface determines the quality of results produced, which is usually measured by stylus-based instruments, with some optical methodologies also being adopted. These conventional methods when used for BEMRF tend to introduce errors in the part, which have to be removed from its fixture for measurement, and it is not feasible to remount it in the exactly same orientation again. Applications such as insular finishing (i.e., confined to a narrow region on the workpiece) demand the workpiece to be kept in the same orientation throughout, leading to requirement of measuring roughness in situ during the BEMRF process. A confocal sensor fits the requirement because of its confined design and lightweight capabilities. This work presents integration of a confocal sensor into the BEMRF setup for in situ roughness measurement. An initial Ra value of 352 nm was reduced to 289 nm just by insular finishing before finishing the full surface down to 78 nm in the case of a grinding error, from 420 nm to 342 nm by insular finishing, and finally down to 142 nm in the case of lapping error.