Preliminary investigations into nano-finishing of freeform surface (femoral) using inverse replica fixture

It is difficult to achieve nano-level surface finish on freeform surfaces. Femoral (knee joint) is one of such components which has freeform surface. Finishing operations are very costly and time consuming. Surface finish of femoral plays a major role in its functionality, efficiency, and life expectancy. To have uniform (or minimum variation) surface roughness value along its curvature, an inverse replica of the femoral component as a fixture has been designed and fabricated so that the magnetorheological (MR) fluid velocity is approximately constant in different areas of the femoral. In this work, an attempt has been made for achieving comparatively more uniform finish on different surfaces and reducing the time required for finishing femoral. For this, a special tooling is used in rotational-magnetorheological abrasive flow finishing (R-MRAFF) process. Different extrusion pressures have been used to examine the effect on percentage change in Ra, finishing rate, and final surface finish of the femoral in both directions, X and Y. Minimum surface roughness of 78 and 89 nm has been achieved on femoral from the initial surface roughness of 172 and 178 nm in X- and Y-directions, respectively.