Nanofinishing of freeform surface using magnetic field assisted finishing (MFAF) process

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Now-a-days freeform surfaces are frequently used in different industries due to its usefullness. Finishing of freeform surface is a challenging and a complex task. In medical industry, surface of femoral component of a knee joint implant is fabricated freeform shape to increase the resemblence between actual human knee movement and the artificial one. Magntic field assisted finishing (MFAF) process is used to counteract the problems faced during finishing of femoral knee implant and to provide required uniform surface roughness and charaterstics. A novel MFAF polishing tool is designed and developed. As the polishing tool is newly developed, hence its capability to finish Ti alloy for biomedical application is explored in the present study. Also, the competency of the developed tool to finish freeform surface is investigated. This process uses magnetorheological (MR) polishing fluid whose rheological behaviour is controllable by external magnetic field. Two type of MR fluid is synthesized to generate required surface for biomedical application on Ti alloy. The obtained surface roughness after finishing with MR fluid of Type – I is 10 nm and with MR fluid of Type – II is 70 nm. From wettability study, it is found that the surface finished with MR fluid of Type – I is hydrophilic in nature while with MR fluid of Type – II is hydrophobic. The surface characteristics obtained from MR fluid of Type – I is better suited for semi-permanent type of implants or implants which partake in relative motion like femoral part of knee joint and hip joint. From experimental studies, it is found that in MFAF process parallel toolpath performs better than spiral toolpath while finishing Ti alloy at the nanometer level. 3D surface roughness parameter (Sa (arithmetic mean of absolute height), Spk (reduced peak height), Sk (core roughness depth) and Svk (reduced valley depth)) values of the finished surface provide an understanding of the surface characteristics
Supervisor: Manas Das