Surface Enhancement of Additively Manufactured Bone Plate Through Hybrid-Electrochemical Magnetorheological Finishing Process.

Abstract

Additive manufacturing or 3D printing provides the benefits of individualizing the implant per patient requirements. However, the poor surface quality of additively manufactured biomaterial is a major limitation. Hence, hybrid-electrochemical magnetorheological (H-ECMR) polishing is developed to improve the surface quality of fabricated parts. H-ECMR finishing is an advanced surface polishing operation that avails the synergic action of mechanical abrasion and the electrochemical reaction to enhance the surface quality of the workpiece without hampering its surface topography. Furthermore, the developed H-ECMR finishing process reduces the finishing time and produces a uniform surface quality compared with the conventional magnetorheological (MR) finishing process. However, the surface finishing of the parts having a hole-of-pocket feature through the H-ECMR finishing process is a major challenge as MR fluid gets trapped inside those holes or pockets. A feature-based hybrid H-ECMR finishing process is developed to resolve the issue. In this case, paraffin wax is applied to the holes and pockets before the H-ECMR process occurs. In the present work, bone plates are fabricated through selective laser melting, and their surface quality is further enhanced through the H-ECMR finishing process. Bone plates are necessary to provide mechanical stability during bone fracture healing by adapting to the chemical environment. The final R_a value of 21.37 nm is attained from 9.36 μm through H-ECMR finishing. Pin-on-disk study is carried out on the biomaterial to analyze its wear resistance. The surface topography of the workpiece is analyzed through scanning electron microscopy before and after finishing, and it was observed that a uniform surface is achieved after polishing. Apart from the average surface roughness (R_a ), other roughness parameters such as skewness (R _sk) and kurtosis (R _ku) are analyzed to study the attribute of the surface irregularities.