Effects of Drag Finishing on a SLM-Manufactured Titanium Reconstruction Plate

Abstract

The medical field is one of the many areas which constantly benefits from the advantages of additive manufacturing (AM), due to the possibility of fabricating custom implants with complex shapes. The purpose of this paper was to investigate the effect of drag finishing on the surface roughness of mandibular reconstruction plate made from pure titanium (Ti) and fabricated by the selective laser melting (SLM) process. The surface roughness parameters considered were Ra, Rq, Rt, Rz, Sa, Sq, and Sp. The measurements were done on side surfaces and top ones. Using computed tomography (CT) scan, we also analysed the micro-porosity and the factors leading to differential porosity. In general, the Ra surface roughness suitable for maxillofacial implants is between 0.2 μm to 2 μm. The present work shows that the as-build part has the Ra roughness on the outer boundary around 9.1 μm (10.7 μm Sa) and 24.4 μm on the top surface (32.4 Sa). After we adopted the drag finishing parameters, we reduced the Ra surface roughness to 1.6 μm on the outer boundary (3.1 μm Sa) and 11.4 μm on the top surface (26.8 Sa). Due to printing conditions, the CT investigation indicates that the extremities of the reconstruction plate and the middle segment have different micro-porosity levels. This aspect can influence the mechanical properties and a physical test was required. To determine the mechanical resistance of the actual implant, we used the Inova testing system. Under continuous tensile load, the fracture appears nearby the screw hole at 402N and 3.3 mm displacement. The voids identified by CT have a limited influence on the fracture area. To limit the micro-voids volume and distribution, future studies are needed to analyse the impact of SLM technological conditions on micro-porosity.