Track: Manufacturing

Abstract

Triply periodic minimal surface (TPMS) lattice structures have been identified as the most promising design structure for biomedical implants due to their controllable mechanical properties and porous architecture. Selective laser melting (SLM) is a state-of-art additive manufacturing (AM) technology that has enabled the manufacturing of complex geometries with customized designs. In this research work, two types of TPMS lattice structures viz. Gyroid and Diamond were designed and manufactured by the SLM process using SS316L material. This study evaluates the surface roughness, and dimensional accuracy of SLM-printed parts of SS316L TPMS lattice structures (Schoen gyroids and Schwartz diamond). The dimensional accuracy of as-built parts was investigated by performing a density test. A laser scanner was used to scan the SLM-printed gyroid and diamond lattice structure samples in order to study the deviations from the original CAD model. Surface roughness is measured at three different locations: the inner surface, the top surface, and the side surface. It was found that the average values of the Ra are 14.2µm, 13.1 µm, and ­­12 µm at respective surfaces for gyroid lattice structure and 13.4 µm, 12.5 µm, and ­­12.2 µm for diamond lattice structure. It was found that the inner surface roughness values of both the lattice structures fall in the range of 10 to 20 µm. This range was suggested by the literature for better bone-tissue interaction. From the experimentation, it was also found that the surface roughness of the gyroid lattice structure is comparatively higher than the diamond lattice structure. The lattice structure’s density was found at 7.62  g/cc for gyroid and 7.66 g/cc for diamond lattice structure, while the relative density of diamond structures was found to be 98.46% and 98.20% for gyroid structure. Finally, through this experimentation it was found that the SLM-built diamond lattice structure shows high accuracy compared to the gyroid lattice structure.