Selective Laser Melting of Ti-6Al-4V Lattices: Case Study on a Spinal Cage Prosthesis

Abstract

Biomedical prostheses are artificial devices suitable for the replacement of missing or inefficient parts of the body, implanted to reduce the anatomical or functional deficiency, and sometimes also applied for aesthetic purposes. Despite this type of medical devices represents today a very innovative sector from the medical and engineering point of view, some issues, inherent to the interaction between human body and the external hosts must be considered. It is important that the weight and porosity of the prosthesis respect the patient’s physiological equilibrium which permit an appropriate osseointegration where needed. A typical solution is a lattice structure, which can be manufactured by Additive Manufacturing techniques which, as known, permit to build complex geometries in comparison with other processing routes. Lattice structure are typically characterized by both stiffness and strength significantly lower than the full part of the structure. Generally, for this reason, the lattices are applied to the low-stress areas, leaving a portion of solid sufficient to transmit the loads involved, or in such a way to guarantee the desired flexibility of the part-itself. During the design of lattices some limitations regarding their printability must be considered, such as the minimum printable dimension and the necessary support parts. A Design of Experiment analysis was conducted to identify the optimal parameters to manufacture a spinal cage with negligible porosity via laser powder bed fusion using Ti6Al4V alloy.