Parameter Optimization for Printing Ti6Al4V-Alloy Patient-Customized Orthopaedic Implants by Laser Powder Bed Fusion Using Physio-mechanical Properties and Biological Evaluations.

Abstract

A class of additive manufacturing technologies called Laser powder bed fusion (LPBF), which allows fabricating metallic components with complex geometries in near-net-shape, can be employed for fabricating patient-customized orthopaedic implants. Selection and optimization of the LPBF process parameters are critical to achieving the required biomechanical properties and fabricability of such implants. The process parameters of direct metal laser sintering, the most widely used LPBF process, were optimized for fabricating Ti6Al4V ELI orthopaedic implants, based on ASTM and ASM standards. The parameters included Laser power, Laser velocity and hatch distance, which were varied using Taguchi approach. A multi-criteria decision-making technique (TOPSIS) was employed to optimize the process parameters considering yield and ultimate tensile strength, percentage elongation, part density, volumetric energy density and printing time. In-vitro cytotoxicity and in-vivo muscle implantation were performed on the optimized samples for determining the suitability of the parameters for biomedical applications. A combination of medium laser power, higher laser velocity, and lower hatch distance with values 200W, 2200mm/s and 0.08mm, respectively, was found to be suitable for producing implants. Based on the type of LPBF technology in use, an implant manufacturer can select the initial set of parameters using a similar approach and improve them further based on experimental results. The optimized parameters were found to be suitable for developing orthopaedic implants, in terms of physical, mechanical and biological criteria. The methods and results presented in work are expected to assist the implant manufacturers in meeting the expected user requirements and quality standards.