Additive Manufacturing Process Parameter Optimization for Titanium-Alloy Orthopedic Implants

Orthopedic implants are widely used for treating bone tumors and trauma defects in patients. The complex and organic geometry of patient-customized implants (PCIs) required in single order quantity makes them suitable for fabrication using additive manufacturing technologies such as Laser beam powder bed fusion. While there is considerable technical literature on these technologies, the choice of optimal process parameters to obtain the required quality considering the relevant applicable international quality standards for orthopedic implants is still a major challenge for the manufacturers. This experimental work relies on the minimum requirements of various mechanical properties recommended by ASTM F3001-14 and ASTM F136-13 standards for determining the optimal process parameters for PCI manufacture. Ti6Al4V ELI (Titanium–6Aluminum–4Vanadium Extra-Low-Interstitial) alloy test samples were fabricated using a Direct Metal Laser Sintering (DMLS) system. The three most critical printing parameters, namely, laser power, laser velocity and hatch distance, were varied in three levels using the Taguchi approach. Properties such as ultimate tensile strength, percentage elongation and part density were considered for optimizing the process parameter combinations using VIKOR, a multi-criteria decision-making technique. The results show that a combination of moderate laser power, high laser velocity and low hatch distance values produce implants with superior mechanical properties. The proposed methodology and results are expected to help researchers and manufacturers in choosing the initial process parameters for PCI fabrication.