Effect of Multiple Process Parameters on Optimizing Tensile Properties for Material Extrusion-Based Additive Manufacturing

Additive manufacturing technology, and especially the material extrusion (MEX) process, is far from the maturity level and, due to the contradictory data reported in literature, it requires a deeper understanding of the mechanical behavior of 3D printed components. The paper investigates the influence of seven different process parameters on the tensile behavior of printed dog-bone specimens through MEX process. Parameters such as infill pattern-IP (grid, honeycomb and triangular), infill density-ID (40%, 70% and 100%), printing orientation-PO (0, 45 and 90), layer thickness-LT (0.1, 0.15 and 0.2 mm), printing speed-PS (20, 40 and 60 mm/s), nozzle temperature-NT (200, 210 and 220 C-degrees) and number of outer layers-NOL (1, 2 and 3) are investigated on Polylactic acid (PLA) thermoplastic material. The optimal levels of the investigated process parameters are TR-IP, 100%-ID, 0(degrees)-PO, 0.2 mm-LT, 20 mm/s-PS, 220 C-degrees-NT and 3-NOL. The optimized specimens lead to a maximum tensile strength value of 62.42 MPa, a fracture energy of 1.46 MJ/m(3) and a very good dimensional accuracy. However, the maximum contribution to the percentage increase in tensile strength is found in the ID (43.41%), NOL (25.73%) and LT (20.58%) process parameters, and the minimum in the IP (0.99%), PO (4.48%) and PS (5.16%) parameters. Furthermore, the tensile strength values of the optimized specimens are higher than most literature reports on MEX-printed and injection-molded PLA parts.