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) 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°-PO, 0.2 mm-LT, 20 mm/s-PS, 220 °C-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/m3 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.
•Optimization of tensile properties was achieved using the effect of multiple process parameters.•Tensile properties of the optimized PLA parts have been significantly improved.•Process parameters - tensile properties relationship was analyzed in detail.•ID, NOL and LT parameters highlight the maximum contribution to properties improvement.•The optimized properties of the FFF printed PLA parts are higher than those in the literature.
This paper presents a proposal to synthetize a thermoplastic polymer from glycerol designed to be used as feedstock for additive manufacturing (AM) based on the material extrusion (ME) principle. A ...first round of synthesis was carried out considering different variables to search a thermoplastic solid without stickiness. After the evaluation of some AM–ME basic requirements, two other synthesis groups (the second and third rounds) were prepared to verify a proper catalyst amount and reaction time. These trial samples were characterized by infrared spectrometry and thermogravimetric analysis. The material obtained which was considered the most suitable showed an amorphous structure and a glass transition slightly below room temperature. In the end, this polymer was used as feedstock to print basic geometric specimens and evaluate both filament and layer adhesion. The result suggests the feasibility to synthetize a thermoplastic polymer from glycerol for AM–ME technology. The polymer obtained from the renewable resource has the potential to become an option for this technology. However, further studies considering additives are required to improve the polymer properties, starting by increasing its glass transition temperature. In summary, the polymer obtained from the renewable resource has the potential to become an option for AM–ME technology.
