Study on the Optimization of FDM Parameters for the Manufacture of Three-Point Bending Specimens from PETG and Recycled PETG in the Context of the Transition to the Circular Economy

This study presents the results of optimizing FDM 3D printing parameters (layer height deposited in one pass-L_h and filling density-I_d) to enhance the mechanical performance of three-point bending specimens made from PETG and recycled PETG (rPETG). The objectives of the study are to investigate the influence of variable parameters (L_h and I_d) on the three-point bending behavior of additively manufactured specimens by thermoplastic extrusion of PETG and rPETG. It is also aims to optimize the manufacturing parameters to maximize mechanical performance, but also to evaluate the potential of using rPETG in mechanical engineering applications. The materials analyzed in this study are PETG and recycled PETG (rPETG), in the context of promoting the concept of circular economy. Using the QIDI Q1 Pro 3D printer, and the variable parameters of FDM, L_h = (0.10; 0.15; 0.20) mm and I_d = (50; 75; 100)%, 90 three-point bending specimens (45 from PETG and 45 from rPETG) were additively manufactured. To determine the mechanical strength characteristics under three-point bending stress, all 90 additively manufactured specimens were tested in three-point bending using a Barrus White 20 kN universal testing machine. The maximum bending stress is influenced by the two considered variable parameters of FDM (L_h and I_d), the parameter with the greater impact being I_d. Comparing the results of the maximum bending stresses of the additively manufactured specimens made of PETG and rPETG using the optimal parameters, it was found that the maximum bending stresses are higher in the case of the rPETG specimens, which highlights the potential of using recycled plastics in mechanical engineering applications.