Response Surface Methodology (RSM)-Based Evaluation of the 3D-Printed Recycled-PETG Tensile Strength

In this research, an investigation related to the tensile testing of 3D-printed specimens, under different fabrication parameters, is presented. The control samples were fabricated using Recycled-PETG: EVO (NEEMA3D™, Athens, Greece). It consists of recycled polyethylene terephthalate glycol (PETG) raw material, already used in industry, modified so that it becomes filament and can be printed again. More specifically, the parameters set to be studied are the percentage of infill, the speed and the type of infill. Both infill density and printing speed have three value levels, whereas for the infill pattern, two types were selected. Two sets of 18 specimens each were fabricated, with respect to the different parameter combinations. Through the results of the tests, the maximum tension of each specimen was obtained separately. Of the three parameters defined, it was found that the most important are the type of infill (44.77%) and the percentage of infill (24.67%). Speed (13.22%) did not strongly affect the strength of the specimens. In conclusion, the empirical model developed was considered reliable in terms of the value of the squared error, R-sq(pred) (97.72%), but also of the rest of the resulting analysis residual graphs (through the full factorial design).