Multi-Response Optimization of FDM Process Parameters for Enhanced Mechanical Performance and Reduced Weight of PLA and PLA-CF 3D-Printed Parts

This work investigates the influence of fused deposition modeling (FDM) parameters on the tensile properties and material consumption of FDM-printed samples. The study focused on extrusion-related parameters that directly govern material deposition during FDM printing, including extrusion temperature (ET), layer thickness (LT), and extrusion multiplier (EM). The combined effect of these parameters on the properties of FDM-printed parts has not been sufficiently investigated, particularly for polymer composites. Therefore, neat polylactic acid (PLA) and carbon fiber-reinforced PLA (PLA-CF) were considered. Standard tensile samples were used to evaluate the effect of ET, LT, and EM on the modulus of elasticity (E), yield strength (yield), ultimate tensile strength (UTS), and sample weight. Statistical analysis was conducted based on the response surface methodology (RSM). Desirability analysis was used as a multi-objective optimization method to maximize tensile properties and minimize material consumption. Fractographic analysis was performed using scanning electron microscopy. Statistical results showed that EM and ET significantly influenced E, yield strength, and UTS, with EM being the most influential factor, contributing 75.47–90.50% to the responses in both materials. EM had a greater influence on the tensile properties of neat PLA than PLA-CF, whereas ET showed the opposite trend, with a stronger influence on PLA-CF than on neat PLA. Increasing EM enhanced tensile performance by shifting the failure mechanism from highly raster-dominated/interfacial fracture occurring along the print boundaries at low EM (96%) to bulk-material-dominated fracture at higher EM (104%). The higher prevalence of pores and voids in PLA-CF resulted in lower yield strength and UTS than neat PLA, highlighting the need to optimize FDM parameters for composite materials. The optimal settings (230 °C ET, 0.15 mm LT, and 104% EM) simultaneously maximized E (PLA: 3.583 GPa; PLA-CF: 4.507 GPa), yield (PLA: 51.23 MPa; PLA-CF: 41.30 MPa), and UTS (PLA: 55.13 MPa; PLA-CF: 47.57 MPa) while minimizing specimen weight (PLA: 5.907 g; PLA-CF: 5.728 g). However, the sensitivity analysis provided additional insight by showing that a slight increase in EM from 104% to 106% further improved the tensile properties of PLA-CF, whereas 104% remained the optimal EM for neat PLA.