Optimization of FFF parameters for enhanced tensile and shear strength of PLA + parts and mechanical performance of porous scaffolds

Fused filament fabrication (FFF) is widely used to produce polymer-based parts, particularly bioscaffolds, though mechanical performance depends heavily on process parameters. In the present study, a Taguchi L9 orthogonal design is used to examine the influence of printing angle, infill percentage, and layer thickness on tensile strength and torsion-induced shear stress of PLA + parts. Experimental results demonstrated that the printing angle exerts the strongest influence on both mechanical responses; specifically, increasing the angle from 0 to 90° caused a substantial decline in both tensile and shear strength. SEM analysis of the broken surfaces further confirmed the underlying failure mechanisms. Samples printed at 0° exhibited ductile tearing and strong interlayer bonding, while 90° samples failed in a brittle manner along weak interlayer boundaries. ANOVA results revealed that the printing angle accounts for 89.28% of the variation in tensile strength and 62.66% in shear stress, while the infill percentage emerges as a more critical factor for shear strength. The optimal process parameters, consisting of a 0° printing angle, approximately 60% infill density, and a layer thickness of 0.1 mm, yielded maximum tensile strength of 48.02 MPa and shear strength of 30.67 MPa. Following this optimization, porous scaffolds with 0–90° and 0–45° internal architectures were fabricated using these parameters and evaluated under compression. Experimental results revealed that the scaffold with a 0–90° arrangement possessed a compressive load-bearing capacity more than three times greater than that of the 0–45° scaffold.