PROGRESS IN ADDITIVE MANUFACTURING, 2025 (ESCI, Scopus)
The selection of an appropriate infill pattern in Fused Filament Fabrication (FFF) plays a critical role in determining both mechanical performance and production efficiency, as it directly influences interlayer adhesion. While various infill patterns have been extensively explored in the literature, this study introduces a novel configuration, referred to as Random Lines, and evaluates its mechanical behavior under torsional loading. The performance of Random Lines is compared against conventional infill patterns-including Lines, Grid, Gyroid, and Archimedean Chord-under identical manufacturing conditions. Standard infill geometries were generated using the open-source slicer Cura, whereas Random Lines and Archimedean Chord patterns were implemented via custom Python scripts. All specimens were fabricated using polylactic acid (PLA), and their mechanical properties were assessed according to the ASTM E143 standard for shear modulus. Given the complex interlayer bonding structures, the polar moment of inertia was determined numerically through image processing to enable accurate conversion of torque and twist angle data into shear stress and strain. The Random Lines pattern demonstrated superior mechanical performance, yielding a shear modulus of 880 MPa-39.1% higher than that of Archimedean Chord-and a yield strength of 26.3 MPa, marking an 85.7% increase. These enhancements, however, were accompanied by a reduction in toughness. Additionally, both Random Lines and Archimedean Chord exhibited smoother toolpaths with fewer retractions and discontinuities, resulting in shorter manufacturing times.