Assessment of geometric variations in fused filament fabrication: impact of material and process setting

Abstract Additive Manufacturing enables the production of complex and customized structures but achieving consistent geometric fidelity and dimensional control remains challenging. Variations in form and feature orientation can compromise functional performance, making it essential to understand how process and material parameters affect geometric deviations and support robust qualification. This research investigates the effects of infill density, scale, and material type on geometric variations in Fused Filament Fabrication parts. Two shapes (prismatic and solid-of-revolution) were designed, with geometric variations grouped by feature orientation (vertical, horizontal, and inclined). The experimental plan considers three infill density levels (25%, 50%, 75%), three scale factors (1:1, 1.5:1, 2:1), and four materials (PET-G, PET-G CF, Nylon, Nylon CF), for a total of 120 samples, whose actual geometries were reconstructed via laser scanning, providing the basis for evaluations of data through numerical analysis. The results revealed that input parameters affect geometric accuracy, negatively impacting inclined features with increasing scale, while improving some horizontal features with increasing infill density. Materials, particularly carbon fiber reinforced, help reduce deviations, particularly in vertical geometric features. The study emphasizes the importance of selecting appropriate input variable settings and material types to achieve the desired accuracy, providing a tolerance catalogue within a specified range for designers and engineers to define tolerances for 3D-printed parts. Graphical abstract