Effect of Printing Angle on Mechanical Properties of Fused Filament Fabrication (FFF)-Printed Polymers for Below-Knee Prosthetic Sockets: An Experimental and Finite Element Analysis Study

This study investigates the influence of printing angle on the mechanical performance of 3D-printed prosthetic sockets through an integrated experimental and computational approach. Tensile tests were conducted on Acrylonitrile Butadiene Styrene (ABS), Polylactic Acid (PLA), and enhanced PLA (PLA+) specimens fabricated at four orientations (0°, 30°, 60°, and 90°). The results confirmed clear printing orientation dependence, with Young’s modulus and ultimate tensile strength varying across printing angles in a material-specific manner. The experimentally determined Young’s modulus for each material–orientation combination was implemented as an equivalent isotropic elastic input in a separate finite element simulation of a patient-specific transtibial socket under simplified quasi-static stance loading. The FE simulations revealed that PLA+ printed at 0° provided a balanced structural response: it maintained von Mises stress within the socket at 1.98 MPa, limited displacement to 0.29 mm, and kept interface contact pressure at 0.089 MPa. In contrast, the more compliant ABS, particularly at a 90° orientation, exhibited a higher displacement of approximately 0.37 mm, which may influence socket compliance. This research provides quantitative, data-driven guidelines for the additive manufacturing of load-bearing medical devices, demonstrating that precise control of print orientation and material selection is essential for engineering prosthetic sockets that balance structural support with patient-specific interface requirements.