Development of an Ergonomic Additively Manufactured Modular Saddle for Rehabilitation Cycling

This work reports the design, fabrication, and validation of a modular ergonomic saddle forrehabilitation cycling, developed through a combined additive manufacturing approach.The saddle consists of a metallic support produced by Laser Powder Bed Fusion (LPBF) inAISI 316L stainless steel and a polymeric ergonomic covering fabricated via Selective LaserSintering (SLS) using thermoplastic polyurethane (TPU). A preliminary material screeningbetween TPU and polypropylene (PP) was conducted, with TPU selected for its superiorelastic response, energy dissipation, and more favourable SLS processability, as confirmedby thermal analyses. A series of gyroid lattice configurations with varying cell sizesand wall thicknesses were designed and mechanically tested. Cyclic testing under bothstress- and displacement-controlled conditions demonstrated that the configuration with8 mm cell size and 0.3 mm wall thickness provided the best balance between complianceand stability, showing minimal permanent deformation after 10,000 cycles and stableforce response under repeated displacements. Finite Element Method (FEM) simulations,parameterized using experimentally derived elastic and density data, correlated well withthe mechanical results, correlated with the mechanical results, supporting comparativestiffness evaluation. Moreover, a cost model focused on the customizable TPU componentconfirmed the economic viability of the modular approach, where the metallic base remainsa reusable standard. Finally, the modular saddle was fabricated and successfully mountedon a cycle ergometer, demonstrating functional feasibility.