3D-printed motorcycle seats: Replicating polymer foam performance for rapid prototyping and rider comfort

The development of prototypes prior to the market launch of final products requires adapting production components to reduce costs and increase flexibility for potential modifications. While the manufacturing of rigid or structural components is well-established and widely practiced, the production of expanded materials presents significantly greater challenges due to the final product's reliance on the specific process employed. Changing the process to lower costs necessitates reproducing the same mechanical behaviour and appearance to ensure validation in terms of both style and function. This study focuses on replicating the behaviour of expanded polyurethane foam, commonly used in motorcycle seat padding, using thermoplastic polyurethane (TPU). The aim is to create a prototype or a customised version of the foam. The internal stochastic closed-cell structure is designed using slicing software, and test specimens are subsequently fabricated through Material Extrusion (MEX) additive manufacturing and subjected to compression testing. The results emphasise the critical influence of material hardness and infill density on the force-displacement curves. An experimental map, derived from three parameters (material hardness, elastic modulus, and foam density) illustrates the behaviour of the specimens, with iso-lines representing constant density. This map serves as a valuable tool for accurately replicating desired foam properties, providing guidance on material selection based on force-displacement characteristics.