Optimal shape design of printing nozzles for extrusion-based additive manufacturing

The optimal design seeks the best possible solution(s) for a mechanicalstructure, device, or system, satisfying a series of requirements and leadingto the best performance. In this work, optimized nozzle shapes have beendesigned for a wide range of polymer melts to be used in extrusion-basedadditive manufacturing, which aims to minimize pressure drop and allow greaterflow control at large extrusion velocities. This is achieved with a twofoldapproach, combining a global optimization algorithm with computational fluiddynamics for optimizing a contraction geometry for viscoelastic fluids andvalidating these geometries experimentally. In the optimization process,variable coordinates for the nozzle's contraction section are defined, theobjective function is selected, and the optimization algorithm is guided withinmanufacturing constraints. Comparisons of flow-type and streamline plots revealthat the nozzle shape significantly influences flow patterns. Depending on therheological properties, the optimized solution either promotes shear orextensional flow, enhancing the material flow rate. Finally, experimentalvalidation of the nozzle performance assessed the actual printing flow, theextrusion force and the overall print control. It is shown that optimizing thenozzle can significantly reduce backflow-related pressure drop, positivelyimpacting total pressure drop (up to 41%) and reducing backflow effects. Thiswork has real-world implications for the additive manufacturing industry,offering opportunities for increased printing speeds, enhanced productivity,and improved printing quality and reliability. Our research contributes toadvancing extrusion-based printing processes technology, addressing industrydemands and enhancing the field of additive manufacturing.