Design and Experimental Validation of a Novel Ultrasonically Driven Coaxial Curved Hopper Nozzle for Additive Manufacturing

Abstract

Vibratory-assisted powder feeding technology facilitates precise, point-to-point powder delivery, which is crucial in additive manufacturing (AM). Previous research has frequently underestimated the pivotal role of the hopper in regulating powder flow, often resulting in unstable powder delivery within these systems. This study introduces a novel ultrasonic coaxial powder nozzle that incorporates a curved hopper and evaluates its functional efficacy. The ultrasonic driving unit of the coaxial curved nozzle was designed utilizing an equivalent circuit method, and its performance parameters were empirically assessed. Comparative analyses of curved versus conical hoppers were conducted, focusing on outflow characteristics of the curved hopper, which include exit velocities, trajectories, stress distributions, and porosity of the powder particles. The findings reveal that the constant contraction ratio of the curved hopper significantly mitigates the impact of particle stresses on dispensing velocity. Furthermore, the study investigated the effects of varying particle sizes and ultrasonic power levels on powder flow rates, establishing that stable powder flow is achieved when the ratio of outlet diameter to particle diameter ranges from 3.8 to 9.3, with minimal dependence on power variations. Long-term dispensing experiments confirmed that the ultrasonically driven nozzle maintained consistent and stable powder dispensing for periods exceeding 5 min, across particle sizes ranging from 80 to 200 mesh and at an ultrasonic power setting of 130 W. This research enhances the understanding of powder dynamics within the nozzle, advancing powder delivery methodologies for acoustic-assisted AM.