Research on nozzle and needle combination for high frequency piezostack-driven dispenser

An on-off valve piezostack-driven dispenser is used as a study object to investigate the influence of the needle and nozzle combination on the high frequency jetting. Firstly, the jetting dispensing process and fluid dynamics are studied. Secondly, FLOW-3D software is used to model and simulate the needle and nozzle with different mating angles of sphere-sphere, sphere-short cone, sphere-short cone and cone-cone. The operating performances of different matching forms are compared and summarized according to the simulation results. Thirdly, the designed spherical-spherical needle and nozzle with 180° are grinded and installed on the dispenser, and the experiment system is built. By using a glycerol/alcohol mixture with a viscosity of 180 cP, we can realize the industrial frequency of 360 Hz in droplet continuous dispensing, and the average diameter of droplets is 525 μm. Moreover, the viscosity of 800 cP industrial epoxy resin form droplets have good geometry. under the conditions of nozzle diameter of 100 μm and square-wave frequency of 320 Hz, the variation of the droplet diameter is within ±2%. The findings in this paper can guide the design of nozzle and needle for jetting dispenser, which is used to meet specific industrial requirements.