Jetting, In-Nozzle Meniscus Motion and Nozzle-Plate Flooding in an Industrial Drop-on-Demand Print Head
The state of the ink film at and near the nozzles of a drop-ondemand(DoD) print head during jetting has a direct impact on printing performance and reliability. We have developed highspeed imaging apparatus and analytical techniques to investigate the ink film dynamics on an industrial print head nozzle-plate in real-time. In addition to a direct correlation between the jet emergence velocity and drive voltage, drive-dependent variations in the oscillation of the ink meniscus in adjacent nozzles were also observed. Using a ray-tracing model to analyze the meniscus shape, the meniscus oscillations for both printing and nonprinting nozzles were found to be complex and involve elements such as pre-oscillation and high-order surface waves. The flooding of non-firing nozzles, deliberately caused by the application of maximum drive voltage to a neighboring nozzle, has been recorded and analyzed dynamically. The build-up of fluid in an annulus around the nozzle (flooding rate) has been characterized and compared with models for the net ink flow through the nozzle.