Authors: H.M.A. Wijshoff
Affilation: Océ Technologies B.V., Netherlands
Pages: 448 - 451
Keywords: inkjet, drop formation, modelling
Drops are generated with a piezo inkjet device. A piezo actuator drives each channel. Drops are measured with stroboscopic illumination or high-speed camera recordings. The phenomena inside the channels are hard to measure. Modeling give the details on ink flow and acoustic pressure waves. The drop leaves the nozzle with a relative high speed. At tail break-off a secondary tail is formed. The small secondary tail breaks up in very small droplets, which are dragged along with an air-flow induced by the firing of drops. After break-off the tail-end tends to form a drop, which accelerates the tail end. The speed of the tail is not affected by the driving waveform, while the head of the drop is highly affected by the driving amplitude. Long tails break up into satellite droplets, the Rayleigh instability. At a very high drop speed, fast satellite drops are formed because of a supercritical accelration of the ink in the nozzle. Slow satellites are formed when the distribution of mass and momentum in the drop is not optimal. Understanding the drop formation process is the first step to realise a maximum jetting stability and to control and manipulate the drop formation.