Transient Phenomena During Drop Formation In DOD Printing

Abstract

Given the rapid evolution of ink jet technology and the ever-increasing demand for enhanced resolution, excellent printer performances under different industrial operating conditions are deemed necessary. The performance of an ink jet printer depends not only on the head assembly, but also on the coupling between the ink rheological behavior and the waveform signal applied to produce the droplet. In order to better follow and understand the phenomenon of filament pinch-off we have developed different techniques which are detailed here.In this paper, we will first focus on the dynamics of filament break-up. The development of finite time singularities i.e. the evolution versus time of quantities such as the minimum radius of the filament is given. It is also shown here that the thinning of the neck during droplet snap off displays behaviors which are quite different depending on the inks used. These new results complement some of our earlier measurements of the drop formation phenomenon.The other results reported in the paper concern the transient contraction of the filament being swallowed in the drop following break-off. This is the first time that such short lived filaments are captured and examined in detail. These results shed more light on the interaction between the fluid and the flow particularly when different waveform signals are used.Finally, we show that the framework of dynamic singularities which can be used to construct similarity solutions for hydrodynamic problems can prove to be helpful in the analysis of the pinch-off phenomenon in DOD ink-jet printing. Indeed, they allow to better quantify under the form of scaling laws the various nonlinear hydrodynamic phenomena from drop snap off to filament retraction and give a unified picture of the drop formation phenomenon.