Analysis Of Piezo Inkjet Printing

There are three sub-processes during the droplet formation in the inkjet printing system,including jet formation process, pinch-off process, and droplet movement process. In thespecial case of inkjet system, the three processes were controlled by driving pulse and theproperty of ink..The driving pulse contains pulse time, pulse voltage and waveform of pulse. The effectof driving pulse in the droplet formation was investigated by numerical simulation. Theinfluence of sub-parts of pulse time on pressure wave at nozzle was studied, then theinfluence of pressure wave on droplet formation was studied. The paper has followingconclusion after the simulation. The pulse rise time trwill result in negative pressure at thenozzle, which will influence the resorption in the early time of droplet formation. The volumeof droplet jetted will increase when the pulse rise time is smaller. The pulse dwell time tdhasa limitation for the channel is fixed. The simulation results show that the final volume andspeed of droplet will increase with the dwell time, and then they will decline. The pulse falltime tfmainly influences the pinch-off process. When the fall time increases, the pinch-offtime will be longer and the speed and volume of droplet will relatively increase.The low viscosity ink has been widely used in inkjet printing industry and emergingelectric printing field. The paper designed the experiment to study the property of viscosity oflow viscosity ink and the driving pulse on the formation of droplet. The following result wasgot by the experiment. The viscosity of the fluid is lower, the smaller the damping force offluid. In the condition of low viscosity, the higher driving voltage will make the jet longer,which will produce satellite droplet easily. The droplet size and velocity increases withincreasing trand tf, while the tdincreases the variation in droplet size and velocity is declinedafter the first upward trend. Then, the paper studied the effect of waveform on the dropletformation. The result shows that when the two pulse waveform was used, the negativepressure produced by the second pulse will increase the power of resorption. By doing so, thelength of jet will be reduced and the system can produce single droplet.Finally, according to the practical application, the paper studied the influence of pulsevoltage on the droplet inkjet process by suing silver nitrate solution. The experimental resultsshow the value of pulse voltage has an interval. When the driving voltage exceeds the lowestlimit, the drop kinetic energy is not enough resulting in the droplet cannot be jetted. When thevoltage exceeds the upper limit, the kinetic energy will be too high to produce satellitedroplet for the speed of satellite will smaller than main droplet.