Pressure response and droplet ejection of a piezoelectric inkjet printhead

The present study aims to investigate the pressure rise in the ink flow channel and the ink droplet formation process of a piezoelectric printhead after an electrical pulse is applied to the printhead. The ink flow channel is modeled as a straight circular pipe followed by a convergent nozzle, Both numerical analysis and experimental observations are performed in this study. In the numerical analysis, a characteristic method is used to solve the one-dimensional wave equation to obtain the transient pressure and velocity variations in the flow channel of the printhead. In this analysis, the channel is assumed to have a non-uniform cross section. In addition, a flow visualization system was set up to observe the ink droplet injection process. After the piezoelectric material is driven by the input electric pulse, the ink droplet images are immediately captured by a charge-couple device (CCD) camera converted to a digital image via a frame grabber, and stored in a computer. The results obtained from the experimental observations are also compared with the numerical prediction. The effects of electric pulse shape and voltage on the ink injection length and the ejected droplet weight are also presented. (C) 1998 Elsevier Science Ltd. All rights reserved.