Acoustical and optical characterization of air entrapment in piezo-driven inkjet printheads
Detlef Lohse, Jos de Jong, Roger J.M. Jeurissen, Michel Versluis, Hans Reinten, Marc van den Berg, Herman M. A. Wijshoff · The Journal of the Acoustical Society of America · 2006
Stability of inkjet printers is a major requirement for high-quality printing. However, in piezo-driven inkjet printheads air entrapment can lead to malfunctioning of the jet formation. A voltage pulse applied to a piezoelectric element causes an ink-filled channel to deform, thereby creating a pressure waveform in the ink. Fluid acoustics are involved to guide the waveform energy towards the nozzle and to create pressure and velocity profiles needed for the droplet jetting process. Droplets are jetted every 50 μs, and the typical nozzle size is 30 μm. The piezo actuator is employed to actively monitor the channel acoustics and to identify distortions at an early stage. Modifications of the response of the piezo actuator indicate entrapped air bubbles and these allow us to investigate them. When the signal is employed as a trigger for high-speed imaging, the consequences of the entrained bubbles on the droplet formation can be visualized. [This study has been financed by the Fundamenteel Onderzoek der Materie (FOM) of The Netherlands under Grant. No. 02MFS39 and by Océ Technologies B.V.]