A Study of the Jetting Failure for Self-Detected Piezoelectric Inkjet Printheads

Piezoelectric (PZT) can be used as a sensor to measure the pressure changes in the flow passages after being utilized as an actuator in inkjet print-head. Monitoring the sensing signal from the PZT, one can distinguish a good jetting from malfunction of jetting including the failure of ejection. Because the surface of ink is vulnerably exposed to the air at the nozzle orifice, unstable jetting easily leads to form an air pocket at the nozzle exit, which causes to stop jetting drops any longer. As a result, the air bubble entrapped on the flow passage or any malfunction of jetting leads to changes in the residual oscillation of the PZT from that in the normal jetting condition. In this study, a scanning device for detecting bad performing nozzles for a print-head of 256 nozzles in a period of less then 0.5 s has been developed to check the jetting condition in intermittent printing period. The PZT sensing signal was measured right after the voltage waveform is applied to the print-head and compared to the reference sensing signal of the standard jetting condition.