piezoelectric printer
Piezo printers are inkjet printers that use a piezojet. There are two processes: The drop-on-demand process and the continuous drop process, or continuous ink jet( CIJ). Both processes are pressure-controlled processes that exploit the piezoelectric effect. The piezoelectric effect means that by bending certain crystals, voltage can be generated, or conversely, by applying a voltage, a piezo crystal can be bent.
This piezo effect is exploited in piezo printers by using a piezo element to drive an ink jet through a nozzle. In the drop-on-demand process, the piezo element briefly deforms the print nozzle, creating a high pressure on the printing ink that causes an ink droplet to be ejected from the print head at high speed and sprayed onto the paper. The ink droplets have a velocity of between 10 m/s and 40 m/s. To prevent the ink from escaping further from the nozzle, the polarity of the voltage at the piezo element is reversed. The polarity reversal causes the piezo element to deform in the other direction, drawing the ink from the reservoir into the nozzle area.
In contrast to the drop-on-demand process, the Continuous Ink Jet Printer (CIJ) injects the ink jet quasi-continuously onto the paper at high speed. The pulse rate is much higher, producing approximately 100,000 to 150,000 ink drops per second.
With the piezo process, the droplet size can be controlled by pulses of different strengths and very small amounts of ink can be selectively sprayed onto the paper. These are currently in the range of a few picoliters (pl), or trillionths of a liter. The drop speed is higher than that of the bubblejet and is around 20,000 to 30,000 drops per second. Resolutions of 1,500 dpi can be achieved with the piezo process. These values are now exceeded many times over and are in excess of 5,000 dpi.