UV inkjet printer breaks down color liquid ink into fine particles through a nozzle. Some inkjet printers have three or four print heads for printing yellow, magenta, and black while others share a nozzle to achieve four-color printing.
There are two main technologies for UV inkjet printer: continuous inkjet technology and random inkjet technology. Early inkjet printers and current large-format inkjet printers used continuous inkjet technology, and the current popular inkjet printers generally use random inkjet technology. The continuous inkjet technology is represented by a charge modulation type, and the ink in the random inkjet system is jetted only when printing is required, so it is also called an on-demand type.
Continuous inkjet technology is represented by a charge modulation type. This inkjet printing principle uses a piezoelectric driving device to apply a fixed pressure to the ink in the head to continuously eject it. For recording, the vibration signal of the oscillator is used to excite the jet to generate ink droplets, and the droplet size and spacing are controlled. The print information from the character generator and the analog modulator controls the charge on the control telegram to form charged and uncharged ink droplets, and the deflection electrode changes the flight direction of the ink droplets, so that the ink droplets that need to be printed can fly to the paper and generate character or graphic records. Ink drops that do not participate in the record are recovered by the catheter. For the deflection electrode, some systems use two pairs of mutually perpendicular deflection electrodes to perform a two-dimensional deflection type on the ink droplet printing position while some systems use multi-dimensional control of the deflection electrode, that is, a multi-dimensional deflection type.
This continuous cycle inkjet system of UV inkjet printer can generate high-speed ink droplets, so the printing speed is high and plain paper can be used. Different print media can achieve high-quality print results and easy color printing. However, the structure of such a UV inkjet printer is more complicated than that of a random type: a pressurizing device is required for the ink, and the recycling device is required to recover the non-recording. A continuous UV inkjet printer is not efficient or accurate enough therefore can rarely be seen nowadays.
Random inkjet system, however, compared with the continuous type, is simpler, the cost of which is lower, and the reliability higher. the ink is ejected only when it is needed for printing, so it is also called on-demand. However, the ink droplet ejection speed is low due to the influence of the jet inertia. In this random inkjet system, in order to compensate for this shortcoming, many random inkjet printers employ a multi-nozzle method to increase the printing speed. Random inkjet technology mainly has two categories: micro piezoelectric and thermal bubble.
The micro piezoelectric system is provided with a transducer on a nozzle equipped with ink, and the transducer is controlled by a printing signal to control the ejection of ink.
Thermal bubble inkjet printers generally use thermal bubble inkjet technology to inject ink into the printing paper to form ink dots by heating, expanding and compressing ink in a short time, increasing the stability of ink droplet color and achieving high speed and high quality. Whether UV inkjet printer uses the heating or vibrating to produce ink drops, the result is the same, that is, attach tiny dots of ink on the paper. The smaller the ink dot, the higher the resolution of the printed image and the better the color effect.