Continuous Ink Jet (CIJ) is a continuous drop process for inkjet printers. This process generates a continuous ink jet that is forced through a micrometer-fine nozzle at high pressure of more than 30 bar. To ensure that the ink jet experiences the highest possible outlet pressure, the print nozzle is shaped like a pyramid or cone at the rear. In addition, the ink must be able to flow, which is ensured by the addition of solvents, and the ink must be electrically conductive so that it can be deflected.
In the print head of CIJ printers, a piezo element provides pressure control and modulates the ink jet so that it emerges from the print nozzle as a continuous stream of microfine ink droplets and is sprayed toward the medium at high pressure or high velocity. The exit velocities at the high-pressure nozzle are between 10 m/s and 50 m/s. The number of ink drops is between 100,000 and 150,00 micro drops per second
In order for the ink droplets to be controlled, they pass through a pair of electrodes with an electric field located immediately behind the outlet nozzle, where they are electrically charged. The ink jet then passes through another pair of electrodes that electrostatically deflect the charged ink droplets.
The various CIJ processes
When charging the ink droplets, a distinction is made between two processes, which are ultimately reflected in the deflection of the ink jet. There is the binary deflecting process and the multi-deflecting process. In the binary process, the ink drops are electrically charged or not charged. The charged drops can be deflected by the deflection electrodes, while the non-charged drops fly directly onto the medium without directional influence. In the other process, Multi Deflecting, the ink drops are charged differently and are thus deflected differently. This allows the ink jet to be printed wider. In both processes, the excess ink is collected in a container and fed back into the circuit.
Piezo printers such as the CIJ printer work not with just one nozzle, but with an array of many nozzles. They have a resolution of 1,200 dpi and are ideal for printing on uneven surfaces, packaging materials, cans, bottles or cables.