There are two different types of Ink Jet Printers: The Continuous Ink Jet Printers (CIJ) and Drop on Demand (DoD) Printers
What is Continuous Ink Jet Printing (CIJ)?
Ink is pressured by a ink supply pump and flow from the ink bottle to the nozzle. The nozzle uses ultrasonic vibration to break a pressurized ink stream into small droplets as it leaves the nozzle. The drops are ejected from the nozzle at high speed. They pass through the charge electrode tunnel / and then on between the deflection electrode.
Here the drops are deflected, by an amount which depends on the charge they were given by the charge electrode.
After the drops leave the region of the deflection electrode they continue to travel in their new direction until they pass out of the printhead and to the substrate.
Drops that aren't required for printing are caught by the gutter and subsequently recycled back to the ink bottle.
What is Drop on Demand (DoD)?
In the process of DoD the ink drops are only produced when they are needed for printing. The ink is stored in a small capillary tube. Because of underpressure in the capillary tube, the ink is protected from leakage. Only when an ink drop is requested, it will be activated and printed on the substrate.