Under the pressure of the ink supply pump, ink flows from the ink tank through the ink path, where pressure and viscosity are adjusted before entering the spray gun. As the pressure continues, the ink is ejected from the nozzle. When the ink passes through the nozzle, it is broken apart by a piezoelectric crystal into a series of continuous, equally spaced, and uniformly sized ink droplets. The ejected ink stream continues to move downward and passes through a charging electrode, where the droplets are charged.
A certain voltage is applied to the charging electrode. When the droplets separate from the conductive ink stream, they instantaneously acquire a negative charge proportional to the voltage applied by the charging electrode. By varying the frequency of the charging electrode's voltage to match the frequency at which the droplets break apart, each droplet can be given a predetermined negative charge. With continuous pressure, the ink stream continues to move downward and passes between two deflection plates, each carrying positive and negative voltages. Charged droplets will be deflected as they pass through the deflection plates, with the degree of deflection depending on the amount of charge carried. Uncharged droplets do not deflect and continue to fly downward into the recovery pipe, ultimately returning to the ink tank for recycling.
The charged and deflected droplets fall onto the object passing in front of the vertical nozzle at a certain speed and angle.