Print Technology There are basically two different inkjet printing processes: Continuous inkjet technology is mainly used for industrial inkjet printing. In this process ink comes out of the nozzle continuously. The drops that hit the paper form characters and images, while the drops of ink that are not needed are diverted back to the ink reservoir.

Nowadays the drop-on-demand process is more widespread. This is the technology used in desktop printers and large-format inkjet plotters. A distinction is made between thermal inkjet (also known as bubble jet) and piezo inkjet.

1. Thermal inkjet
In thermal inkjet print heads the ink is heated electrically to such a high temperature that it expands and is ejected onto the paper through nozzles in the form of drops. The negative pressure produced by the ejection of drops ensures a continuous flow of new ink. One advantage of thermal print heads is their low cost. Their useful life is so short, however, that they have to be replaced every time the ink is changed.

2. Piezo inkjet
In piezo technology expansion or contraction is produced by changing the voltage applied to piezo crystals. This generates positive or negative pressure, causing drops of ink to be expelled or new ink to be supplied.
Piezo print heads offer very regular drop formation and last a long time. They are also substantially more expensive than thermal print heads, however.