Inkjet technology belongs to the group of non-impact printing (NIP), i.e. it belongs to the printing processes that work without a fixed printing form and without real pressure in the physical sense.
The basic principle of inkjet (=ink jet) printing is simple:
A print head uses a nozzle to transfer small ink droplets (dots) onto the surface to be printed. The printer controls (in most cases) two movements: the lateral movement of the print head and the vertical movement of the print medium.
Printing without printing
A special feature of IJ printing is the non-contact transfer of the ink to the material; this also enables printing on uneven, structured surfaces.
The two main procedures are BubbleJet (Thermal Inkjet) and Piezo inkjet. Both are used in large format systems with print widths of up to five meters as well as in small desktop inkjet printers. The basic principle of ink ejection is very similar for both methods. In front of the nozzle is a chamber that is filled with ink. By reducing the volume of this chamber, the droplet of ink is ejected through the nozzle. The difference lies in the technique used to achieve this reduction in volume.
Bubble Inkjet (Thermal)
The water-based ink is heated very quickly by the heating element in the print head to up to approx. 400°C. The resulting vapor bubble explosively throws drops of ink out of the nozzle onto the printing material.
The droplet size is physically specified and therefore not variable. Because of the heat, BubbleJet printheads will wear out faster and need to be replaced more often. The ink can only flow again when the element has cooled down enough for the vapor bubble to contract. This makes the process a little slower.
This technology can only be used for water-based inks.
Manufacturers: eg Canon and HP
Piezo inkjet
These printers make use of the property of piezoceramics to change under voltage to deform: An electrical impulse changes the shape of the piezo element.
This change in shape creates a pressure pulse in the ink channel, which causes a drop of ink to be ejected from the nozzle. The size of the ejected drop can be over control the electrical impulse very precisely (variable dot size).
Theoretically, piezo print heads are indestructible because they are not exposed to thermal stress. However, they have a higher purchase price.
Water-based, eco-solvent, real-solvent, UV-curing, latex and DyeSub ink systems can be used with this technology.
Manufacturers: eg Epson, Roland, Mutec and Brother
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