Thermal printing

Thermal printer for labelling

For product labelling, a thermal printer must have certain specific capabilities. A precise print with sharp outlines is essential to get machine-readable results. Best results can be achieved with direct-thermal and thermal-transfer printers.

• Direct thermal: This type of thermal printer needs special thermal paper, which reacts with the heated printhead. Where the printhead touches the paper, it turns black. The modern thermal paper is much more resistant to environmental influences than before so that the colour stays fresh for several years.
• Thermal transfer: This system uses colour foil, or thermal-transfer-foil, to get the print on the paper. The printhead is equipped with hundreds of tiny heating elements that can be computer-control activated. The foil runs between the printhead and paper and is melted by the printhead where the heating elements are activated. The plain surface of the foil achieves a fine and sharp print with a slight shine. The advantage of the thermal-transfer system is the longer shelf life of its prints compared to the direct-thermal prints.

Weber-marking.com offers direct-thermal as well as thermal-transfer printers. Some of the thermal printers, like the Legi-Air 4000, run with both systems.

Thermal printer with inkjet systems

Thermal printers that have to print directly on the product packaging often use inkjet systems. The main advantage is that these systems are able to print on various surfaces like paper, cardboard packaging, synthetic materials or metal. It is especially used for pharmaceutical, cosmetic and food packaging and in the postal service. Thermal inkjet printers use ink cartridges with lots of tiny chambers that can be heated by an electric impulse.

The heat provokes the building of a small vapour bubble which pushes the ink through the nozzle. The tension of the vapour bubble, as well as the surface tension of the ink drop, cause the ink to hurl back within a fraction of a second. Precise and high quality prints of text, barcodes and graphics can be achieved. Another system of thermal printers with inkjet technology is the piezoelectric inkjet printer, or piezo-printer.

With this principle, the walls of the ink chamber are heated by an electrical pulse, so that they extend through the heat. The ink is pressed out of the nozzle and onto the object. By stopping the electric impulse, the walls return to their original position. In the chamber a vacuum is created, pulling the rest of the ink that has not been used for the print back into the cartridge. Both systems of thermal printers are offered on weber-marking.com.