It might be tempting to use a laser or ink-jet printer to produce labels when you first start to need them, but they are not always the best for printing runs of barcode labels.  Thermal printers are still digital, but they are industrial machines, with fewer moving parts than other types of printer, and are highly reliable.  The labels they produce are more waterproof, and have a longer shelf life than many others.

 

They have the advantage of not needing to be connected to a PC (but they can be, if required), and  incorporate a high speed processor which means fast job processing and immediate label production.

 

A thermal printer uses a printhead that comprises 600 or more individually controlled elements side-by-side that heat up to transfer the ink from a heat-sensitive ribbon onto the label.  These print head elements are usually 1/8 or 1/12 of a mm in width, so they can print the different widths of the bars of a barcode very quickly and accurately.  They can also print text and images, if required, in the same colour, which for barcodes needs to be black.  The ribbon is the same width as the printhead and moves at the same speed as the labels being printed, and is used only once.

 

This technique is known as thermal transfer printing, and it produces high quality labels.  The wax-based ink is transferred by the heat of the printhead onto the label where it cools down and is permanently printed on the surface.  These labels have a shelf life of over a year, can cope with heat and sunshine, and are fine for use outside.  You can also choose from a wide range of materials to print on, such as foils and films as well as paper.

 

Direct thermal printing takes place when the same printer is used without a ribbon, but with heat-sensitive labels instead.  This paper is known as thermochromic, or thermal paper, and the coating turns black when it is heated to produce the image.  Even when they have cooled down, these labels remain heat and light sensitive, so they cannot be used to label, say, warm bread, or plant labels kept outside in bright sunshine.  They are very useful when you know the labels will not be getting warm or exposed to much daylight, for example on outer cases.  Although you save money by not having to buy ribbons, the printheads wear out more rapidly, and the print quality is not so good.

 

Thermal printers come with a fixed printhead width of nominally 2, 4, 6 or 8 inches, so you need to choose the right size printer for your job.  The 6 inch (162 mm) wide printheads are suitable for producing A5 sized logistics labels (pallet labels), while the 2 inch (54 mm) wide printers are fine for individual product barcode labels.