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For all the times that home computer printers jam, run out of ink, require resetting, and just generally fail to deliver a printed page when asked, it’s a wonder that high-usage commercial printers work so reliably. The tiny printer in a gas pump, for example, almost never fails to spit out the perfectly printed receipt for a purchase. Cash registers and credit card authorization machines, likewise, seem to work reliably and well all the time. After all if one of these machines stops working, it can shut down a small business or if they have more than one credit card machine, it can certainly reduce their throughput capacity. How do these machines work so much better than the printers we all have at home?

One of the reasons is that they are asked to perform a less complicated task. Home printers are required to print in multiple colors while most of the commercial point of Sale (POS) printers need only a single color. Home printers not only need to be able to print with a number of different colors, but each color must line up precisely with the others such that they can be blended to make a wide range of colors or portray an image that fades from one color into another without jagged edges marking imperfections in the alignments between the print heads for each color.

Even more fundamental however is the manner in which the POS printers are designed. For the most part, they are thermal printers rather than ink-based printers like those that are used at home. The lack of need for color printing allows the thermal printing process to be used. In thermal printing, the printer itself needs no ink at all, no ink cartridges, no multiple print heads, and no complications. Instead these POS printers use a special thermal paper that actually has the ink already embedded in the paper. When heat is applied to the paper by the thermal printer, the ink is released from the paper’s structure and it becomes visible as a printed character. Instead of applying ink to the paper, the thermal printer applies heat in the specific locations where printing should appear.

Not only does this eliminate the need to keep the printer stocked with ink all day long, but it actually allows the printer to be designed using a more simple design and far fewer moving parts. Fewer parts mean fewer things to wear out or to break down. The simple design of thermal printers, therefore, means they are much more mechanically reliable than ink-based printers. The use of thermal paper rolls instead of individual sheets of paper also prevents jamming and simplifies the mechanism.