Dot Matrix Printing - What is dot matrix printing?
A method of printing; this process creates an image by striking a set of pins against a ribbon to transfer ink to the substrate in the form of small dots, which recreate the image being printed as a dot matrix pattern.
Dot matrix printing is one of the most common and popular examples of impact printing, and this printing process is based on the manual typewriter. Dot matrix printers have a printhead that contains a series of metal rods, known as “wires” or “pins”, an ink soaked ribbon, and a small guide plate to guide the pins to the substrate. Early dot matrix printers had fewer pins (ranging from seven to twelve), but as demand grew for higher quality print, more pins were added; modern dot matrix printers have a range of between eighteen to forty-eight pins, although the most common number is twenty-four.
These printers are most commonly used to print text, although they are also capable of producing very simple graphics (usually in bitmap form). The text or image being printed is represented by a pattern of dots (dot matrix pattern), which is created on the substrate by striking the relevant pins in the printhead against the ribbon and the substrate to create the required pattern. Dot matrix printers tend to print one line at a time, either as a serial dot matrix or a line dot matrix. In a serial dot matrix, the printhead moves horizontally across the substrate (by means of a stepper motor). This method is based on the idea of having one vertical column of pins in the printhead, with the column being roughly the maximum possible height of the characters that can be produced. Multiple columns (usually four) are actually used in the printhead to interleave dots during printing, which increases the density of dot placement (to improve print quality) and print speed, without the pins jamming together. In a line dot matrix, the printhead is as wide as the substrate and is fixed in place. This method is based on the idea of having one horizontal line of thousands of pins (although sometimes two are used to improve print quality and print speed by interleaving dots), which prints an entire line at a time as the substrate moves below the printhead.
Dot matrix printers are predominantly used to print monochrome text (usually black), but are capable of printing in colour. This requires a colour ribbon, which is divided into four sections (one for each colour, usually black and the three primary colours of red, yellow, and blue), and multiple passes when printing (one for each colour). When printing colour, either the printhead is moved (to strike the appropriate colour section) or the ribbon is moved (to align the appropriate colour section with the printhead). However, the range and quality of colour is extremely low and there are often issues with the ribbon deteriorating (as the ink in the black section will often slowly bleed into the colour sections).
These printers rose in popularity during the 1970s and 1980s, until they reached a peak in the 1990s. They had a number of advantages over other printing methods (some of which are still useful today), including the ability to create multiple copies of documents (carbon copies), processing continuous fanfold paper and individual sheets, using ribbon inks that run out gradually (they will fade rather than cutting off once a threshold has been met), and extremely low printing costs per page. This means dot matrix printing was (and still is, in some places) popular for marking product packaging, printing 2D barcodes, point of sale printers, continuous data logging, and multipart stationery and documentation (such as invoices).
However, dot matrix printing also has a number of limitations, which have seen it surpassed by other methods of printing (in particular, inkjet printing and thermal printing). The printhead can only contain so many pins, which limits the number of dots that can be printed per inch and so restricts the resolution that these printers are capable of producing. This process also has to rely on less effective methods of differentiating between areas of text (such as striking a character twice to create bold text), is slower than other printing methods and much louder (due to the use of an impact to print), and has the tendency to jam. There are also a number of issues related to the use of a ribbon; ink soaked ribbons vary in the quality of print they produce and may often produce print that fades over time; multi-strike ribbons allow ribbons to be used over and over again, but quickly decrease in quality; and single-strike ribbons produce a higher quality but can only be used once, which results in wasted areas, and they also have the unusual side effect of being a less private form of printing, as whatever has been printed remains visible on the ribbon.Go Back to Glossary