Dot-matrix printing technology

Impact printers are the oldest printing technologies still in active production. Some of the largest printer vendors continue to manufacture, market, and support impact printers, parts, and supplies. Impact printers are most functional in specialized environments where low-cost printing is essential. The three most common forms of impact printers are dot-matrix, daisy-wheel, and line printers.

Among the above three common forms of impact printers, the dot-matrix printing technology is quite simple. The paper is pressed against a drum (a rubber-coated cylinder) and is intermittently pulled forward as printing progresses. The electromagnetically-driven printhead moves across the paper and strikes the printer ribbon situated between the paper and printhead pin. The impact of the printhead against the printer ribbon imprints ink dots on the paper which form human-readable characters.

Dot-matrix printers vary in print resolution and overall quality with either 9 or 24-pin printheads. The more pins per inch, the higher the print resolution. Most dot-matrix printers have a maximum resolution around 240 dpi (dots per inch). While this resolution is not as high as those possible in laser or inkjet printers, there is one distinct advantage to dot-matrix (or any form of impact) printing. Because the printhead must strike the surface of the paper with enough force to transfer ink from a ribbon onto the page, it is ideal for environments that must produce carbon copies through the use of special multi-part documents. These documents have carbon (or other pressure-sensitive material) on the underside and create a mark on the sheet underneath when pressure is applied. Retailers and small businesses often use carbon copies as receipts or bills of sale.

Of all the printer types, however, impact printers have relatively low consumable costs. Ink ribbons and paper are the primary recurring costs for impact printers. Some Impact printers (usually line and dot-matrix printers) require tractor-fed paper, which can increase the costs of operation somewhat.

As of 2005, dot matrix impact technology remains in use in devices such as dot matrix printer mechanisms used in cash registers, ATM, and many other point-of-sales terminals. Thermal printer mechanisms are gradually supplanting them in these applications, but because dot matrix printer mechanism can produce carbon copies, dot-matrix impact printer mechanism are still used to print multi-part stationery, for example at bank tellers, and other applications where use of tractor feed paper is desirable such as data logging and aviation.