How Dot Matrix Printer Works
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Identification
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The dot matrix printer is an impact printer that makes the image of each letter through tiny wire-like pins pressing into a ribbon that strikes against the paper. Ink transfers to the paper at the point of impact. The mechanism is similar to an old-fashioned typewriter, which had hammers striking the ribbon. The dot matrix printer pins can be envisioned as many tiny hammers on a magnetized print head.
Method
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The electromagnet keeps the pins in place until a charge is made to a coil wrapped around the print wire, momentarily eliminating the magnetization and allowing the pin to spring forward. The pins print a pattern, or matrix, of dots on the paper, which creates letters and other characters as the print head moves across the page on a track. Each time the print head scans the page, it prints a slightly lower part of the line, until all the characters are completely formed.
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Paper
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The printer advances the paper, typically on a tractor feed, to begin each successive line of print. The tractor consists of sprockets on each end of the printer's roller bar, and dot matrix printer paper commonly has perforated edges with a row of holes to fit over the sprocket teeth, so the paper can move along with the roller.
Printer History
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Unlike another impact printer, the daisy wheel printer, dot matrix printers can change fonts and create bold and italicized characters without the need for changing a print wheel. Print quality is determined by the number of pins, ranging from nine to 32. Daisy wheel printers were commonly used for documents that needed a higher-quality appearance, called "letter quality." They were phased out by the popularity of inkjet and laser printers, which were much faster and quieter.
Advantages
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Unlike daisy wheel printers, dot matrix printers remain in use. Although they are very limited as far as graphics and color, and are slow and noisy, they have several advantages over inkjet and laser printers. They are more economical, durable and reliable, excellent for businesses that produce large amounts of printing that do not need to be high quality. The continuous-feed paper is perfect for printing lengthy data lists and for transaction processing. Impact printing allows dot matrix printers to make multiple copies, often necessary for invoices and bills of lading. Dot matrix printer ribbons can be used over and over, and unlike inkjets, they do not dry out easily, so they're still usable even if the printer is rarely utilized. Also unlike inkjets, a dot matrix printer ribbon fades gradually and does not suddenly run out in the middle of the job.
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Resources
- Photo Credit Shelley Moore photo
