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Types of computer printers and how they work:
I. Impact Printers: These printers must have a mechanism that actually touches the paper in order to create an image. These printers are inexpensive to operate, but are only useful for text (particularly for multi-part forms), not graphics, and are rather noisy and relatively slow. There are basically two types of impact printers:
A. Dot Matrix Printers: These printers use a series of small pins (between 9 and 24) to strike a ribbon coated with ink, causing the ink to transfer to the paper at the point of impact. Not used as often any more, mostly for specific purposes, such as multi-part forms.
B. Character printers, sometimes called “Daisy Wheel” printers: These are basically computerized typewriters, having a rotating wheel or series of bars with actual raised characters embossed on the surface so that, when a character is struck against the ink ribbon, the character’s image is transferred to the paper. These printers are slow, noisy and pretty much obsolete.
II. Non-Impact Printers:
A. Inkjet printers: Any printer that places extremely small droplets of ink onto paper to create an image. The dots are extremely small; usually between 50 and 60 microns in diameter, smaller than the diameter of a human hair (which is about 70 microns). The dots are positioned very precisely, with resolutions of up to 1440 x 1440 dots per inch, and they can combine different colors to create photo-quality images. The most popular type of inkjet printer is the “bubble jet,” in which tiny resistors create heat which vaporizes the ink to create a bubble the expansion of which causes a droplet to form and eject from the print head. A typical bubble jet print head has either 64 or 128 tiny nozzles, all of which can fire droplets simultaneously. Since their introduction in the 1980s, inkjet printers have become most common due to their low cost and performance, although the per-page cost for the ink is substantially greater than other types of printers. [For a detailed illustrated discussion of exactly how an inkjet printer works, see this LINK.] Inkjet printers include various parts, including the print head (usually part of the ink cartridge), the stepper motor (which moves the print head/cartridge back and forth across the paper and parks it when not in use), a belt, stabilizer bar, paper tray & feeder, rollers, power supply, various ports and control circuitry using microfluidics measurement. The following is a photo of a typical printer head in an inkjet printer:
B. Laser printers: These printers use dry ink known as “toner”, which is charged with static electricity, then heat, to place and bond the ink, which may contain colors, onto the paper. Higher initial cost, but substantially lower per-page cost thereafter. [For a detailed illustrated discussion of exactly how a laser printer works, see this LINK.]
C. See also, Plotters, a special type of printer that prints blueprints and other graphics on large paper.
III. The following additional types of non-impact printers are used for more specialized purposes and are not generally sold for residential use:
A. Solid Ink: These printers use sticks of a wax-like ink that is melted and applied to the paper.
B. Dye sublimation: These printers use a roll of transparent film consisting of sheets of red, blue, yellow and gray colored cellophane laminated together. The film passes over a heating element which varies in temperature depending upon the amount of a particular color to be applied. The printer makes a complete pass over the paper for each of the basic colors to build the final image.
C. Thermal wax: Similar to dye sublimation, but this type of printer uses a ribbon of alternating color bands which pass in front of print head that has a series of tiny heated pins, which cause the wax to melt and then adhere to paper.
D. Gel: In 2005, a new “Gel” printing technology was unveiled in Japan. Ricoh printers spray a viscous liquid gel that gelatinises and dries almost instantly upon contact with paper, minimizing bleeding and smudging of images and is also water and sunlight resistent, resulting in increased document durability. Three years later, Xerox introduced a “cured gel ink technology” for the purpose of printing on plastic and foil, taking digital printers primarily to the packaging market. This still appears to be a specialty technology, not widely adopted in the consumer printing arena.
E. Thermal autochrome: These printers have the color in the paper instead of the printer. The color layers in the paper are activated by the application of a specific amount of heat. Again, the printer head passes over the paper multiple times at different degrees of heat in order to build the final image.
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