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Inkjet printers are one of the most common type of printers in use these days. Their advantages include a very low inital cost, as little as $50 for a low-end model such as the EPSON Stylus C40UX, significantly less then the cost of a laser printer, and good color output. Disadvantages include a relatively high cost per page, usually around 10 times the cost of laser printers, and relatively slow pages per minute speeds of around 4 to 8ppm for black and white and 2 to 4ppm for color.

Most inkjets work using thermal technology where tiny dots of ink are fired at the paper through heat. A small resistor heats the ink in a chamber untill a bubble is formed. This bubble forces the ink out of the chamber onto the paper. Multiple chambers are arranged on the print head and fire as the print head is moved back and forth across the paper. In most color inkjet printers their are chambers for cyan, magenta, yellow and black inks, the CYMK colors. Some printers leave out the black and instead form it by mixing cyan, magenta and yellow. However doing this can't give a true black as the colors never really mix properly; it's also wastefull of expensive color ink.

A slightly different method used by Epson used a piezo crystal instead of a heating resistor. The peizo crystal changes shape in response to electric current, this forces ink out of the nozzle just like the heater-based printers. However the peizo crystal provides better control then a heating resistor allowing for smaller dot sizes and higher resolution.

The two main factors affecting printer quality is the resolution, measured in dpi, (dots per inch) and the number of levels, or graduations, that can be printed per dot. Most printers opt for a trade-off, some opting for higher resolution and others opting for more levels per dot. Business users usually need high resolution for crisp letters, graphics designers need more graduations to give more realistic color. Most printers can print up to 1440x720dpi (1440 dots horizontally, 720 vertically) with around 4 to 16 levels of color per dot. Some printers can print multiple drops of ink on one dot. For instance printers with Hewlett-Packard's PhotoREt colour layering technology can print over 30 individual drops of ink per dot, allowing for thousands of possible colors per dot.

Two types of ink are commonly used in inkjet printers, slow drying and deep penetrating and fast drying ink. The former takes up to 10 seconds to dry, this makes it rather prone to smudging and more sutable for monochrome printing. The latter drys around 100 times faster and is better suted for color printing as when different inks are mixed they need to dry quickly to avoid blurring. Nearly all inks used today are water based. This unfortunately poses problems with smudging and running. It also means that like most printed materials the ink is not very water resistant. Laser printers, with their "baked-on" toner, are better in this respect.

Most good printers will have two cartridges, one for black ink and one for color. This saves on costs by allowing you to just replace the black, or color, ink if that's all you've run out of. Some printers even go and seperate the color cartidge into seperate cartridges for the cyan, magenta and yellow. Another factor is the actual print head. Some printers, usually heat based printers, have integrated ink cartidges and print heads. Others, such as many of Epson's peizo crystal based printers, have a permanent print head. Some even have both a replacable print head and ink cartidge! Print heads can tend to clog up, especially if the printer isn't used regularly, so a replacable print head can be an advantage. However the print heads usually will last for a lot longer then the ink and a integrated ink/print head will cost more.

-- generic-man notes that most cheap printers are sold at below cost, so that the manufacturers recoup the costs when you buy ink cartridges. Ever wonder why those third-party cartridges are never sanctioned by the manufacturers?

For photo-quality output most inkjet printers require special high-quality coated or glossy paper which can be very expensive. For most monochrome uses however plain copier paper is sufficient. Most manufactures sell special papers that are optimized for the specific technologies used in their printers, though this paper tends to be significantly more expensive then generic papers. For instance paper can be pre-conditioned with a agent that helps bind the pigment to the paper. However these agents are specific to whatever type of ink is used by that manufacture.

Other alternatives to inkjet printers include laser printers, dot matrix printers and dye sublimination printers.

  1. "The PC Technology Guide - Inkjet Printers" - http://www.pctechguide.com/13inkjets.htm
  2. "How Inkjet Printers Work" - http://www.howstuffworks.com/inkjet-printer.htm

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