Printers


What is a printer?

Printer is a machine which is connected with computer to print any given data. The data may be a picture, or text etc. The data files may be of any format. Printers can be classified according to their printing methodology

Impact printers and Non-impact printers.

IMPACT PRINTERS:

These printers press formed character faces against an inked ribbon onto the paper. Examples of Impact printers are:

Line printer
Dot matrix printer

Line Printers

A line printer prints a complete line at a time. The printing speed of line printer varies from 150 lines to 2500 lines per minute with 96 to 100 characters on one line. The line printers are subdivided into two categories: Drum printers and chain printer.

Drum Printers

Drum printer consists of a cylindrical drum. One complete set of characters is embossed on all the print positions on a line, as shown in the Fig. The character to be printed is adjusted by rotating drum.

Chain Printers

In these printers chain with embossed character set is used, instead of drum. Here, the character to be printed is adjusted by rotating chain.

Dot Matrix Printers

Dot matrix printers are also called serial printers as they print one character at a time, with printing head moving across a line.

NON IMPACT PRINTERS:

Non impact printers can use any of the following techniques to print the image on paper. Laser techniques, Inkjet sprays Xerographic processes Electrostatic methods and Electrothermal methods

Examples of Non Impact printers are:

Ink-jet printer
Laser printer

Ink-Jet Printer 

In an inkjet printer, tiny nozzles spray ink onto the paper. Some inkjet printers are almost silent; others make strange, intermittent, loud beeps and clicks. Most of these printers are comparatively slow to produce an image, and the ink needs time to dry even after the image comes out, but the quality can be excellent.

Inkjet printers are available in single-color and multicolor designs. The best color machines produce photograph like images. A high-end inkjet printer costs roughly twice as much as a high-end dot-matrix machine, although some monochrome inkjets are as inexpensive as dot-matrix printers. Inkjet printers require periodic replacement of the ink cartridges. There are three or four of these, containing cyan, magenta, yellow, and sometimes black ink. Inkjet printers need a certain kind of paper; some papers have fibers that carry the ink along via capillary action, causing characters and images to blur. The finest, most expensive “bond” for typing might prove disastrous if used with an inkjet printer
 

Laser Printer

The line, dot matrix, and ink jet printers need a head movement on a ribbon to print characters. This mechanical movement is relatively slow due to the high inertia of mechanical elements

But, in laser printers these mechanical movements are avoided. In these printers, an electronically controlled laser beam traces out the desired character to be printed on a photoconductive drum. The exposed areas of the drum gets charged, which attracts an oppositely charged ink from the ink toner on to the exposed areas. This image is then transferred to the paper which comes in contact with the drum with pressure and heat, as shown in the Fig. The charge on the drum decides the darkness of the print. When charge is more, more ink is attracted and we get a dark print.

Colour Laser Printer

A colour laser printer works like a single laser printer, except that the process is repeated four times with four different ink colours: Cyan, magenta, yellow and black.

Laser printers have high resolution from 600 dots per inch upto 1200 per inch. These printers print 4 to 16 page of text per minute. The high quality and speed of laser printers make them ideal for office environment.

Advantages of Laser printer

  • The main advantages of laser printers are speed, precision and economy.
  • A laser can move very quickly, so it can write with much greater speed than an ink-jet.
  • As the laser beam has an unvarying diameter, it can draw more precisely, without spilling any excess ink.
  • Laser printers tend to be more expensive than ink-jet printers, but it doesn’t cost as much to keep them running.
  • Its toner power is cheap and lasts for longer time.

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