3.4 PRINTERS

 Printers are used for producing output on paper. There are a large variety of printers and printing devices. These devices can be classified according to the print quality and printing speed.

There are vast varieties of printers. Classification of these printers can be done by the technology used by them. These varieties of printers are:

Printing Technology : impact printers vs. non impact printers

Impact printers use variations of standards typewriter printing mechanism where a hammer strikes paper through inked ribbon. A nonimpact printer uses chemical, heat or electrical signals to each or induces symbols on paper. Many of these require special coated or treated paper to print characters on them.

3.4.1 Classification of printers on the basis of Speed

On the basis of speed printers are of following types:

1. Character Printer:

These printers can print only one character at a time. They work similar to that of the typewriter. The examples are Daisy Wheel Printer, Dot Matrix Printer and Inkjet Printer.

(a) Daisy Wheel Printer:

This printer is similar to a ballhead typewriter. This type of printer has a plastic or metal wheel on which the shape of each character is embossed.


A hammer presses the wheel against a ribbon, which in turn makes an ink stain in the shape of the character on the paper. Daisywheel printers produce letter quality print but cannot print graphics. The print quality of this impact printer is very low.

(b) DotMatrix Printer:

This is one of the most popular printers used for personal computing systems. These printers are relatively cheaper compared to other technologies and use impact technology. In the year, 1970s and 1980s, dot matrix impact printers were generally considered the best combination of expense and versatility, and until the 1990s they were by far the most common form of printer used with personal computers. Characters in this printer are formed by the combination of dots.


DotMatrix printer creates characters by striking pins against an ink soaked ribbon. Each pin makes a dot and combinations of dots form characters and illustrations. The moving portion of the printer is called the print head of Dot matrix printer.

Advantages:

  • · Dot matrix printers, like any impact printer, can print on multipart stationery or make carbon copies.
  • · Impact printers have one of the lowest printing costs per page. As the ink is running out, the printout gradually fades rather than suddenly stopping partway through a job.
  • · They are able to use continuous paper rather than requiring individual sheets, making them useful for data logging. They are good, reliable and ideal for use in situations where printed content is more important than quality.

Disadvantages:

  • · Impact printers are usually noisy.
  • · They can only print low resolution graphics, with limited color performance, and limited quality.
  • · Per minute page printing is low.

2. Line Printer

Line printers are used to print large amount of data. These are fast speed printers ranging from 300 to 2500 lines per minute. Examples are Drum Printers and Chain Printers.

3. Page Printer

These are very high speed printers which produce high quality output. Their speed ranges from 1025 pages per minute. These printers use modern Laser Printer technology and print whole page at one go. There are many varieties of laser page printers and so their prices from base label to high label.

3.4.2 Classification of Printers on the basis of Quality

The various types of printers based on print quality are as follows

(i) Inkjet

Printer: The Inkjet printer works on inkjet technology and produce better quality print than dot matrix printers. These print by spraying a controlled stream of tiny oink droplets accurately on the paper forming either dot matrix or solid characters. The printing quality of this printer is very good with the speed of 700 or more characters per second.

These are non – impact and hence are relatively less noise during printing process. This printer can be used to print in color and is easy to use.

Advantages:

Compared to other printers, inkjets printers have a number of advantages. These are:

  •  · They are quieter in operation than impact printers.
  • · They can print finer, smoother details through higher print head resolution
  • · It can produce photographicquality printing.


 Disadvantages:

Disadvantages of Inkjet printers are:

  • · The ink is often very expensive.
  • · Many intelligent ink cartridges contain a microchip that communicates the estimated ink level to the printer; this may cause the printer to display an error message, or incorrectly inform the user that the ink cartridge is empty.
  • · The very narrow inkjet nozzles are prone to clogging due to dried ink.

(ii) Laser Printer: This is a high quality, high speed and high volume technology printer. In laser printers, a laser beam is used to produce an image on a drum. The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure. Laser printers produce very high quality text and graphics but are very expensive. The technology used by them is same as that of photocopy machines. Speeds of laser printers can range from 10 pages per minute to 200 pages per minute. Laser printers are also called page printers, because they print whole page in one go.

Standard laser printers can be classified in two categories in terms of color:

  • · Monochrome laser printer, and
  • · Color laser printer.


 Monochrome laser printers use a single toner. Color laser printers use four toners to print in full color. These printers are about five to ten times as expensive as their monochrome siblings.

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