Printers

A printer is a computer whose sole purpose is to convert electronic pulses into image on paper. Although printers come as separate devices, they are an integral part of a computer system. There are several types of printers available in the market. Following is description how these printers work.

Dot matrix printers

Also known as impact printers, dot matrix printers use a print head containing (Generally 9 to 24) that are forced to strike an inked ribbon against the paper to form a character. The character is actually formed by a series of dots. The print quality is increased when the numbers of pins are higher in print head.

Non-impact printers

Unlike impact printers, nothing is forced against the paper in non-impact printers. For the most part, non- impact printers use a technology called jet to form the image the paper. The print head in this case actually sprays a narrow stream of ink on the paper. Generally non-impact printers create a more fully-formed character than impact printers.

Laser printers

The term laser printer has become generic name to describe printers that utilized an electro –photographic process to produce image on paper. That fact is there are many ‘’laser printers’’ on the market which do not use laser beams to write image data. Instead, they utilize a bar of microscopic Light-Emitting Diodes (LEDs) or arrays of Liquid Crystal Shutters (LCS) to accomplish the same task. The mechanism of a laser printer involves many components and requires the Interaction of mechanical, electrical and optical technologies to work. A typical mechanism of a laser printer is as follows,

1.     Cleaning

Before the page can be printed, the photo-sensitive drum must be cleaned. The cleaning process is consummated by a rubber cleaning blade that gently scraps any remaining toner from the drum. The drum is then exposed to a lamp (Erase lamp) that will completely remove the last image.

2.     Conditioning

After the cleaning /erase process, the drum is no longer light sensitive and it needs charging. This is done by applying a uniform of negative charges (about 6000V) to the drum’s surface. This is done by a very thin solid wire called the primary corona located very near the drum’s surface.

3.     Writing

During the writing process a latent image is formed on the drum surface. The uniform negative charge from the previous step becomes discharged at precise point where the image is produced. The actual writing is done with the laser. Where the laser strikes the drum will now become less-negative charged.

4.     Developing

After the writing process the image is no more than an invisible array of electro-static charges on the drum’s surface. The toner is used to develop it. When the toner is ready to be applied, it is exposed to a cylinder (Developer cylinder) that contains a permanent magnet. It is here that the toner receives a strong negative charge. The area of low charge on the drum now attract the from the cylinder. This wills fill-in the electro-magnetic image. The other areas repel the equally negative charged toner. The drum now holds an image that is ready to be transferred to the paper.

5.     Transfer

At this point, the developed image is transferred to the paper. The paper is exposed to the transfer-corona which fixes a powerful positive charge to the paper that follows it to pry the negatively charged toner particles from the drum.

6.     Fusing

After the transfer process, the toner image is only lying on the surface of the paper, held by small charge. It must be permanently bonded to the paper it can be touched. The fuser assembly, along with the pressure roller, melts and processes the paper’s surface.

Leading printer brand’s