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Printing - Laser Printers

charged drum light paper

Laser printers currently accommodate the high volume printing needs of many large organizations, and meet the more modest requirements of individuals and small businesses. In laser printing, electronic signals describing the document are first sent from the desktop publishing computer to the printer's logic board. Printing fonts are next loaded into the printer's memory. The printer's central processing unit then sends light signal instructions to a laser, which focuses a beam of light on a rotating drum in the printer. This beam is turned on where black dots will appear, and turned off where the page will remain white.

The rotating drum is coated with a negatively charged, light sensitive material that becomes positively charged wherever the light strikes it. Negatively charged toner particles are attracted to positively charged regions on the drum. This creates the image to be printed on the drum.

A sheet of paper is drawn from the printer's paper tray so that it passes between the drum and a positively charged wire. The positively charged wire draws the negatively charged toner particles from the drum to the paper. Finally, the toner is bonded to the paper as it passes through two rollers that are heated to about 320°F (160°C).

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