Laser printer

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Laser printer

• is a common type of computer printer that
  produces high quality printing, and is able to
  produce both text and graphics.
• The first laser printer was created by Gary
  Starkweather in 1978, by modifying a photocopier
• The slowest printers of this type print about
  four ppm, but the fastest print mass mailings can
  print at several thousand ppm.
• The primary principle at work in a laser printer
  is static electricity. Its the energy that makes
  clothes stick together, in the dryer or a
  lightning bolt travel from a thundercloud to the
  ground.

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DRUM

• The drum is a metal cylinder, usually made of
  aluminium. Its covered with a special material
  called photoconductor.
• This material has the property of being to store
  
  an electrical charge on
  its surface in darkness.
• In order to charge the drum, it is rotated
  against
  an insulated
  roller which has a voltage of 6000
  
  volts applied to it.

The drums photosensitivity can be damaged by
exposure to light. To accomplish this, red
plastic is placed over the lamps.
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toner

• It's an electrically-charged powder with two main
  ingredients pigment and plastic.
• it provides the coloring that fills in the text
  and images.
• This pigment is blended into plastic particles,
  so the toner will melt when it passes through
  the heat of the fuser.
• Toner consists of plastic resin particles and
  iron oxide (the particles that are affected by
  magnetic attraction and electrical charges).

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fuser

• Fuser is a pair of heated rollers.
• As the paper passes through these rollers,
  
  the loose toner
  powder melts, fusing with the fibers in the
  paper.
• The fuser rolls the
  paper
  to the output tray, and you have your finished
  page.

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Laser scanning assembly

• The traditional laser scanning assembly includes
  
• - A laser
• - A moveable mirror
  - A lens
• The laser receives the page data -the tiny dots
  that make up the text and images - one horizontal
  line at a time. As the beam moves across the
  drum, the laser emits a pulse of light for every
  dot to be printed, and no pulse for every dot of
  empty space.
• A Raster Image Processor (RIP) chip is used in
  laser printers to communicate raster images to a
  laser.

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The controller

• The printer controller is the laser printer's
  main onboard computer. It talks to the host
  computer (PC) through a communications port
  (USB).
• The controller must organise all of the data it
  receives from the host computer. This includes
  all of the commands that tell the printer what to
  do -- what paper to use, how to format the page,
  and etc

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Steps in printing

• Incoming data
• First, the computer sends data to the printer,
  Then the printer sends a signal back indicating
  it is ready for data.
• Drum preparation
• The drum must be cleaned to remove any traces of
  previous pages. First, a rubber blade wipes the
  excess toner from the drum, and then erase
  charged drum, electrostatically clean it by
  neutralizing left over electrical charges on it.
• Drum waiting
• As the drum cylinder rotates past the laser, it
  sweeps across the surface, turning on and off to
  neutralize certain areas to about -100 volts.
  These neutralized areas will be the spots where
  toner stick to the drum later in the process and
  then transfers to the paper

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• 4. Paper feed
• Feed rollers draw the paper into the printer
  from the paper tray.
• 5. Toner pickup
• As the paper is being drawn in, the toner is
  being applied to the drum.
• Toner transfer to paper
• 7. Fusing the toner to the paper
• Fusing is basically melting the toners plastic
  particles so they stick to the fibers in the
  paper.

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The path of a piece of paper through a laser
printer
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Advantage of laser printer

• The main advantages of laser printers are speed,
  precision and economy.
• A laser printer can move very quickly, with much
  faster speed than an ink jet printer
• And because the laser beam, it can draw more
  precisely, without spilling any excess ink.
• toner powder is cheap and lasts a long time,
  while you can use up expensive ink cartridges
  very quickly.
• The End