IS 148 A Certification, Hardware

1
IS 148 A Certification, Hardware

• Chapter 15
• Printers

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Printer Types

• Dot Matrix (impact)
• Ink Jet
• Dye-Sublimation
• Thermal
• Laser and LED
  

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Dot Matrix Printers

• Pins strikes the ribbon and transfer ink to paper
• 7 pin
• 24 pin (letter quality)
• These print heads get hot and will burn skin
• Paper moves through the printer using a tractor
  feed mechanism.
• Are the only style of printer that can print on
  multiple part paper forms.
• Still exist in point of sale equipment

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Dot Matrix

• Uses a print head containing a number of pins.
• These pins may also be called print wires.
• Pins are forced out of the print head to strike
  the ribbon.
• Most print heads have 9 or 24 print wires.
• Uses Tractor feed mechanism to pull the paper
  through the printer.

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Inkjet Printers

• Inkjet printers create printouts by squirting ink
  out of special inkjet cartridges.
• These printers use either liquid ink or a solid
  wax-based ink cartridge.
• Print in black and white or color.
• Inkjet printers are non-impact printers.
• Inkjet printers use friction feed to move the
  paper through the printer.
• Inkjet printers are sometimes called page
  printers because they process a whole page before
  beginning to print.

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Thermal Ink Jet Printers

• Most liquid inkjet printers and all solid inkjet
  printers use a thermal process to eject ink onto
  the paper.
• In this process the heating element heats up,
  boiling the ink.
• A tiny bubble of ink forms on the end of the
  print nozzle.
• When the bubble pops electrically charged plates
  deflect the ink onto the paper.
• An inkjet print head contains between 300 and 600
  nozzles, each about the diameter of a human hair.
• Hewlett-Packard and Cannon use this process
  

7
Epson Crystal Ink Jet

• Epson printers use a proprietary technology that
  uses a crystal pump in the ink cartridge.
• When current is passed through the crystal it
  flexes and squeezes ink through the nozzles.
• Size and position of the ink are controlled by
  the amount of current.
  

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Dye-Sublimation Printers

• Sublimation To change from a solid to a vapor
  and then back to a solid.
• Uses rolls of heat sensitive plastic film that
  contains sections of cyan, magenta and yellow
  dye.
• The print head moves across the film, vaporizes
  the dyes.
• The dyes soak into a special paper before cooling
  and returning to a solid.
• These printers produce a very high quality color
  output.

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Thermal Printers

• There are two common types of thermal printers
• Direct thermal Uses heated pins to burn dots
  into the surface of special paper.
• Thermal wax transfer Works similarly to
  dye-sublimation printers except it uses film
  coated with colored wax.
• Thermal wax printers do not require special
  paper.
• Do not provide as good of a quality as the
  sublimation printers.

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Laser Printers

• Laser printers are built upon photocopy
  technology.
• Laser printers are almost identical to a photo
  copy machine.
• In short they work by applying different polarity
  charges and voltages to a drum, toner and the
  paper.

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LASER and LED Printers

• Laser printers rely on the photoconductive
  properties of certain materials.
• Materials that exhibit photoconductive
  properties will conduct electricity when exposed
  to light.
• This is the same process used in copy machines.
• Laser and LED printers are the same except for
  the source of light.
  

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LASER Printer Characteristics

• Nonimpact
• Page Printer
• Print mechanism never touches the paper
• Images the entire page before printing
• May allow duplex printing
• Resolutions upto 2400 x 2400 dpi
• Color Laser printers are available
• LASER Light Amplification by Stimulated Emission
  of Radiation.

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Content of the Toner Cartridge

• Toner
• Drum
• Conditioning Roller
• Developing Roller
• The first 4 steps of the printing process use
  components that are contained in the cartridge.
  

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Laser Printing Terms

• Photosensitive Drum
• Erase Lamp
• Primary Corona Wire Laser
• Toner
• Transfer Corona
• Fuser

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Toner

• The toner is a fine powder made up of plastic
  particles bonded to iron particles.
• The toner has a charge between 200 and 500
  volts.
• Particles of toner will be attracted to the less
  negatively charged areas of the drum where the
  laser wrote.

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Photo Sensitive Drum

• An aluminum drum coated with a photosensitive
  compound.
• Is contained in the toner cartridge
• Surface of the aluminum drum is electrically
  neutral.
• Should not be exposed to direct light.
• If scratched it is necessary to replace the toner
  cartridge.

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Erase Lamp

• Exposes the entire surface of the photosensitive
  drum to light making the photosensitive coating
  electrically conductive.
• The erase lamp leaves the conductive coating on
  the drum electrically neutral.
  

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Primary Corona Wire

• Located very close to the photosensitive drum but
  does not touch the drum.
• Regulates the charging of the photosensitive
  material on the drum.
• Passes a very high static charge to the drum
  surface.
• The drum will receive a uniform negative charge
  between 600 and a -1000 volts.
  

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Transfer Corona Wire

• Gives the paper a positive charge.
• The paper then draws the negative toner particles
  to the paper.
• To prevent the paper from being attracted to the
  drum a static charge eliminator removes the
  charge from the paper.
• This wire is subject to prone build up and should
  be cleaned with a special tool
• Do not touch this wire with your hands.
  

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LASER or LED

• The laser beam is the printers writing mechanism
• Any area on the drum that is struck by the laser
  beam is discharged to about a 100 volts.
• Any area struck by the laser now looks positive
  with respect to the drum which is at a -600 to
  -1000 volts.
• The laser writes a positive image to the drum as
  opposed to a negative.

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Fuser

• Used to permanently attached to the paper.
• The particles are fused to the paper using two
  rollers
• A pressure roller
• Heated roller
• Pressure roller presses on the back of the page
  while the heated roller presses on the front of
  the page melting the plastic particles, toner,
  into the page.

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Caution

• If a toner cartridge is dropped and toner escapes
  it can cause eye damage.
• Persons wearing contact lenses are at a high risk
  of getting toner behind the lens and damaging the
  eye.
• Dont use compressed air on laser printers.
• Toner cartridges maybe considered hazardous
  waste.

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The six steps of laser printing

• Clean the drum
• Charge the drum (Conditioning)
• Write the image
• Develop the image
• Transfer the image
• Fusing the image

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Steps of Laser Printing
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Step 1 Cleaning

• The drum is cleaned of any residual toner and
  electrical charge.

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Step 2 Charging the drum

• Drum is conditioned by the corona wire to contain
  a high negative electrical charge.
• Drum is charged to between -600 and -1000 volts

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Step 3 Writing the image

• A laser beam is used to discharge the high
  negative charge down to a lower charge, only in
  those places where toner is to be attracted.
• Each point contacted by the laser light is
  reduced to 100 volts.
• Remember the toner is at a -200 to -500 volts
  

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Step 4 Developing the image

• Toner is placed onto the drum where the charge
  has been reduced.
• Toner is attracted to the part of the drum with
  the more positive charge

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Step 5 Transferring the image

• A strong electrical charge draws the toner off
  the drum onto the paper.
• A static charge eliminator removes the positive
  charge from the paper.
• Gravity and a weak electrical charge is all that
  holds the toner to the paper at this point.
  

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Step 6 Fusing the image

• Heat and pressure are used to fuse the toner to
  the paper.
• Fusing rollers are heated to about 180 degrees C
  or 356 degrees F.
  
• Toner is melted into the paper
• After the fusing step the process begins again
  with cleaning.

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Other Laser Components

• Power Supplies
• Turning Gears
• System Boards
• Network Interface
• Ozone Filter
• Sensors and Switches
• Duplexer
• Finishers
  

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Power Supplies

• Laser printers typically have two power supplies
• Primary power supply that provides power to
• Motors
• System electronics
• The laser
• Transfer corona
• High-voltage power supply that provides power
  only to the primary corona wire.
• Always turn off a laser printer before you open
  it except when installing a new toner cartridge
  or replacing paper.
  

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Turning Gears

• Gear systems are used to
• Pick up and feed paper
• Rotate the photosensitive drum
• Move the laser light and reflecting mirror
• Agitate and distribute toner
• Move fuser rollers
• Most LASER printers have two or three gear boxes
• These boxes are easily replaced as a complete
  assembly.

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System Board

• Every printer has at least one system board
  containing
• Main Processor Chip
• RAM
• ROM
• Some printers will have more than one electronics
  board.
• May be possible to add RAM
• Memory Overflow errors
  

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Network Interface

• Many laser printers include a network interface.
• The printers include software that allows them to
  be connected directly to a network and serve as a
  network printer.

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Ozone Filter

• The corona wires generate Ozone.
• This is not harmful to humans but high
  concentrations will damage printer components.
• Ozone filters should be replaced each time a new
  toner cartridge in installed.

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Sensors and Switches

• Sensors are used to detect
• Paper jams
• Empty paper trays
• Low toner levels
• Switches are used to detect conditions like open
  doors or missing covers.

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Duplexer

• These are mechanical paper feeding devices that
  enable printing on both sides of the paper.
• May be attached to the front or back of the
  printer.
• Duplexers may take the place of a paper tray.

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Finishing operations (finishers)

• Collate
• Staple
• Bind
  

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Printer Connections

• Printers may be connected to a PC via
• Serial Port
• Parallel Port
• USB
• FireWire
• Network
• Hardwire
• Wireless
  

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Comparisons

• Serial
• Typical maximum speed 57600 bps
• Cable lengths up to 25 feet
• 9 or 25 pin
• Parallel ports
• Typical maximum speed for a standard port 150
  KBps.
• Cable length lt 6 feet
• 25 pin
  

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IEEE 1284 standard parallel port

• Attempts to deal with both the poor performance
  and lack of standardization of common pc parallel
  ports.
• Data transfer is half duplex
• Data transfer modes
• Compatibility mode
• Nibble Mode
• Byte mode

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Compatibility / Centronics mode

• Uses typical printer cable with a Centronics plug
  and a 25 pin D-shell connector
• Advantage is backward compatibility
• Disadvantages are
• Data flow is only from PC to printer
• Constant attention from CPU for error checking
  and handshaking
• Transfer speed is limited to about 150 KBps.
• 
  

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Nibble Mode

• Simplest way to transder data in the reverse
  direction.
• Provides a limited form of bidirectional
  communication with any parallel port.
• Uses 4 of the 5 status wires in the parallel
  cable to transfer one half of an eight bit word
  at t time.
• A word is 8 bits so a nibble is 4 bits
• Speed is 50 KBps
  

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Byte Mode/Enhanced Bidirectional

• Enables reverse direction (peripheral to pc)
  communications.
• Requires extra hardware to handle negotiation
  between pc and devices
• Referred to as Enhanced Bidirectional Ports
• Two way communication at data rates of 150 KBps.
  
  

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Enhanced Parallel Port (EPP)

• Maintains backward compatibility
• Used by peripherals other than printers that
  require two way communications.
• Transfer rates of 500 KBps to 2 MBps.

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Extended Capabilities Port (ECP)

• Designed for high performance parallel
  communications that involve moving large amounts
  of data with minimum monitoring.
• Examples are large printing jobs going out to a
  printer or an image coming in from a scanner.
• Uses a 641 compression scheme
• Many of these ports use DMA channels
• Good for handling large blocks of data via DMA
  channels

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CMOS Port Check

• Cell port settings can be verified or changed in
  CMOS

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Raster Graphics

• Another term for bitmapped graphics.
• Bitmapping stores an image in memory using rows
  and columns of dots.
• Each dot is represented by one or more bits of
  data
• Printers and scanners typically use raster
  graphics to represent data.
  

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Vector Graphics

• Math formulas are used to represent the various
  parameters of an image.
• Vector graphics can easily change size with out
  losing their original shape
• Vector Graphics are used to create scalable
  fonts.
  

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Fast Serial Printers

• USB is the most common type of printer connection
  found on new printers.
• FireWire connections are also now available on
  many new printers.
• Infrared Printers allow printing with out
  hardwiring the computer to the printer.
• Infrared connections are limited to line of sight
  over no more than one meter. (39 Inches)

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Network Printers

• Network printers fall into two categories
• Shared Printers connected to a workstation pc
  serving as a print server.shared by other pcs on
  the network.
• Network Printers Attached directly to the
  network through an integrated NIC or dedicated
  print server.
• True network printers are equipped with powerful
  microprocessor and large amounts of onboard RAM.
  

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General Print Quality Issues

• Print job never prints
• Incorrect paper size
• Garbage characters in printout
• Printer not responding

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Print Job Never Prints

• Double click on the printer icon to see the
  status of all print jobs for that printer

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Print Spooler Status

• If the print job never prints check the printer
  status to see what jobs are waiting to print and
  their print status.
• Spoolers can become corrupt due to lack of disk
  space to store print jobs
• Delete all print jobs and try again
  

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Incorrect Page Size

• A print job that comes out sized incorrectly
  usually points to a user mistake in setting up
  the print job.
• Check page setup and reprint
• If problems continue uninstall printer drivers
  and reinstall known good drivers.

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Garbage Characters in Printout

• Misaligned or garbage printout typically indicate
  corrupted or incorrect printer drivers.
• Verify the correct drivers
• Uninstall and reinstall printer drivers