Transcript ppt - AD Book Enterprises

10/24: Output: Printers
• Types of printers: laser, inkjet, dot-matrix printers
• Other types: plotters, label printers, digital
presses, photo printers, electrostatic printers, LED
printers
• How color printing works
• What to look for in a printer
Printers: General
• Printers
– two main groups:
impact (dot-matrix, daisywheel) &
nonimpact (laser, inkjet,
thermal)
– other types: plotters, label
printers, digital presses, photo
printers, large-format printers
– color printing
dot matrix printer image courtesy of epson.com, others courtesy of hp.com
Impact Printers
• Dot-Matrix printers: Pins are
pushed by solenoids to hit a
ribbon in front of the paper.
• Daisy-Wheel printers: Letters
are pushed to hit the ribbon in
front of the paper.
• Stamp ink onto the paper.
• Advantages: cheap, reliable,
low CPU demand, multipleform copying
• Disadvantages: loud, slow
images courtesy of How Computers Work and Brother.com
Non-Impact: Inkjet Printers
• The ink cartridges have tiny
heating elements that cause
microdrops of ink to heat up
and expand, shooting out of
the nozzle and onto the
paper.
• Advantage: cheap color
printing
images courtesy of HP.com and How Computers Work
The Ink Cartridge
• The ink cartridge(s)
–
–
–
–
nozzle
firing chamber
path from reservoir
thin-film resistor
Cross-section of a nozzle.
How does the ink get out? One of two ways:
The Thermal method or the Piezo-Electric method.
How the ink gets out: thermal method
Nozzle
Firing
Chamber
Resistor
• Used by Hewlett
Packard & Canon
• A thin-film resistor
is heated by electric
current.
• The resistor heats up
the ink that is next to
it.
How the ink gets out: thermal method
Nozzle
Firing
Chamber
Resistor
• The ink- now
gaseous - expands,
forming a bubble.
• The bubble pushes
out the rest of the
ink in the firing
chamber.
How the ink gets out: thermal method
• The resistor cools,
causing the bubble
Nozzle
to shrink.
Firing
• The shrinking
Chamber
creates a vacuum,
which draws new
Resistor
ink from the
reservoir.
• The piezo method uses a flexing, swelling
crystal instead of heat to push the ink out.
Laser Printers
• Deposit toner onto the paper,
then melt it to make it
permanent.
• Cheaper by the day – per
page printing costs are very
low.
• Faster than inkjet printers.
• Very quiet.
images courtesy of How Computers Work
Laser printing
• The pattern to be
printed is set up in
a grid of black
areas and white
areas.
• The laser beams,
horizontal line by
horizontal line, this
grid of dark areas.
Laser printing
• When the drum is
hit with the laser
beam, it
electrically charges
the coating at that
spot.
• In HP & Canon
printers, the
coating is
positively charged.
Laser printing
• As the drum rolls
by, the positively
charged parts of
the coating on the
drum attract the
toner particles.
Laser printing
• The sheet of paper
touches the drum
coated in toner.
• The toner jumps to
the paper from the
drum because the
paper is more
strongly charged
than the drum.
Laser printing
• The paper, with the
toner particles,
goes to the fusing
rollers. The rollers
use pressure and
heat to bind the
toner to the paper
permanently.
How Color Printing Works
• subtractive color
– monitors use additive
color: all colors
combine to get lighter
shades
• printers combine colors
to get darker shades
• all colors together
create black
Looking at printers in ads
• Go to http://www.buy.com
• things to note when comparison shopping:
–
–
–
–
–
–
–
what YOU will be using the printer for
ppm (pages per minute) in b&w, color
size limitations of paper
paper tray capacity
price (and price of ink/toner cartridges)
dpi (dots per inch) – print quality capabilities
(inkjets) type of black printing: separate cartridge?