Printers

The printer is computer peripheral,
& output device that accepts text
and graphic as input,
& prints or illustrations on paper as
a hard copy in the form of
documents or transparencies etc..

Types
There are four major types of
printers.
1.
2.
3.
4.
Impact printer
Sprayed-ink printer
Laser printer
Plotters.

Impact Printers
1.
2.
Daisy Wheel
Dot Matrix

Daisy wheel printer

Daisy wheel
The printer look like daisy contains a disk made of
plastic or metal on which letters and symbols are
placed on each patel.
When printer needs to print a character, it
sends the signal to mechanism called printhead , the
printhead rotates the daisy wheel until the desired
letter is in place and facing the paper then a
electromechanical hammer called Solenoid strikes the
back of the character contained petal, forcing the
character to hit an ink ribbon, leaving an impression of
the character on the paper.

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Daisy wheel printing speed is
measured in character per second
and
standard speed is 10 to 50
characters per second.
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Printer work like typewriter and
best in multi-copy applications, it can’t
print graphics.

Dot Matrix
This is an other type of impact
printers here printhead contains row
of pins.
The pins are wrapped with coils of
wire to create solenoid, to trigger a
particular pin the printer controller
sends a signal to printhead , which
energize the wires, this makes wires
into electromagnet which repel the
print pin towards ribbon and printing
dots in column and rows and making
letters and numbers on paper.

Initialy 9 pins used but later
17 and 24 pin models also
introduced for fine output
print.
Its standard speed about
50 to over 500 cps.

Dot Matrix

Sprayed-ink Printers
1.
2.
Inkjet
Bubble jet

Inkjet
Inkjet printers considered as sprayed-ink on paper.
this uses cartridge which contains ink, pump
and a ink nozzle to complete printing.
when computer send print command then
printhead at cartridge energize Piezo-actuator
which spraying ink then nozzles makes shape
letters, words or images on paper.
Ink-jet printers are capable of producing high
quality print. A typical ink-jet printer provides a
resolution of 300 dpi, also newer models offer higher
resolutions.

Inkjet

Bubble jet printer
Bubble-jet printers use special heating
elements to out the ink.
Like inkjet printers this type of printer also
uses cartridge which have several small
chambers inside, bottom of each chamber
have a small pinholes, these pinholes are
used to spray ink on the page and print
characters and images with fine
resolution.

If particular chamber needs to spray ink,
then electric signal is sent to heating
element, when element is energized,
it creates vapours, then these vapours push
ink towards pinhole and forms a bubble of
ink.

Bubblejet

Laser Printers
Laser printers accept computer signals and
convert it to laser beam to produce an
image on a drum, toner touches drum and
coat with inked powder and finally convert
this inked image to a paper.
Photocopiers also work on same procedure.
Laser printer also called page printers and
use memory to print high-resolution text &
graphics outputs, resolution ranges from
300 to 1200 dpi. The speed of laser printers
ranges from about 5 to 20 ppm.

Printer Components
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Printer Controller unit
Corona wire unit
Laser beam converter unit
Photosensitive drum unit
Toner unit
Paper feeding unit
Fuser unit
Exit rollers unit

How Laser printer works

1.
Text or graphics base data stream is sent to
the printer.
2.
The printer controller circuit receive input
signals and manages how to print this data.
3.
Here this controller circuit done two jobs
first it activates the corona wire. This is a
high-voltage wire generate static electric
charge to anything nearby, second
computer data signals converts into laser
beam.

4.
5.
The corona wire charges up the
photoreceptor drum so the drum gains a
positive charge spread uniformly across its
surface.
The circuit activates the laser to draw the
image of page onto the drum using mirror,
when laser beam hits the drum, it removes
positive charges and creates negative
charges on drum and transfer image on the
drum.

6.
An ink roller (toner) touching drum and
coats it with tiny particles of powdered ink
then this inked image of the page remains
on the drum.
7.
A sheet of paper from a hopper on the other
side of the printer feeds up toward the
drum. As it moves along, the paper is given
a strong electrical positive charges by
another corona wire.

8.
When the paper reaches near the drum, its
positive charges attracts the negative
charges away from the drum, then inkedimage is transferred from the drum to paper
surface.
9.
The inked paper passes through two hot
rollers from fuser unit. The heat and
pressure from the rollers press toner
particles permanently into the paper.
10. Finally exit rollers get printed paper out, this
output is hot for a while.

Laser print processes
1.
EP print process:
This technology uses a
combination of static electric
charges, laser light and toner.
2.
HP print process:
This technology is relatively
same
as EP but it uses charging
roller
instead of corona wire and
developing roller in the toner.

Laser print processes
3.
LED print process
This technology uses
LEDs instead
of laser light, and
these LEDs are near to drum,
having advantage of low cost and
laser beam
hazardous.

Plotters
Plotters are large-scale printers, These are
commonly used for technical drawings such
as engineering drawings or architectural
designs.
The two basic types of plotters are called
1.
2.
Flatbed plotters
Drum plotters.

Flatbed Plotters
Flatbed plotters one of the graphics
output device that draws by moving a
pen in both horizontal and vertical
directions over a sheet of paper; the
overall size of the drawing is limited by
the height and width of this bed.

Flatbed Plotters

Drum Plotters
Drum plotters, also called upright plotters,
this type of plotters are vertically positioned.
Printing image is on a drum where paper
rolls on it and making a fine image, text or
design as large scale printing.

Drum Plotters

Printer Characteristics
Color:
Color printers are more expensive to
operate since they use two ink
cartridges one is colored and other is
black ink, these are important for maps
and designs.
Resolution:
Printer resolution (sharpness) is usually
measured in dots per inch (dpi),
standard resolution is 300 - 600 dpi.

Printer Characteristics
Speed:
Speed of printer is based on page sent,
Color printers are slower.
Latest and expensive printers are
much faster.
Memory:
Memory used to store print commands
sent by computer, Most printers come
with a small amount of memory that
can be expanded by the user.

Other Printers

Portable printers
Portable printers are
lightweight using a battery
instead of power
from the
computer.
Usually they maintains
basic print resolutions
suitable for plain text
printing.

Digital Photo Printers
Many middle range
printers print photo
quality images.
Usually color printers,
specially photo print
with greater resolution
& image quality.

Network printer
This type of printer is
installed in LAN or
Wireless LAN (WLAN)
environment and
common printing facility
to all network users.

Multifunction printers:
This type of printer contains
High-quality color
printing, Fax machine,
Color copier,
Scanner,
Telephone.
facilities in one device.

3D Printers
This type of printer
creates computer-aided
design 3-D applications.
The printer is fast,
versatile and simple,
allowing engineers to
produce a range of
concept models and
functional test parts of
any design.