A printer is any device that prints text or illustrations on paper. There are many different types of printers. In terms of the technology utilized, printers fall into the following categories:
1. daisy‐wheel: Similar to a ball‐head typewriter, this type of printer has a plastic or metal wheel on which the shape of each character stands out in relief. A hammer presses the wheel against a ribbon, which in turn makes an ink stain in the shape of the character on the paper.Daisy‐wheel printers produce letter‐quality print but cannot print graphics.
2.
dot‐matrix: Creates characters by striking pins against an ink ribbon. Each pin
makes a dot, and combinations of dots form characters and illustrations.
3.
ink‐jet: Sprays ink at a sheet of paper. Ink‐jet printers produce high‐quality
text and graphics.
4.
laser: Uses the same technology as copy machines. Laser printers produce very
high quality text and graphics.
5.
LCD & LED :Similar to a laser printer, but uses liquid crystals or
light‐emitting diodes rather than a laser to produce an image on the drum.
6.
line printer: Contains a chain of characters or pins that print an entire line
at one time. Line printers are very fast, but produce low‐quality print.
7.
thermal printer: An inexpensive printer that works by pushing heated pins
against heat‐sensitive paper. Thermal printers are widely used in calculators
and fax machines.
What
is a Printer? A printer is an electromechanical device which converts the text
and graphical documents from electronic form to the physical form. Generally
they are the external peripheral devices which are connected with the computers
or laptops through a cable or wirelessly to receive input data and print them
on the papers. A wide range of printers are available with a variety of
features ranging from printing black and white text documents to high quality
colored graphic images.
Quality
of printers is identified by its features like color quality, speed of
printing, resolution etc. Modern printers come with multipurpose functions i.e.
they are combination of printer, scanner, photocopier, fax, etc. To serve
different needs there are variety of printers available that works on different
types of technologies.
Types
of Printers Since the invention of the printing technology, a variety of
technologies have been employed in computer printers. Broadly printers are
categorized as impact and non impact printers. Impact printers are the type of
printers in which a key strikes the paper to make a letter. The examples of Impact
printers are Daisy wheel and Dot matrix printers. While non‐impact printers do
not operate by striking a head against a ribbon. Inkjet printers and laser
printers are the non‐impact printers. The most popular printers are described.
1. Daisy
Wheel Printers Daisy wheel printers print only characters and symbols and
cannot print graphics. They are generally slow with a printing speed of about
10 to 75 characters per second. By 1980 daisy wheel printers were the dominant
printers for quality printing but since the prices of laser and inkjet printers
have declined and quality of dot matrix printers has been improved, the daisy
wheel printers are now obsolete.
Working
of daisy wheel printers is very similar to typewriters. A circular printing
element (known as daisy wheel, shown in the below image) is the heart of these
printers that contains all text, numeric characters and symbols mould on each
petal on the circumference of the circle. The printing element rotates rapidly
with the help of a servo motor and pauses to allow the printing hammer to
strike the character against the paper.
2. Dot Matrix Printers It is a popular
computer printer that prints text and graphics on the paper by using tiny dots
to form the desired shapes. It uses an array of metal pins known as print head
to strike an inked printer ribbon and produce dots on the paper. These
combinations of dots form the desired shape on the paper. Generally they print
with a speed of 50 to 500 characters per second as per the quality of the printing
is desired. The quality of print is determined by the number of pins used
(varying from 9 to 24).
3. Inkjet
printers Inkjet printers are most popular printers for home and small scale
offices as they have a reasonable cost and a good quality of printing as well.
A typical inkjet printer can print with a resolution of more than 300 dpi and
some good quality inkjet printers are able to produce full colored hard copies
at 600 dpi. An inkjet printer is made of the following parts:
∙
Print
head – It is the heart of the printer which holds a series a nozzles which
sprays the ink drops over the paper.
∙
Ink
cartridge – It is the part that contains the ink for printing. Generally
monochrome (black & white) printers contain a black colored ink cartridges
and a color printer contains two cartridges – one with black ink and other with
primary colors (cyan, magenta and yellow).
Stepper
motor – It is housed in the printer to move the printer head and ink cartridges
back and forth across the paper. .
Stabilizer
bar – A stabilizer bar is used in printer to ensure the movement of print head
is précised and controlled over the paper. .
Belt
– A belt is used to attach the print head with the stepper motor.
.
Paper
Tray – It is the place where papers are placed to be printed.
.
Rollers
– Printers have a set of rollers that helps to pull paper from the tray for
printing purpose. . Paper tray stepper
motor‐ another stepper motor is used to rotate the rollers in order to
pull the paper in the printer. .
Control
Circuitry – The control circuit takes the input from the computer and by
decoding the input controls all mechanical operation of the printer.
Similar
to other printers, inkjet printers have a ‘print head’ as a key element. The
print head has many tiny nozzles also called as jets. When the printer receives
the command to print something, the print head starts spraying ink 33 over the
paper to form the characters and images. There are mainly two technologies that
are used to spray the ink by nozzles. These are:
∙
Thermal
Bubble – This technology is also known as bubble jet is used by various
manufacturers like Canon and Hewlett Packard. When printer receives commands to
print something, the current flows through a set of tiny resistors and they
produce heat. This heat in turn vaporizes the ink to create a bubble. As the
bubble expands, some of the ink moves out of the nozzle and gets deposited over
the paper. Then the bubble collapses and due to the vacuum it pulls more ink from
ink cartridge. There are generally 300 to 600 nozzles in a thermal printer head
which can spray the ink simultaneously.
∙
Piezoelectric
– In the piezoelectric technology, a piezo crystal is situated at the end of
the ink reservoir of a nozzle. When printer receives the command to print, an
electric charge is applied to the crystal which in turn starts vibrating and a
small amount of ink is pushed out of the nozzle. When the vibration stops the
nozzle pulls some more ink from the cartridge to replace the ink sprayed out.
This technology is patented by Seiko Epson Corporation.
An
inkjet printer can print 100 to several hundred papers depending on the nature
of the hard copy before the ink cartridge need to be replaced.
4. Laser
Printers Laser printers are the most popular printers that are mainly used for
large scale qualitative printing. They are among the most popularly used
fastest printers available in the market. A laser printer uses a slight
different approach for printing. It does not use ink like inkjet printers,
instead it uses a very fine powder known as ‘Toner’. Components of a laser
printer are shown in the following image:
The
control circuitry is the part of the printer that talks with the computer and
receives the printing data. A Raster Image Processor (RIP) converts the text
and images in to a virtual matrix of dots. The photo conducting drum which is
the key component of the laser printer has a special coating which receives the
positive and negative charge from a charging roller. A rapidly switching laser
beam scans the charged drum line by line. When the beam flashes on, it reverses
the charge of tiny spots on the drum, respecting to the dots that are to be
printed black. As soon the laser scans a line, a stepper motor moves the drum
in order to scan the next line by the laser.
