Printer

S.N.College , Gadhinglaj

Printer Basics
• Printer is one of the most important peripheral component of the
computer.
• There are different types of printers classified basically on the
printing technology.
• The printers are evaluated on the basis of the following
factors:
– Printer Resolution:-It is measured in dots per inch(dpi). It
indicates the number of vertical and horizontal dots that can be
printed. Higher the resolution better is the quality.


– Speed : It is the number of pages printed per minute.
– Graphics and printer-language support: It should support one or more
printer languages such as Adobe PostScript and Hewlett Packard’s
LaserJet Printer Control Language(PCL).
– Paper Capacity: The number of pages that can be accommodated in
the paper tray. The different sizes of pages that can be printed by the
printer.


Printer Basics
– Duty Cycle: It is the number of sheets of paper the printer is rated to
print per month.
– Printer memory: It is used to store complex graphics and full-color
images require larger amounts of memory.
– Cost of Paper: It indicates the cost of any special paper.
– Cost of Consumables: It indicates the total cost per page for
printing.


Classification Of Printers
•In general Printers can be classified in two broad categories

– IMPACT TYPE PRINTERS
In this type, physical force is applied to get an impression of the
character.
E.g.s DAISY-WHEEL printers, DOT-MATRIX printers, LINE printers

– NON-IMPACT TYPE PRINTERS
In this type, physical force is NOT applied to get an impression of
character; instead either the IMAGE is transferred to paper
Electrostaticallyor ink is sprayed on to paper to form the
character.
E.g.s INK-JET printers, LASER printers


Daisy-Wheel Printers
• Daisy-Wheel is a small plastic
wheel with many spokes, at the

ends of which Raised Image of
Characters are provided.
• Solenoid driven hammer strikes the
daisy-wheel as the appropriate

character is in front of the paper
which causes the spoke containing
the desired character to press
against ribbon, thus printing it on
the paper.


Dot Matrix Printer (DMP)


• Dot-Matrix printers strike the page with small rods (called
needles) that protrude from the print head.
• Most expensive part of a dot-matrix printer that dies is the print
head.
• Almost, all dot-matrix printers these days have a thermistorthat
detects when the print head is getting too hot and shuts the printer
down until it cools off.


• DMPscan be characterized by following 5 parameters.
–No of pins in print head.
–Characters per second (CPS)
–Characters per inch (CPI)
–Width of printer (in columns)
–Interface used [parallel / serial]


No of pins in print head.
• 9 pins
• 24 pins

There are two modes of printing.

• Draft
• NLQ (Near letter quality).


Characters per second (CPS)
• This parameter indicates how many characters can be printed
in one second.
• Example For FX 1000
–In DRAFT -CPS = 240 char/s
–In NLQ -CPS = 40 char/s
• The CPS is always greater for draft mode than that for NLQ.


Characters per inch (CPI)
• Indicates how many characters can be printed in an inch
length of a printable row.
• Commonly used CPI’s are -10 cpi, 12 cpior 15 cpi.
• Normally, the 15 cpimode or 17 cpiis called as condensed mode.
• In new printers 20 cpiis also possible.


Width of the printer
• Indicates the size of printer.
• The two standard sizes are 80 column & 132 column.
• Mean’s that the printer can print 80/132 different characters in one
printable line (row).
• This parameter also indicates the size of stationery that will be
used with that printer.


Interface used
• Two types of interfaces used to communicate with computer.
–Parallel
–Serial
• For parallel interface, we use a standard 36 pin centronics
interface.
• This interface has
–25 pin D type female connector to the computer side
–36 pin Amphenoltype connector to printer side.


How Dot -Matrix Printer Works

•Your PC sends a series of hexadecimal ASCII codes that

represent

–Characters

–Punctuation marks

–Printer movements such as tabs, carriage returns, line feeds,

and form feeds

–This control the position of the print head in relation to the

paper.


• The ASCII codes are stored in a buffer, which is a special
section of the printer's random access memory (RAM).
• It usually takes longer time for a dot-matrix printer to print
characters than it takes a PC and software to send those
characters to the printer
• The buffer helps free up the PC to perform other functions
during printing.
• The internal buffer of a dot-matrix printer generally has only a
7k to 8k capacity.


• When the buffer gets full, the printer sends an XOFF control code to
the computer to tell it to suspend its stream of data.
• When the buffer frees up space by sending some of the
characters to its processor
• The printer sends an XON code to the PC, which resumes sending
data.


• Among other codes are commands that tell the printer to use a
certain font's bitmap table, which is contained in the printer's
read-only memory chips.
• That table tells the printer the pattern of dots that it should use to
create the characters represented by the ASCII codes.
• The printer's processor takes information provided by the
bitmap table for an entire line of type


• It calculates the most efficient path for the print head to
travel. (Some lines may actually be printed from right to left.)
• The processor sends the signals that fire the pins in the print head
• It also controls the movements of the print head and platen.


• Electrical signals from the processor are amplified and travel to
certain of the circuits that lead to the print head.
• The print head contains 9 or 24 wires, called printing pins, that
are aligned in one or two straight lines.
• One end of each of the pins is matched to an individual
solenoid, or electromagnet.


How Dot -Matrix Printer Works
• The current from the processor activates the solenoid, which
creates a magnetic field that repels a magnet on the end of the
pin, causing the pin to move toward the paper.
• The moving pin strikes a ribbon that is coated with ink.
• The force of the impact transfers ink to the paper on the
other side of the ribbon.


How Dot-Matrix Printer Works
•After the pin fires, a spring pulls it back to its original

• position.
The print head continues firing different combinations of
print wires
• Print head moves across the page so that all characters are
made up of various vertical dot patterns.
• Some printers improve print quality or create boldface by
moving the print head through a second pass over the same
line of type.


Major Parts of a Dot Matrix Printer (DMP)
• In general any DMP can be divided into 4 major parts.
• Mechanical assembly
• Logic Card
• Power Card
• Front Panel


The Mechanical Assembly

The mechanical assembly can be divided into following parts:

•Print head : with cable or without cable

•Carriage & carriage assembly

•Carriage motor, timing belt/carriage wire.

•Sensors Home position & Paper empty

•Platen, line feed gear assembly & line feed motor.

•Levers


The Mechanical Assembly
• Paper thickness adjustment,
• Friction
• Plunger (automatic paper loading)
• Ribbon & ribbon gear assembly
• Tractor assembly


The Print Head


The Print Head
• Two types of print heads
• With cable
• Without cable.
• With cable
• The head cable is directly soldered to the print head
• If the cable becomes faulty you have to throw the complete head.
• Hence, it is not preferable.
• e.g. TVSE series except LSP100


The Print Head
• Without cable
• The head cable is connected to head through a connector.
• If the cable is gone faulty, then it can be easily replaced.
• Hence, it is preferred.
• eg. EPSON series except FX105 MX80


Carriage & carriage assembly
• This provides the movement for the print head.
• It is having a base for head & two rails.
• Over these rails the base or ‘carriage’ moves horizontally from
left to right & back.
• The base has bearings wherever it comes into contact with the
rails.


Carriage motor, timing belt/carriage wire
• Carriage motor is basically a
stepper motor.

• Carriage motor provides the
actual force to move the carriage.
• This force is converted into the actual motion of carriage using
either the timing belt or the carriage wire.


Carriage motor, timing belt/carriage wire
• FX1000 -Timing belt
• EX1000 -Carriage wire

• The tension of the belt/wire

is an important

consideration while

troubleshooting.


Sensors
• Home position sensor
• The print-head is able to move freely
• The controlling BIOS of printer must know its exact position.
• The leftmost position is taken as ‘reference or home position’.
• This must be detected.
• For detecting it, the home position sensor is used which is an
normal photo detector circuit.


Sensors
• The carriage has a vertical slit below it.
• Whenever, it reaches to left most position, the slit blocks the
photo emission, thus giving a pulse.
• Paper empty sensor
• The printer should print only when there is paper in front of the
print -head.
• To detect the status of paper a simple mechanical micro –switch
is used.


Platen, line feed motor and gears
• Whenever one line is printed, the paper should be moved by
some distance so that the next line will get printed in a
intelligible manner.
• This is performed using platen & line feed motor & gear
assembly.
• Platen is a hard rubberized rod that provides striking surface for
the print-head pins.


Platen, line feed motor and gears
• Line feed motor is also a

stepper motor & its motion is

given through line feed gear assembly.


Levers

Paper thickness adjust lever :

•This lever is used to adjust the gap between the platen and the

print head..

•This lever virtually moves the head back & forth in horizontal

plane very slightly.


Levers

Friction lever :

•Used when not using continuous stationery

•Used if you are using cut-sheet papers

•Friction lever move paper with platen.


Levers
• This friction lever adjusts the friction rollers so that in friction
mode the pressure rollers are very tightly coupled to the
platen.
• In between them the cut-sheet paper is present.
• As a result, the paper will move with platen movement.


Ribbon & ribbon gear assembly
• Ribbon provides the ink required for printing.
• If the same area of ribbon is used for printing, the print quality will
go on fading.
• For this, the ribbon is always moved in one direction only, i.e.from
one side it goes in the box and for other side it comes out.


Ribbon & ribbon gear assembly
• Inside the box it is re-inked.
• To move the ribbon in only one direction while the head is
moving in both direction, ribbon gear assembly is used.
• Tractor assembly :
• This is used only with continuous stationery which has
perforation holes at the side.


• It is of two types.

• Push
•Pull

Note •Whenever tractor assembly is being used never put paper in friction mode.


Logic Card
• It is the main printed circuit board which controls the working
of the printer.
• It co-ordinates between the different actions performed by the
printer.


Power Supply Card
• This card supplies the power required by the printer for it's
operations.
• It is responsible for converting the line a.c. voltage into
appropriate d.c. voltages required by the different parts of the
printer.


Front Panel
• Front panel of DMP'svaries from model to model however most of
the printers will have the following LED's and buttons which have
been displayed along with their functions.


Line Printers
• Printers are often used for printing large database reports whose
speed is tremendous e.g 1500 lines/minute.
• Different technologies exist for line printers wherein some low-end
line printers contain print head for each character positionon a line
and a whole line is printed at a time.
• Some printers use band or chain technology wherein the band or
chain of characters runs across full width of paper and is rotated
along the length of line.


Ink-Jet Printers
• Inkjet printers work by directing tiny droplets of ink onto
paper.
• Print head contains a series of Nozzles and are arranged in
vertical lines and these nozzles produce fine drops of ink and
form a character.
•Resolution (print quality) depends
upon the number of
nozzles. (eg., 300 dpi).

• Two types of inkjet printers
–Thermal
–Piezo


Thermal Inkjets
• Used by manufacturers, such as Canon and Hewlett Packard, and
this method is commonly referred to as bubble jet.
• They heat the ink in the cartridge (to about 400 degrees
Fahrenheit), causing vapourbubbles in the cartridge that rise
to the top and force the ink out
through the nozzle.

• A typical bubble jet print head has
300 or 600 tiny nozzles, and all
of them can fire a droplet
simultaneously.


Piezo Printing
• Piezoprinting uses an electric charge instead of heat which is
patented by Epson.
• It charges piezoelectric crystals in the nozzles, which change
their shape as a result of the electric current, forcing the ink out
through the nozzles.
• When the crystal vibrates inward, it forces a tiny amount of ink
out of the nozzle and when it vibrates out, it pulls some more ink
into the reservoir to replace the ink sprayed out.


Parts of a typical inkjet printer
• Print head assembly

• Print head
• The core of an inkjet printer
• The print head contains a series of nozzles that are used
to spray drops of ink.


Ink cartridges
• Ink cartridges come in various combinations such as
•Separate black and color cartridges
•Color and black in a single cartridge
•Cartridge for each ink color.
• The cartridges of some inkjet printers include the print
head itself.


Print head stepper motor
• A stepper motor moves the print head assembly (print

• head and ink cartridges) back and forth across the paper. Some
printers have another stepper motor to park the print
head assembly when the printer is not in use.
• Parking means that the print head assembly is restricted from
accidentally moving.



A picture showing Print Head


•Belt
• A belt is used to attach the print head assembly to the
stepper motor.
• Stabilizer bar
• The print head assembly uses a stabilizer bar to ensure
that movement is precise and controlled.


Paper feed assembly
•Paper tray/feeder

• Most inkjet printers have a tray that you load the paper into.
• Some printers dispense with the standard tray for a
feeder instead.
• The feeder typically snaps open at an angle on the back of
the printer, allowing you to place paper in it.
• Feeders generally do not hold as much paper as a
traditional paper tray.


Rollers
•A set of rollers pull the paper in from the tray or feeder

and advance the paper when the print head assembly is

ready for another pass.


Rollers
• Paper feed stepper motor
• This stepper motor powers the rollers to move the
paper in the exact increment needed to ensure a
continuous image is printed.
• Power supply
• While earlier printers often had an external transformer
• Most printers use a standard power supply that is
incorporated into the printer itself.


Rollers
•The mechanical operation of the printer is controlled by a

small circuit board containing a microprocessor and

memory.


Interface port(s)
•The most popular way of connecting a printer to a

computer is through the parallel port

• A large number of newer printers use a Universal Serial
Bus (USB) port instead.
• A few printers connect using a serial port or small
computer system interface (SCSI) port.

parallel port


Working of Inkjet Printers
• The software application you are using sends the data to

• be printed to the printer driver.
The driver translates the data into a format that the printer
can understand
• Checks to see that the printer is online and available to
print.


• The data is sent by the driver from the computer to the
printer via the connection interface (parallel, USB, etc.)
• The printer receives the data from the computer.
• It stores a certain amount of data in a buffer.
• The buffer can range from 512 KB random access memory
(RAM) to 16 MB RAM, depending on the model.


•Buffers are useful because they allow the computer to

finish with the printing process quickly, instead of
having to wait for the actual page to print.
• A large buffer can hold a complex document or several basic
documents.
• If the printer has been idle for a period of time, it will
normally go through a short clean cycle to make sure
that the print head(s) are clean.


•Once the clean cycle is complete, the printer is ready to

• begin printing.
The control circuitry activates the paper feed stepper
motor.
• This engages the rollers, which feed a sheet of paper
from the paper tray/feeder into the printer.
• A small trigger mechanism in the tray/feeder is
depressed when there is paper in the tray or feeder.


• If the trigger is not depressed, the printer lights up the
"Out of Paper" LED and sends an alert to the computer.
• The paper is fed into the printer and positioned at the
start of the page
• The print head stepper motor uses the belt to move the print
head assembly across the page.


• The motor pauses for the fraction of a second each time that
the print head sprays dots of ink on the page
• It then moves a tiny bit before stopping again.
• This stepping happens so fast that it seems like a
continuous motion.
• Multiple dots are made at each stop.


• It sprays the CMYK colors in precise amounts to make any
other color imaginable.
• At the end of each complete pass, the paper feed
stepper motor advances the paper a fraction of an inch.
• Depending on the inkjet model, the print head is reset to the
beginning side of the page
• In most cases, Print head simply reverses direction and
begins to move back across the page as it prints.


• This process continues until the page is printed.
• The time it takes to print a page can vary widely from
printer to printer.
• It will also vary based on the complexity of the page
and size of any images on the page.


Example

• A printer may be able to print 16 pages per minute (PPM) of black
text but take a couple of minutes to print one, full-color,
page-sized image.
• Once the printing is complete, the print head is parked.
• The paper feed stepper motor spins the rollers to finish
pushing the completed page into the output tray.
• Most printers today use inks that are very fast-drying, so that
you can immediately pick up the sheet without smudging it.


Inkjet cartridges
• A typical color ink cartridge for a
Hewlett Packard DeskJet printer.

• This particular cartridge has cyan,

magenta and yellow inks in

separate reservoirs in the same

cartridge


Inkjet cartridges
• Refilling Cartridges
• Because of the expense of inkjet cartridges, a huge
business has grown around the idea of refilling them.
• Few things to be aware
• Make sure the refill kit is for your printer model.
• Different printers use different technologies for putting the
ink on the paper.


Inkjet cartridges
• If the wrong type of ink is used, it can degrade the output or
possibly damage the printer.
• While some commercial inkjets use oil-based inks, virtually all
desktop inkjets for home or office use have water-based ink.
• The exact ink composition varies greatly between
manufacturers.


Laser Printers
• They are Non-Impact printers which is used to print large volumes.
• Their basic principle of operation is the static electricity andis exactly
similar to a normal photocopying machine.
• Commonly available lower priced units have a resolution of 1200 dots
per inch with print speeds in the range of 17-19 pages per minute for
text and 6

to 7 pages per minute for graphics.
• Two types of print engines:
•Write-white engine

•Write-black engine


Parts of Printer
• It basically comprises of mechanical and electronic
components.
• To reduce maintenance costs, many of the laser printer parts,
including those that suffer the most wear and tear, have been
incorporated into the toner cartridge.
– Photosensitive Drum
• It is an aluminiumcylinder coated with particles of photosensitive
compounds.
• When light hits these particles, whatever electrical charge theymay have
had drains out through the grounded cylinder.


Parts of Printer
– Erase Lamp
Erase lamp exposes the entire surface of the photosensitive drumto
light, making the photosensitive coating conductive.
– Primary Corona
• When charged with an extremely high voltage, an electric field (or corona)
forms, enabling voltage to pass to the drum and charge the
photosensitive particles on its surface.
• Primary grid regulates the transfer of voltage, ensuring that the
surface of the drum receives a uniform negative voltage of between ~600
and ~1,000 volts.


Parts of Printer
• Laser
•Laser acts as the writing mechanism of the printer.
• Any particle on the drum struck by the laser becomes
conductive, enabling its charge to be drained away into the
grounded core of the drum.
•Toner
• Toner in a laser printer is a fine powder make up of
plastic particles bonded to iron particles.
• Toner cylinder charges the toner with a negative charge of
between ~200 and ~500 volts.


Parts of Printer
• Transfer - Corona Transfer corona applies a positive charge to
the paper, drawing the negatively charged toner particles to
the paper.
• Fuser- Toner must be permanently attached to the paper to
make the image permanent and for this there are two rollers,
a pressure roller and a heated roller, are used to fuse the
toner to the paper.


Working
• Printing process takes six steps in this
order
1.Clean4.Develop

2. Charge 5. Transfer
3. Write 6. Fuse
– Clean the Drum
• Before printing each new page, drum must be returned to a clean,fresh
condition and all residual toner left over from printing the
previous page must be removed.
• One or more erase lamps bombard the surface of the drum with the
appropriate wavelengths of light, causing the surface particles to
completely discharge into the grounded drum.


Working
– Charge the Drum
• Using the primary corona wire, a uniform negative charge is applied to the
entire surface of the drum (usually between ~600 and ~1,000
volts).
– Write and Develop the Image
• Every particle on the drum hit by the laser will release most ofits negative
charge into the drum and those particles with a lesser
negative charge will be positively charged relative to the toner
particles and will attract them, creating a developed image.
– Transfer the Image
• Using the transfer corona, paper is charged with a positive charge, and
negatively charged toner particles leap from the drum to the
paper


Working


Working
– Fuse the Image

•Toner particles are mostly

composed of plastic, so they can be melted to the page and thus two rollers,

a heated roller coated in a non-stick material and a pressure roller, melt the
toner to the paper, permanently affixing it which prevent toner particles from
falling off the page.


Troubleshooting Dot Matrix Printer
Symptom Possible Cause -:

Printer does not function at No power is getting to printer.
all. Fuse is blown.
Device does not print Printer is not online.
although power is on. Printer is out of paper.
Printer cable is disconnected.
Printer won't go online. Printer is out of paper. (Check
connections.)
Paper slips around platen. Paper is not being gripped properly.
(Adjust paper-feed selector for size
and type of paper.)


Symptom Possible Cause
Head moves but does Ribbon is not installed properly or
not print is out of ink.
Head tears paper as it Pins are not operating properly.
moves (Check pins; if any are frozen, the
head needs to be replaced.)
Paper bunches up There is no reverse tension on
around platen. paper.
Paper has "dimples." Paper is misaligned or the tractor
feed wheels are not locked in
place.
Paper/Error indicator There is an overload condition.
flashes continuously.


Printout is double-spaced Printer configuration switch is
or there is no spacing improperly set.
between lines.
Printer cannot print ASCII Printer configuration switch is
characters above code 127 improperly set.

Print mode cannot be Printer configuration switch is
changed improperly set.


• Troubleshooting Ink Jet Printer
–The first step when a printer is not working is to rule out whether
the problem lies with printer or computer.
–Check the tray for out of paper or paper jam.
–Print a test page by holding a specified combination of keys on
the printer.
–If the page prints properly, then the problem is with the printer
cable or the computer or the network.


The following table lists some of the symptoms and possible causes.

Power is on but device does not Printer is not online.
print. Printer is out of paper.
Printer won't go online after user Cartridge is installed incorrectly.
has replaced ink cartridge. Printer cable is disconnected.

Print head does not print. Ink reservoirs are empty
Paper does not advance Paper-handling hardware is jammed

Printer is plugged in, but all Check the drive mechanisms and motors for
indicator lights are off and the printer signs of binding. Fuse is blown.
appears to be dead.


Page is completely black. Primary corona, laser scanning module,
or main central board has failed.

Random black spots or streaks Drum was improperly cleaned; residual
appear on page. particles remain on drum.
Marks appear on every page. Drum is damaged and must be replaced.

Printing is too light. Toner is low.
Memory overflow error. Not enough RAM—printing resolution too
high
Characters are incomplete Print density is incorrect


Mass of melted plastic is spit out. Wrong transparency material is
used.
Pages are creased. Paper type is incorrect.
Characters are warped, over- There is a problem with the paper
printed, or poorly formed. or other media or with the
hardware.
After clearing a paper jam from the Printer has not reset
tray, printer still indicates a paper
jam.

Paper continues to jam. Problem with the pickup area,
turning area, and registration area


Troubleshooting Laser Printer Problems

The following table lists a few problems that can be
encountered with laser printing and their possible causes.
Ghost images appear at regular Photosensitive drum is not fully
intervals on the printed page discharged.
Light ghosting appears on pages. The drum could not be properly
charged for the image
Dark ghosting appears on pages Drum is damaged.

Design & Published by :
S.N.College ,Gadhinglaj ,
Prof- N.S.Kodoli .

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