Chapter 5 Printer

8/9/2019 Chapter 5 Printer

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PREPARED BY : MOHD FADHIL BIN RAMLE


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` Is an output device that produces text and

graphics on a physical medium such as paper or

transparency film.


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` There are several types of printers:1. Impact printer.

2. Bubble-jet printers.

3. Laser printers (pages printers).4. Other printers.


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` The most basic printer.

` Use some form of impact and an inked ribbon to

make an imprint on the paper.

` Like a typewriter.` There are two major types of impact printers:

1. Daisy wheel

2. Dot matrix.


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` Contain a wheel (called daisy-wheel because it lookslike a daisy) with raised letters and symbols on eachpetal.

` When the printer needs to print a character, it sends asignal to the mechanism (printhead) that contains thewheel.

` The printhead rotates the daisy-wheel until the requiredcharacter is in replace.

` An electromechanical hammer (called solenoid) thenstrikes the back of the petal containin the character.

` The character pushes up against an inked ribbon thatultimately strikes the paper, makin the impression of therequested character.


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A daisy-wheel printer mechanism


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` Speed is rated by the number of characters persecond (cps) they can print.

` Disadvantages: The early printers could only print between two and

four characters per second.

The other advantage is that it makes a lot of noisewhen printing.`Advantages:

Can print on multipart forms (like carbonless receipts). Inexpensive compared to the price of laser printer at

the same vintage.

The print quality (LQ) is comparable to that of atypewriter because it uses a very similar technology.


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` These printers work in a manner similar to daisy-wheelprinters, but instead of a spinning, character-imprintedwheel, the printhead contains a row of pins (short, sturdystalks of hard wire).

` These pins are triggered in patterns that form letters andnumbers as the printhead move across the paper.

` The early dot-matrix printers used only nine pins to makethose patterns.

` As more pins crammed into the printhead (17-pin and

24-pin models were eventually developed), the qualityincreased (Near Letter Quality).


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Formation of images in a dot-matrix printer


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` The pins in the printhead are wrapped with coilsof wire to create a solenoid and are held in therest position by a combination of a small magnetand spring.

` To trigger a particular pin, the printer controllersends a signal to the printhead, which energizesthe wires around the appropriate print wire.

` This turns the print wire into an electromagnet,which repels the print pin, forcing it against the

ribbon and making a dot on the printer.


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` Disadvantages: Image quality (draft quality) is quite poor compared to the

quality produced with a daisy wheel.

`

Advantages: Print speed is faster (typically in the range of 36 to

72cps).

Can use multipart forms.


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`An advanced form of an older technology knownas inkjet printers.

` Both types of printers spray ink on the pages,but inkjet printers used a reservoir of ink, apump and an ink nozzle to accomplish this.

` Inkjet printer were messy, noisy an inefficientand bubble-jet printers work much moreefficiently and are much cheaper.

` In a bubble-jet printer, bubbles of ink aresprayed onto a page and form patterns that

resemble the items being printed.


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` The printer parts can be divided into the following

cateories. Printhead/ink catridge.

Head carriage, belt and stepper motor. Paper-feed mechanism.

Control, interface and power curcuitry.


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` Contains many small nozzles (usually 100-200)that spray the ink in small dots onto the page.

` Many times the printhead is part of the inkcatridge, which contain reservoir of ink and theprinthead in a removable package.

` Colour bubble-jet printers include multipleprinthead, one for each of the CMYK print inks.


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Chamber

` Inside the ink cartridge are small chambers.

`At the top of each chamber are a metal plate

and a tube leading to the ink supply.`At the bottom of each chamber is a small

pinhole used to spray ink on the page to form

character and images as patterns of dots

(similar to a dot-matrix printer but with higherresolution).


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` There are two methods of spraying the ink out of thecatridge.

1. First developed by Hewlett-Packard (HP): When a particular chamber needs to spray ink, an electrical

signal is sent to to the heating element, energizing it.

The elements heat up quickly, causing the ink to vaporize. Because of the expanding ink vapor, the ink is pushed out the

pinhole and forms a bubble.

As the vapor expands, the bubble eventually gets largeenough to break off into a droplet.

The rest of the ink is pulled back into the chamber by the

surface tension of theh ink. When another drop needs to be sprayed, the process begins

again.


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2. Second method developed by Epson: Use a piezoelectric element that flexes when

energized.

The outward flex pushes the ink from the nozzle; on

the return, it sucks more ink from the reservoir.


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` Printhead carriage : moves back and forth duringprinting.

` Contains the physical as electronic connections for the

printhead and the ink reservoir.

`

To keep the printhead carriage aligned and stable, thecarriage rests on a small metal stabilizer bar.

A printhead carriage in

a bubble-jet printer


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` Stepper motor and belt make the printheadcarriage move.

` Stepper motor: Move in the same very small increment each time it is

activated. Move the printhead. Called carriage motororcarriage stepper motor.

` Belt: Placed around two small wheels or pulleys and

attached to the printhead. Called carriage belt, and driven by the carriage motor.


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A carriage

stepper

motor


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Stabilizer bar, carriage belt, and pulley in a bubble jet printer


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Pickup Rollers.` Several rubber rollers with a slightly flat spot; they rub

against the paper as they rotate, and feed the paper intothe printer.

Separator pads.` Keep the rest of the paper in place.

PaperTray` Holds the paper until it is fed into the printer.

Paper Feeder` The paper is placed vertically into paper feeder at the

back of the printer; it uses gravity with combination withfeed rollers and separator pads, to get the paper into theprinter.


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Bubble-jet pickup rollers


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Bubble-jet seperator pads


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A paper tray on a bubble jet printer


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Paper-Feed Sensor.

` Tell the printer when it is out of paper, as well as when a

paper jam occurred during the paper feed process.

Paper-Feed Sensor


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Printercontrolcircuit.` Contains the circuitry to run the stepper motors.` Monitoring the health of the printer and reporting that

information back to the PC

Interface Circuit (commonlycalled a port).` Make a physical connection to whatever signal is coming

from the computer (parallel, serial, SCSI, network,infrared and so on).

` Connect the interface to control circuit.` Convert the signals from the computer into the

datastream that the printer uses.

PowerCircuits.` Convert 110V or 220V into 12V and 5V.


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` Laser printers and inkjet printers are referred to

aspage printers because they received their

printer job instructions one page at a time.

` Two major types of page printers: Use the electrophotographic (EP) print process.

Use the light-emitting diode (LED) print process.


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` Scientist at Xerox developed the

electrophotographic (EP) process in 1971.

` Xerox, Hewlett-Packard and Canon were pioneer

in laser printer technology.` This technology uses a combination of static

electric charges, laser light and a black powdery

substance called toner.


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Basic Components` Contains eight standard assemblies:

Toner cartridge Laser scanner

High-voltage power supply DC power supply Paper transport assembly Transfer corona. Fusing assembly Controller circuitry Ozone filter.


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Toner Cartridge` Hold the toner.` Toner = black carbon substance + polyster resins (to

make it flow better) + iron oxide particles (to make thetoner sensitive to electrical charges).

`

This two components make the toner capable of beingattracted to the photosensitive drum and of melting intothe paper.

` Developercarries the toner until it is used by the EPprocess.

` PrintDrum is coated with photosensitive material that

can hold static charge when not exposed to light.` Cleaning blade continuously scrapes the used toner off

the photosensitive drum to keep it clean.


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An EP toner cartridge


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LaserScanning Assembly

` Shine particular area of the photosensitive drum.

` The drum will discharge but only in that area.

`

The laser light is damaging to human eyes,therefore the laser is kept in an enclosure and willoperate when the laser printers cover is closed.


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The EP laser assembly (side view and simplified top view)


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High-voltage PowerSupply (HVPS)

` EP process requires high-voltage electricity.

` HVPS provide the high voltages during the EP

process.` Converts house AC current (120V and 60Hz)

into higher voltages that the printer can use.

` This high voltage is used to energize both the

charging corona and transfer corona.


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DC PowerSupply (DCPS)

` The high voltage cannot power the other

components in the printer (the logic circuit and

motors).` Convert house AC current into +5VDC, -5VDC

(for logic circuit) and +24VDC (for paper

transport motor).


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PaperTransport Assembly

` Moving the paper through the printer.

` Feed roller: D-shaped roller that rotates again

the paper and pushes one sheet into the printer.` Registration roller: there are two registration

roller that synchronize the paper movement withthe image-formation process.


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Paper transport rollers


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TransferCorona Assembly` Transfer corona is given a high-voltage charge

which is transferred to the paper which pulls thetoner from the photosensitive drum.

` Staticeliminator strip: drain away the chargeimparted to the paper by corona. Paper wouldstick to the EP cartridge and jam the paper if thecharge didnt away.

` Two type of transfer corona assemblies: Contains a transfercorona wire Contains a transfercorona roller


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The transfer corona assembly


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Fusing Assembly` Use two rollers that apply pressure and heat to

fuse the plastic toner particles to the paper.` Made up of three parts: a halogen heating lamp,

a Teflon-coated aluminum fusing roller andrubberized pressure roller.

` Halogen lamp heat the fusing roller to between165oC-180oC.

`As paper pass through the two rolles, thepresure roller pushes the paper against the

fusing roller which melts the toner into the paper.


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The f ser


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PrinterControllerCircuit

` Converts signals from the computer into signal for

various assemblies in the laser printer using

process called known as resterizing.` Formats the information into pages worth of line-

by-line commands for the laser printer.


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Ozone filter

` Ozone is a chemically reactive gas that createdby the high-voltage coronas.

` Ozone can reduce the life of laser printerscomponent.

` Ozone filter used to remove ozone gas.

` But, many newer laser printer dont have ozonefilter because they done use transfer corona

wires but instead use transfer corona roller.


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Electrophotographic (EP) Print Process.

1. Cleaning

2. Charging

3. Writing4. Developing

5. Transferring

6. Fusing


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STEP 1 : Cleaning

` Rubber blade inside EP cartridge scrapes any

toner left on the drum.

` Fluorescent lamp discharge any remainingcharge on the photosensitive drum.


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The cleaning step of the EP process


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STEP 2 : Charging

` special wire or roller (called charging corona)

within EP toner cartridge gets high voltage to

apply strong, uniform negative charge (around -600VDC) to the surface of the photosensitive

drum.


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The charging step of the EP process


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STEP 3 : Writing

` Laser is turn on and scans the drum from side to side.

` The laser flashing on and off according to the bits of

information.

` Wherever the laser beam touches, the photosensitive

drums charge is severely reduced from -600VDC to a

slight negative charge (-100VDC).

` As the drum rotates, a pattern of exposed area is

formed, representing the image to be printed.


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The writing step of the EP process


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STEP 4 : Developing

` Surface of drum holds an electrical

representation of image to be printed.


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The developing step of the EP process


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STEP 5 : Transferring` The controller sends a signal to the charging corona wire

or roller and tells it to turn on.` The corona wire/roller acquires a strong positive charge

(+600VDC) and apply that charge to the paper.` The paper thus charged, pulls the toner from the

photosensitive drum at the line of contact between theroller and paper, because the paper and have positivecharge.

` Once the registration roller move the paper past thecorona wire, the static-eliminator strip removes allcharge from that linbe of the paper.


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The tr sf erri step f the pr cess


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STEP 6 : Fusing

` The toner image is made permanent.

`As the paper passes through the fuser, the

350oF fuser roller melts the polyester resin ofthe toner and rubberized pressure roller presses

it permanently into the paper.


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The f si step f the pr cess


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The EP print process


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` Primarily developed by Okidata and Panasonic.

` There are two main differences between a LED

page printer and a laser printer: toner cartridges

and print process.


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LED Page PrinterTonerCartridges

` Photosensitive drum/toner and toner separate and

replaceable item.

`

When replacing the photosensitive drum, youswing the photosensitive drum/toner cartridge out

of the printer first.

` Filling the toner hopper is fairly easy.


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LED Page Printer Process` Same process as a laser printer.` Use a row of small light-emitting diodes held very close to the

photosensitive drum to expose it.` Each LED is about the same size as the diameter of the laser beam

used in laser printers.

` Basically same as EP process printers except that in the writing step, they used LED instead of a laser.` Benefit:

Cheaper Smaller not dangerous to eye

` Disadvantages over laser printer Resolution 800dpi Messier (because its slight static charge, toner isnt easy to removefrom

surfaces).


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` Printer Interface: collection of hardware and

software that allows the printer to communicate

with computer. Hardware-port

Interface software-correct software for the platform being

used.


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Communication Types

` Ports used in getting the printed information

from the computer to the printer.

` Eight major type: serial, parallel, Universal SerialBus (USB), network, infrared, SCSI, IEEE 1394

and wireless.


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SERIAL

` Send data one bit at a time.

PARALLEL

` Receiving data 8 bit at a time over eight separate wires.` Faster than serial

` Parallel cable consists of DB-25 connector that connectsto the computer and a male 36-pin Centronics connector.

` Cable long less than 10 feetlong.

` Should be IEEE 1284 compliant.


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Universal Serial Bus (USB)` Most popular type of printer interface.` Higher transfer rate than either serial or parallel.` Automatically recognizes new devices.

NETWORK` Some newer printers (laser and LED printers) have

special interface that allows them to be hooked directlyto a network.

` This printers have a network interface card and ROM

based software that allows them to communicate withnetworks, servers and workstations.


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INFRARED` Many laser printers (and some computer) come with

infrared transmitter/receivers so that they cancommunicate with the infrared ports on many handhelds.

` The infrared interfaces are enabled by default on mostcomputer, handhelds and printers.

SCSI` Only few types of printers use SCSI interfaces to the PC:

laser printers, dye-sublimation printers or typesetters` Benefit:

There could be more than one device on a single SCSIconnection through daisy chaining.

Fairly simple to implement. Had large throughput compared to other interfaces of time.


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IEEE 1394 FIREWIRE` .supports devices with a maximum throughput of

800MBps and is capable of speeds up to3.2Gbps.

WIRELESS` Some printers have bulilt-in 802.11 interfaces or

are hooked to 802.11 bridges with their built-innetwork cards.

`Another wireless technology is bluetooth withmaximum range is 100 meters and most devicework within 10meters.


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` Need regular cleaning .` The condition of both the platen and the print

head direcly impacts print quality.` If too much dried ink and print fiber gets jammed

into the print head, the pins might not be ejectedby the springs.` Never send print job onto dot matrix printer

when theres no paper installed.` Both the print head and the platen need to be in

proper alignment as well, if not, individualcharacters will shade from light to dark.


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` Printer errors will generally fall under one of four

categories:1. Communication errors.

2. Processing errors

3. Paper transport errors

4. Imaging errors


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1. Communication error Occur when computer cant find the printer. First thing to check is cable Bypass the driver by opening a command prompt

and copying an ASCII tect file directly to LPT1.x As example:

i. open notepad, type out a few characters and save the file asC:\document\test.txt.

ii. At command prompt, type copy C:\document\test.txt. LPT1and see if the printer fires up and spits out the document.

If it does, you have physical connectivity to theprinter. The problem is in the configuration.

Reinstall the driver and use the correct one thistime.


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3. Paper transport error Cause by paper jams or the paper not being picked

up out of the delivery tray.

Paper jam cause by rollers are smooth and medium

not supported (too light or too heavy) by printer.


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Chapter 5 Printer

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