Laser Printer2

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1. INTRODUCTION

A laser printer is a common type of computer printer that

rapidly produces high quality text and graphics onplain paper.

As with digitalphotocopiers andmultifunction printers (MFPs),laser printers employ a xerographicprinting process, but differ

from analog photocopiers in that the image is produced by the

direct scanning of a laser beam across the printer's

photoreceptor.

A laser printer is a popular type of personal computerprinter that uses a non-impact (keys don't

strike the paper), photocopier technology. When a document is sent to the printer, a laser beam

"draws" the document on a selenium-coated drum using electrical charges. After the drum is

charged, it is rolled in toner, a dry powder type of ink. The toner adheres to the charged image on

the drum. The toner is transferred onto a piece of paper and fused to the paper with heat and

pressure. After the document is printed, the electrical charge is removed from the drum and the

excess toner is collected. Most laser printers print only in monochrome. A color laser printer is

up to 10 times more expensive than a monochrome laser printer.

IBM introduced the first laser printer in 1975 for use with its mainframe computers. In 1984,

Hewlett-Packard revolutionized laser-printing technology with its first LaserJet, a compact, fast,

and reliable printer that personal computer users could afford. Since then, laser printers have

decreased further in price and increased in quality. Hewlett Packard continues to be the leading

manufacturer with competitors including Lexmark, Okidata, and Xerox.

The laser printer is different from an inkjet printer in a number of ways. The toner or ink in a

laser printer is dry. In an inkjet, it is wet. Over time, an inkjet printer is about ten times more

expensive to operate than a laser printer because ink needs replenishing more frequently. The

printed paper from an inkjet printer will smear if wet, but a laser-printed document will not. Both

types of printer operate quietly and allow fonts to be added by usingfont cartridges or installing

soft fonts. If your printing needs are minimal, an inkjet printer is sufficient. But if your printing

volume is high, consider buying a laser printer.
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2. OVERVIEW

A laser beam projects an image of the page to be printed onto an electrically charged rotating

drum coated with selenium or, more common in modern printers, organic photoconductors.

Photoconductivity allows charge to leak away from the areas exposed to light. Dry ink (toner)

particles are then electrostaticallypicked up by the drum's charged areas, which have not been

exposed to light. The drum then prints the image onto paper by direct contact and heat, which

fuses the ink to the paper.

Unlike impact printers, laser printer speed can vary widely, and depends on many factors,

including the graphic intensity of the job being processed. The fastest models can print over 200

monochrome pages per minute (12,000 pages per hour). The fastest color laser printers can print

over 100 pages per minute (6000 pages per hour). Very high-speed laser printers are used for

mass mailings of personalized documents, such as credit card or utility bills, and are competing

withlithography in some commercial applications.

The cost of this technology depends on a combination of factors, including the cost of paper,

toner, and infrequent drum replacement, as well as the replacement of other consumables such as

the fuser assembly and transfer assembly. Often printers with soft plastic drums can have a very

high cost of ownership that does not become apparent until the drum requires replacement.

Aduplexing printer (one that prints on both sides of the paper) can halve paper costs and reduce

filing volumes. Formerly only available on high-end printers, duplexers are now common on

mid-range office printers, though not all printers can accommodate a duplexing unit. Duplexing

can also give a slower page-printing speed, because of the longer paper path.

In comparison with the laser printer, mostinkjet printers anddot-matrix printers simply take an

incoming stream of data and directly imprint it in a slow lurching process that may include

pauses as the printer waits for more data. A laser printer is unable to work this way because such

a large amount of data needs to output to the printing device in a rapid, continuous process. The

printer cannot stop the mechanism precisely enough to wait until more data arrives, without

creating a visible gap or misalignment of the dots on the printed page.
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3. HISTORY

The laser printer was invented at Xerox in 1969 by researcherGary Starkweather,who had an

improved printer working by 1971 and incorporated into a fully functional networked printer

system by about a year later. The prototype was built by modifying an existing xerographic

copier.Starkweather disabled the imaging system and created a spinning drum with 8 mirrored

sides, with a laser focused on the drum. Light from the laser would bounce off the spinning

drum, sweeping across the page as it traveled through the copier. The hardware was completed in

just a week or two, but the computer interface and software took almost 3 months to complete.

The first commercial implementation of a laser printer was theIBMmodel 3800 in 1975, used

for high-volume printing of documents such as invoices and mailing labels. It is often cited as

"taking up a whole room," implying that it was a primitive version of the later familiar device

used with a personal computer.While large, it was designed for an entirely different purpose.

Many 3800s are still in use. The first laser printer designed for use in an office setting was

released with the Xerox Star 8010 in 1981. Although it was innovative, the Star was an

expensive ($17,000) system that was purchased by only a relatively small number of businesses

and institutions. After personal computers became more widespread, the first laser printer

intended for a mass market was theHPLaserJet 8ppm, released in 1984, using aCanon engine

controlled by HP software. The HP LaserJet printer was quickly followed by laser printers fromBrother Industries, IBM,Apple and others. First-generation machines had large photosensitive

drums, of circumference greater than the paper length. Once faster-recovery coatings were

developed, the drums could touch the paper multiple times in a pass, and could therefore be

smaller in diameter.

Laser printers brought fast, high quality text printing with multiple fonts on a page to the

business and consumer markets. No other commonly available printer could offer this

combination of features. As with most electronic devices, the cost of laser printers has fallen

markedly over the years. In 1984, the HP LaserJet sold for $3500, had trouble with even small,

low resolution graphics, and weighed 71 pounds (32 kg). Low end monochrome laser printers

often sell for less than $75 as of 2008. These printers tend to lack onboard processing and rely on

the host computer to generate a raster image (see Winprinter), but still will outperform the

LaserJet Classic in nearly all situations.
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4. WORKING

There are typically seven steps involved in the laser printing process:

Raster image processing

Each horizontal strip of dots across the page is known as a raster line orscan line.Creating the

image to be printed is done by a Raster Image Processor (RIP), typically built into the laser

printer. The source material may be encoded in any number of special page description

languages such as Adobe PostScript (PS,BR-Script), HPPrinter Command Language (PCL), or

MicrosoftXML Page Specification (XPS), as well as unformatted text-only data. The RIP uses

the page description language to generate a bitmap of the final page in the raster memory.

For fully graphical output using a page description language, a minimum of 1 megabyte of

memory is needed to store an entire monochrome letter/A4 sized page of dots at 300 dpi. At 300

dpi, there are 90,000 dots per square inch (300 dots per linear inch). A typical 8.5 11 sheet of

paper has 0.25-inch (6.4 mm) margins, reducing the printable area to 8.0 10.5 inches

(270 mm), or 84 square inches. 84 sq/in 90,000 dots per sq/in = 7,560,000 dots. Meanwhile 1

megabyte = 1,048,576 bytes, or 8,388,608 bits, which is just large enough to hold the entire page

at 300 dpi, leaving about 100 kilobytes to spare for use by the raster image processor.

In a color printer, each of the fourCYMK toner layers is stored as a separate bitmap, and all four

layers are typically preprocessed before printing begins, so a minimum of 4 megabytes is needed

for a full-color letter-size page at 300 dpi.

Memory requirements increase with the square of the dpi, so 600 dpi requires a minimum of 4

megabytes for monochrome, and 16 megabytes for color at 600 dpi. Printers capable of tabloid

and larger size may include memory expansion slots.
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Charging

Applying a negative charge to the photosensitive drum

In older printers, a corona wire positioned parallel to the drum, or in more recent printers, a

primary charge roller, projects an electrostatic charge onto the photoreceptor (otherwise named

the photo conductor unit), a revolving photosensitive drum or belt, which is capable of holding

an electrostatic charge on its surface while it is in the dark. AnACbias is applied to the primary

charge roller to remove any residual charges left by previous images. The roller will also apply a

DCbias on the drum surface to ensure a uniform negative potential. Numerouspatents describe

the photosensitive drum coating as a silicon sandwich with a photocharging layer, a charge

leakage barrier layer, as well as a surface layer. One version uses amorphous silicon containing

hydrogen as the light receiving layer,Boron nitride as a charge leakage barrier layer, as well as a

surface layer of doped silicon, notably silicon with oxygen or nitrogen which at sufficient

concentration resembles machiningsilicon nitride

Exposing

Laser neutralizing the negative charge on the photoreceptive drum to form an electrostatic image.
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The laser is aimed at a rotating polygonal mirror, which directs the laser beam through a system

of lenses and mirrors onto the photoreceptor. The cylinder continues to rotate during the sweep

and the angle of sweep compensates for this motion. The stream of rasterized data held in

memory turns the laser on and off to form the dots on the cylinder. Lasers are used because they

generate a narrow beam over great distances. The laser beam neutralizes (or reverses) the charge

on the black parts of the image, leaving a static electric negative image on the photoreceptor

surface to lift thetonerparticles.

Some non-laser printers expose by an array of light emitting diodes spanning the width of the

page, rather than by a laser ("exposing" is also known as "writing" in some documentation).

Developing

The surface with the latent image is exposed totoner,fine particles of dry plastic powder mixed

with carbon black or coloring agents. The charged toner particles are given a negative charge,

and are electrostatically attracted to the photoreceptor's latent image, the areas touched by the

laser. Because like charges repel, the negatively charged toner will not touch the drum where the

negative charge remains.

Transferring

The photoreceptor is pressed or rolled over paper, transferring the image. Higher-end machines

use a positively charged transfer roller on the back side of the paper to pull the toner from the

photoreceptor to the paper.

Fusing

Melting toner onto paper using heat and pressure.
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The paper passes through rollers in the fuser assembly where heat (up to 200 Celsius) and

pressure bond the plastic powder to the paper.

One roller is usually a hollow tube (heat roller) and the other is a rubber backing roller (pressure

roller). A radiant heat lamp is suspended in the center of the hollow tube, and its infrared energy

uniformly heats the roller from the inside. For proper bonding of the toner, the fuser roller must

be uniformly hot.

Some printers use a very thin flexible metal fuser roller, so there is less mass to be heated and the

fuser can more quickly reach operating temperature. If paper moves through the fuser more

slowly, there is more roller contact time for the toner to melt, and the fuser can operate at a lower

temperature. Smaller, inexpensive laser printers typically print slowly, due to this energy-saving

design, compared to large high speed printers where paper moves more rapidly through a high-

temperature fuser with a very short contact time

Cleaning

Magnification of color laser printer output, showing individual toner particles comprising 4 dots

of an image with a bluish background

When the print is complete, an electrically neutral soft plastic blade cleans any excess toner from

the photoreceptor and deposits it into a waste reservoir, and a discharge lamp removes the

remaining charge from the photoreceptor.

Toner may occasionally be left on the photoreceptor when unexpected events such as a paper

jam occur. The toner is on the photoconductor ready to apply, but the operation failed before it

could be applied. The toner must be wiped off and the process restarted.
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Multiple steps occurring at once

Once the raster image generation is complete all steps of the printing process can occur one after

the other in rapid succession. This permits the use of a very small and compact unit, where the

photoreceptor is charged, rotates a few degrees and is scanned, rotates a few more degrees and isdeveloped, and so forth. The entire process can be completed before the drum completes one

revolution.

Different printers implement these steps in distinct ways. Some "laser"printers actually use a

linear array oflight-emitting diodes to "write" the light on the drum (seeLED printer). The toner

is based on eitherwax orplastic,so that when the paper passes through the fuser assembly, the

particles of toner melt. The paper may or may not be oppositely charged. The fuser can be an

infrared oven, a heated pressure roller, or (on some very fast, expensive printers) a xenon flash

lamp.The Warm Upprocess that a laser printer goes through when power is initially applied to

the printer consists mainly of heating the fuser element.

5. MECHANISM

Non-impact printing is making a big impact in the electronic printing and computing industries.

In the North American market, the ratio of non-impact to impact printers shipped is now about

1:1. World-wide the trend is the same as rapid advances are made in thermal, electrophotographic (laser), ink-jet, and ionographic printing.Electro photographic, or more popularly,

laser printing technology will be dealt with in this section.

Laser printers currently represent the main bulk of non-impact printers in use today. Laser

printers have excellent print quality, low noise levels, high speed and the ability to print both

graphics and text. With the continued reduction in prices, laser printers have become a rapidly

growing market and consequently an area of intense technological focus. Laser printers range

from large machines used in a centralised data processing facility capable of printing 100

pages/minute and to unit with 4-6 pages/minute intended for the small single-user PC.

Electro photography was invented by Chester Carlson in 1938 and developed by Xerox Corp.

Initially the technology was used for plain-paper photocopiers. About 1976, Laser printer

development begun, and electrophotography was initially used in high performance machines.

Intense development efforts and hence market growth because of excellent print quality has
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brought about the gaining popularity for this printer. Its popularity and market volume has thus

brought about declining in prices

Laser printers have become commonplace in recent office automation. Laser printers, given its

wide range of product, support printing speeds up to tens of thousands of lines per minute.

Figure 1: Laser printer printing mechanism shows an internal construction of a typical laser

printer. The semiconductor laser directs a beam of infrared light onto the hexagonal scanner.

This mirror reflects the beam onto a light sensitive drum, forming a raster scan as the drum

rotates. The charging corona produces a positively charged dot on the drum, which is neutralised

wherever the laser beam strikes the drum surface. The pattern of dots produced by the laser beam

forms the complete image on the page. Toner adheres to the charged portions of the page as it

passes by the toner cartridge, and is fused onto the paper under heat.

Laser printer printing mechanism

Traditionally, High initial cost and reliability problem shunt low end user away from EP

technology. Canon got around the problems associated with multi-step printing process by


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packaging all of the troublesome parts into a cartridge which the customer could discard after

3,000 copies. This concept is know as the virtual reliability (if it breaks down, throw it away).

A typical laser printer is the Apple Laserwriter, which uses a Canon laser engine, and is

controlled by a MC68000-based microcomputer with 1.5MBytes of RAM and 500kBytes of

ROM. It is shown in diagrammatic form in Figure 2: Schematic diagram of Apple laserwriter.

Interfacing to the Laserwriter is via either 25-pin RS232c or 9pin RS422 D-type connectors, at

baud rates of either 1200 or 9600.

Schematic diagram of Apple laserwriter


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6. COLOR LASER PRINTERS

Fuji Xerox color laser printer C1110B

Color laser printers use colored toner (dry ink), typically cyan, magenta, yellow, and black

(CMYK).

While monochrome printers only use one laser scanner assembly, color printers often have two

or more scanner assemblies.

Color printing adds complexity to the printing process because very slight misalignments known

as registration errors can occur between printing each color, causing unintended color fringing,

blurring, or light/dark streaking along the edges of colored regions. To permit a high registration

accuracy, some color laser printers use a large rotating belt called a "transfer belt". The transfer

belt passes in front of all the toner cartridges and each of the toner layers are precisely applied to

the belt. The combined layers are then applied to the paper in a uniform single step.

Color printers usually have a higher cost per page production cost than monochrome printers.

DPI RESOLUTION

1200DPIprinters were commonly available during 2008. 2400 DPI electrophotographic printing plate makers, essentially laser printers that print

on plastic sheets, are also available.

7. ELECTROPHOTOGRAPHIC PROCESS

7.1 SUMMARY OF EP PROCESS

The general process of making a print utilising EP involves six steps:
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1. Charge- a photoconductive (PC) surface is exposed to a corona discharge to impart a uniform

electrostatic charge on its surface.

2. Expose- the charged photoconductor (PC) is exposed to a light pattern of the appropriate

wavelength to discharge it selectively. If discharge occurs in those areas that will eventually be

white in the final print, the process is called charged area (CAD) or direct development. If the

discharge occurs in areas to be printed black, it is called discharge area (DAD) or reversal

development.

3. Develop- black toner particles are transported by electrostatic or magnetic forces into the

vicinity of the PC. The toner particles are electro statically attracted to the appropriate areas on

the PC and the latent image is developed.

4. Transfer-the developed image is transferred from the PC to a sheet of paper by contacting the

PC with the paper.

5. Fuse- the transferred image is permanently fixed to the paper by pressure, heat or solvent

vapours.

6. Clean- the PC drum is cleaned of all excess toner by a scraper blade, brush or other means and

the EP system is ready to begin another cycle.

7.2 CHARGE

CORONASThe initiation of the EP process requires the deposition of a uniform charge layer onto the PC.

Corona charging is the only method used in modern electro photography.

The simplest corona device that could be used to charge a PC is a thin (~0.1 mm) wire charged to

5-7 kV. Because of the extremely high electric field in the vicinity of the thin corona wire,

electrons present naturally in the surrounding gas are accelerated to energies high enough to

ionise molecules and atoms in the gas. Depending on the direction of the field, either positive or

negative ions are swept out of the ionising region onto the insulating surface of the PC. One

important factor that determines the charge on the PC is the sign of the mobile charge in the PC.

Many inorganic PC's, Se for example, can most effectively transport negative charges when

illuminated, requiring the use of a positive surface charge. Most organic PC's, however, are

positive charge conductors and thus require a negative surface charge.

The requirement of coronas is in the charging step is very demanding. In this step, the corona

must lay down a uniform, well-controlled layer of charge on the PC. Nonuniformities in charge


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may result in nonuniformities in the printed copy. A simple way of controlling the uniformity of

both positive and negative coronas (and also preventing arcing from wire to PC) is to place a

grounded metal plate in the vicinity of the wire. This corona configuration is called a corotron,

which is shown in Figure 3 Corona configuration-Corotron.

Corona configuration-Corotron

The problems associated with the coronas are: Coronas are easily contaminated with toner or

paper dust, and is difficult to clean. Thus it represents a major reliability problem; They are

sources of corrosive ions, and reactive neutral species that can damage the PC as well as the

corona itself; They create ozone ( negative coronas produce an order of magnitude more ozone

than positive coronas).

7.3 PHOTOCONDUCTOR

PC is the heart of the EP process. This is the photoconductive element that bears the latent image

produced by light. The latent image is then developed by toner.The PC is expected to satisfy a variety of concurrent requirements: The PC must be capable of

charging to a uniform, high voltage level; On exposure to light, it must discharge to a voltage

level low enough to provide the necessary contrast in the developed image. The light induced

discharge must be rapid in relation to the process time of a print but there must be no significant

discharge in the dark; Residual potential should not build up even after repeated cycling; The PC


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7.5 MATERIALS

The earlier type of PC's involves the use of amorphous chalcogenide (S, Se, Te) alloys. Most

commonly used are a-Se, a-As2Se3 and Te doped Se. These materials have low dark decay and

high charge acceptance and can be manufactured inexpensively. The spectral sensitivity of these

materials is high in the visible range but low in the IR region.

Organic materials are relatively inexpensive to make and because of the wide variety of organic

molecules available, the spectral response can be tuned almost at will. Despite their softness and

consequent shorter lifetime they are widely used. The first organic was a mixture of

trinitrofluorenone (TNF) in polyvinylcarbazole (PVK).

To improve the efficiency of the PC and permit tailoring of wavelength response, layered

organic photoconductors are used. In these layered systems, the steps of charge generation and

charge transport are separated and optimised. The charge generation layer is a thin (~ 0.5 m)layer chosen to have high charge generation efficiency and to have a spectral response matched

to the wavelength of the light source. The charge transport layer is a thicker (20-30 m) layer.

Since most charge transport layers can only transport holes, a negative surface charge is

commonly produced by the corona.

7.6 PRINTHEADS

Figure 1: Laser printer printing mechanism shows the internal construction of a typical low costprinter using a semiconductor laser. First, the drum passes under the charging corona where a

uniform electrostatic charge is placed on the surface of the photoconductor drum.

The PC must be discharged by light in a pattern of dots of 240, 300 or 600 dots per inch (dpi).

Light from gas lasers, diode lasers, lamps, light emitting diodes (LED) and cathode ray tubes

(CRT) can be used to discharge the PC. All of these exposure methods require that the

wavelength of the light source overlap with the wavelength sensitivity of the PC and that the

light source itself can be switched on and off rapidly to scanned across a page and has sufficient

power to write at the desired speed.

Most of the EP printers available today utilise a laser printhead. The laser is either a gas

laser or a diode laser.


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Laser print head

In a laser system is the rotating polygon mirror. In such a system, a laser beam strikes a facet of a

multifaceted polygon mirror (8-36 facets) rotating at a speed of 2000-50,000 rpm. The beam is

reflected off a facet and swept across the PC surface. As the drum rotates, a raster-scan pattern is

produced on the surface of the drum in which at every point where the laser beam strikes the

drum, the electrostatic charge is neutralised. The pattern of neutralised dots forms the complete

image on the page. The charged image is later developed by passing the drum near the toner

cartridge. Another scanning technology is the holographic scanner. The hologram can be

designed to focus the beam onto the PC so that an additional lens would not be necessary.

Since gas lasers cannot be turned off and on quickly, an acoustic-optic modulator is used. Thismodulator consists of a piezoelectric transducer and modulation of the laser beam is

accomplished by turning the acoustic wave off and on. In diode laser, which can be directly

modulated by controlling the input current and therefore no separate modulation is necessary. In

LED's, CRT's, or fluorescent lamps with a multi-element shutter, each addressable line across the

PC surface corresponded to a light source array. Hence no scanner is required. These methods

require a printhead with many elements (> 2000 for a 300 dpi resolution), that could be rapidly

modulated and focused on the PC.

LED technology offers potential advantages over laser printheads. However, several problems

are related to this technology: A major set of packaging and electronic problems arise related to

integrating the over 2000 diodes into a single printhead (staggered or single row); The

availability of inexpensive gradient index lens arrays for focusing the LED emission onto the PC.


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An LED printhead assembly

Another type of light source used in EP printers is the cathode ray tube which has full electronic

control of scanning and modulation and maturity and consequently the reliability of CRT

technology.

A final type of printhead utilizes a light shutter array. The most promising of the light shutter

array technologies is the liquid crystal shutter.

8. DEVELOPMENT SYSTEMS

The development system provides a reproducible method for charging the toner particles,

transporting them into the development region where they are transferred to the latent image on

the PC. The most widely used development system today is the dual component magnetic brush

system.


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A dual component magnetic brush developer

In this system small (~ 10 m) toner particles are charged by contacts with the surface of much

larger (> 100 m) carrier particles. The toner is a polymer binder with a carbon blackpigment

and other additives to influence the sign and magnitude of the charging. The carrier can be either

a spherical or irregular shaped metallic core and may be bare or polymer coated. A rotating

aluminium sleeve with internal stationary permanent magnets carries chains of carrier beads

loaded with charged toner into the development region. The toner deposits onto oppositely

charged regions on the PC, and the larger carrier beads and unused toner are recycled and used

again. Sensors continuously monitor the toner concentration in the mix and replenish toner as it

is used.

8.1 FUSING

Toner particles, which are only weakly attached to the paper surface must become permanently

fixed. Fusing involves three physical processes: coalescence or sintering together of toner

particles into a single mass; spreading of the coalesced melt across the paper surface and

penetration of the melt into the paper fibres interstices by capillary action. These steps are


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accomplished by elevating the temperature and/or pressure applied to the toner. Most EP printers

today use hot roll contact fusing.

8.2 CLEANING

To prepare the EP system for another cycle, all residual toner must be removed from the PC

before the charging process takes place again. This can be accomplished by three methods: a

blade, a soft fibre brush, or a magnetic brush. The most straightforward method is to scrape the

residual toner off the photoreceptor. A simple metal or polymeric blade will do an effective job

for low end electrophotographic applications. Brushes made of fur and fibre have been used in

high end products.

9. LASER PRINTER MAINTENANCE

Most consumer and small business laser printers use a toner cartridge that combines the

photoreceptor (sometimes called "photo conductor unit" or "imaging drum") with the toner

supply bin, the waste toner hopper, and various wiper blades. When the toner supply is

consumed, replacing the toner cartridge automatically replaces the imaging drum, waste toner

hopper, and wiper blades.

Some laser printers maintain a page count of the number of pages printed since last maintenance.

On these models, a reminder message will appear informing the user it is nearing time to replace

standard maintenance parts. On other models, no page count is kept or no reminder is displayed,

so the user must keep track of pages printed manually or watch for warning signs like paper feed

problems and print defects.

Some color laser printers, notably some Lexmark models run "calibration" cycles even when no

printing has occurred for weeks. These are widely reported to waste a significant amount of toner

from each reservoir, in addition to consuming electricity. This has a significant impact on

printing economy, especially in low-volume applications. On some models these calibration

cycles can be disabled via a menu choice, for others the printer must be unplugged to avoid this

waste. Printers that have this issue have a replaceable "waste toner bin", which is another

periodic operating expense.


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Manufacturers usually provide life expectancy charts for common printer parts and consumables.

Manufacturers rate life expectancy for their printer parts in terms of "expected page-production

life" rather than in units of time.

Consumables and maintenance parts for business-class printers will generally be rated for a

higher page-production expectancy than parts for personal printers. In particular, toner cartridges

and fusers usually have a higher page production expectancy in business-class printers than

personal-class printers. Color laser printers can require more maintenance and parts replacement

than monochrome laser printers since they contain more imaging components.

For rollers and assemblies involved in the paper pickup path and paper feed path, typical

maintenance is to vacuum toner and dust from the mechanisms, and replace, clean, or restore the

rubber paper-handling rollers. Most pickup, feed, and separation rollers have a rubber coating

which eventually suffers wear and becomes covered with slippery paper dust. In cases where

replacement rollers are discontinued or unavailable, rubber rollers can be cleaned safely with a

damp lint-free rag. Commercial chemical solutions are also available which may help

temporarily restore the traction of the rubber.

The fusing assembly (also called a "fuser") is generally considered a replaceable consumable part

on laser printers. The fusing assembly is responsible for melting and bonding the toner to the

paper. There are many possible defects for fusing assemblies: defects include worn plastic drive

gears, electronic failure of heating components, torn fixing film sleeves, worn pressure rollers,

toner buildup on heating rollers and pressure rollers, worn or scratched pressure rollers, and

damaged paper sensors.

Some manufacturers offer preventative maintenance kits specific to each printer model; such kits

generally include a fuser and may also include pickup rollers, feed rollers, transfer rollers, charge

rollers, and separation pads.


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BIBLIOGRAPHY

http://en.wikipedia.org/wiki/Laser_printer http://www.webopedia.com/TERM/L/laser_printer.html http://tomax7.com/aplus/APlusCD/Lazer%20Printer%20Notes.doc http://www.lintech.org/comp-per/14LASER.pdf http://www.dpc.com/downloads/Troubleshooting-Generic.pdf
http://www.webopedia.com/TERM/L/laser_printer.htmlhttp://www.lintech.org/comp-per/14LASER.pdfhttp://www.lintech.org/comp-per/14LASER.pdfhttp://www.webopedia.com/TERM/L/laser_printer.html

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