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Laser Printers
Although Inkjet printers are fast, the less
expensive Inkjet models on the market today are not speedy enough
to keep up with the demands of a busy office, where performance
and reliable paper handling are a must- you'll need a more
expensive, high-end Inkjet printer for office use. Inkjet ink
tends to smear when wet. Finally, Inkjet printers tend to suffer
from banding on large areas of black or a single color. If you've
ever tried to print a large illustration using solid black on an
Inkjet or dot matrix printer, you've seen this effect: visible
bands running horizontally across the image. Because the print
head can apply only a small rectangle of ink, any misalignment of
the paper or minute difference in the ink mixture results in a
band. These disadvantages may not be tremendously important to
the owner of a home PC, but office workers need the best possible
print quality, and they need those pages yesterday. For this
reason, either a high-end inkjet printer or laser printers are
better suited for a networked office environment. Laser printers
have been around for years now, but most of us remember why they
weren't popular for home or small office use. As little as five
years ago, the least expensive laser printer available would
still set you back at least $1,000. Prices have dropped to the
point where that same $1,000 will buy you an office- quality
laser printer that delivers pages at 16 pages per minute at 1,200
dpi- And, in fact, prices for many "personal" laser printers have
dropped to less than $400, making them affordable for the home
user who wants best monochrome and grayscale documents.
In this section let's discuss the inner workings of
both monochrome and color laser printers, as well as other
features you'll find on most lasers that make them the right
choice for an office setting.
How Do Laser Printers Work?
Is a laser printer the same as a laser copier? Not
really instead of scanning input from a hard copy document, a
laser printer accepts its input of the original image as a series
of codes from your computer. Your laser printer's microprocessor
uses these codes to build an image of the page in the printer's
internal memory, which it then transfers to the printed page.
(This is why you often see the RAM or buffer memory listed in
advertisements for laser printers.)
Your laser printer also uses toner instead of ink.
Toner is a very fine black powder that is very sensitive to
electric charges. Luckily, you usually don't have to pour toner
into your printer; as with an inkjet, you simply replace a
cartridge to add more toner to virtually all laser printers.
Laser toner cartridges use a roller to spread a wide, continuous
layer of toner over the length of the cartridge.
But how does that toner stay on the paper, and what
arranges it to form text and graphics? Let's follow the laser
printing process step by step:
- A roller moves across the face of a turning cylinder inside
your laser printer; the charging roller transfers an electrical
charge to the cylinder, which is called photoconductor. As
mentioned earlier, toner powder is very sensitive to electrical
charges, and this charge repels the toner powder away from the
photoconductor.
- The photoconductor cylinder keeps turning, which next brings
it into contact with a laser beam. (It had to be called a "laser
printer" for some reason.) The laser beam is controlled by the
printer's microprocessor brain, which turns the beam on and off
as it sweeps back and forth across the surface of the
phtoconductor. Areas struck by the laser beam reverse the
electrical charge, so the toner sticks to just the imaged areas
of the photoconductor cylinder.
- The next stop for the photoconductor cylinder is another
roller - this one is the tone roller, which dispenses an even
line of toner across the face of the photoconductor. Those areas
of the cylinder that have been hit by the laser beam attract
toner, while the rest of the toner still repels it. In effect,
the cylinder now carries an image of the page, but it hasn't yet
been transferred to the paper.
- As the photoconductor continues to turn, it comes in contact
with the transfer roller - paper from the paper tray is
simultaneously fed between the two surfaces. The transfer roller
applies a slight electrical charge to the paper, so the toner
that remains on the photoconductor cylinder now sticks to the
paper. (At this point, however, the toner is not actually affixed
to the page; it would fall off if you shook the page.)
- Now our attention turns to the paper - it passes trough
another two rollers. The top roller, which is on the same side of
the paper as the toner, is called the fuser roller; it's heated
by the printer, so the toner partially melts and sticks to the
page for a permanent bond. To provide pressure, another roller
simultaneously presses the paper against the fuser roller.
- As the two rollers turn, the paper is drawn through them and
moves outside the machine to the paper collection tray.
- Now that the photoconductor cylinder has transferred the
image to the page, it must be cleaned before the process can
repeat. As the cylinder continues to turn, it passes under a
cleaning brush or a scraper blade that removes any stray
particles of toner.
- Finally the photoconductor cylinder completes the cycle by
returning to the charging roller; if another page has to be
printed, the entire process is repeated.
Color laser printers follow this same general
process, but they use four color toners instead of one.(Sometimes
these colors are added as individual cartridges or poured
individually into the unit, while other printers combine all of
the separate color toner cartridge.) The photoconductor cylinder
in a color printer makes four complete passes to transfer each of
the four base colors to the page before it passes to the fuser
roller. As you can imagine, these printers are far more complex
and require more internal memory to hold four separate images of
the same page, so even with the drop in monochrome laser prices,
a color laser printer can still set you back several thousand
dollars.
The office choice
Traditionally, laser printers have been the top
sellers for office environments (although inkjet printers are
rapidly growing in popularity as technology improves). Besides
the advantages listed earlier in this section, laser printers
also have a number of other features that make them especially
attractive for heavy printing traffic:
High printing speed. Although inkjet
technology is improving in speed, high-performance laser printers
can still double the output speed of even the best inkjet printer
in monochrome printing, making laser printers the favorite in nay
office that requires a high volume of printing.
Network capable. Most laser printers have an
option for a network connection, which simplifies their use as a
network printer. (Some high-end inkjet printers also offer
built-in network support.)
Improved paper handling. Laser printers can
usually hold more paper than an average inkjet printer, meaning
the paper supply lasts longer and requires less intervention.
Many models (as do most inkjets) also come with accessory trays
that enable you to use legal and European paper sizes.
Resident fonts and font cartridges. Many
older models of laser printers can be upgraded with additional
on-board fonts through font cartridges, while today's models are
upgraded with internal font memory cards; because windows doesn't
have to download these fonts to your printer each time you print
a document. On-board fonts can save you anywhere from 15 to 30
seconds of printing time. The more you use a specific font in
your documents, the more you'll benefit if you add that font
cartridge to your laser printer.
Warning
The fuser roller is exposed on many laser printers
when you open the cover, and if the printer has been running,
this roller is often hot. It's important not to touch the fuser
roller, and pay close attention to any warning labels or stickers
inside your laser printer when your replacing toner cartridges or
cleaning the interior mechanism.
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