Inkjet printers are one of the most common type of printers in
use these days. Their advantages include a very low
inital cost, as little as $50 for a low-end model such as
the EPSON Stylus C40UX, significantly less then the cost
of a laser printer, and good color output. Disadvantages
include a relatively high cost per page, usually around
10 times the cost of laser printers, and relatively slow
pages per minute speeds of around 4 to 8ppm for black and white
and 2 to 4ppm for color.
Most inkjets work using thermal technology where tiny
dots of ink are fired at the paper through heat. A small
resistor heats the ink in a chamber untill a bubble is
formed. This bubble forces the ink out of the chamber onto
the paper. Multiple chambers are arranged on the print head
and fire as the print head is moved back and forth across
the paper. In most color inkjet printers their are chambers for
cyan, magenta, yellow and black inks, the CYMK colors.
Some printers leave out the
black and instead form it by mixing cyan, magenta and yellow.
However doing this can't give a true black as the colors
never really mix properly; it's also wastefull of expensive
color ink.
A slightly different method used by Epson used a piezo
crystal instead of a heating resistor. The peizo crystal
changes shape in response to electric current, this forces ink out
of the nozzle just like the heater-based printers. However
the peizo crystal provides better control then a heating
resistor allowing for smaller dot sizes and higher
resolution.
The two main factors affecting printer quality is
the resolution, measured in dpi, (dots per inch) and the
number of levels, or graduations, that can be printed per
dot. Most printers opt for a trade-off, some opting for
higher resolution and others opting for more levels per
dot. Business users usually need high resolution for crisp
letters, graphics designers need more graduations to give
more realistic color. Most printers can print up to
1440x720dpi (1440 dots horizontally, 720 vertically) with
around 4 to 16 levels of color per dot. Some printers
can print multiple drops of ink on one dot. For instance
printers with Hewlett-Packard's PhotoREt colour
layering technology can print over 30 individual drops of
ink per dot, allowing for thousands of possible colors
per dot.
Two types of ink are commonly used in inkjet printers,
slow drying and deep penetrating and fast drying ink. The
former takes up to 10 seconds to dry, this makes
it rather prone to smudging and more sutable for monochrome
printing. The latter drys around 100 times faster and is
better suted for color printing as when different inks are
mixed they need to dry quickly to avoid blurring. Nearly
all inks used today are water based. This unfortunately
poses problems with smudging and running. It also means
that like most printed materials the ink is not very water
resistant. Laser printers, with their "baked-on" toner,
are better in this respect.
Most good printers will have two cartridges, one for
black ink and one for color. This saves on costs by
allowing you to just replace the black, or color, ink if
that's all you've run out of. Some printers even go and
seperate the color cartidge into seperate cartridges for
the cyan, magenta and yellow. Another factor is the actual
print head. Some printers, usually heat based printers,
have integrated ink cartidges and print heads. Others, such
as many of Epson's peizo crystal based printers, have a
permanent print head. Some even have both a replacable
print head and ink cartidge! Print heads can tend to clog
up, especially if the printer isn't used regularly, so a
replacable print head can be an advantage. However the
print heads usually will last for a lot longer then the
ink and a integrated ink/print head will cost more.
-- generic-man notes that most cheap printers are sold at below cost, so that the manufacturers recoup the costs when you buy ink cartridges. Ever wonder why those third-party cartridges are never sanctioned by the manufacturers?
For photo-quality output most inkjet printers require
special high-quality coated or glossy paper which can be
very expensive. For most monochrome uses however plain
copier paper is sufficient. Most manufactures sell special
papers that are optimized for the specific technologies used
in their printers, though this paper tends to be
significantly more expensive then generic papers. For
instance paper can be pre-conditioned with a agent that
helps bind the pigment to the paper. However these agents
are specific to whatever type of ink is used by that
manufacture.
Other alternatives to inkjet printers
include laser printers,
dot matrix printers and
dye sublimination printers.
- "The PC Technology Guide - Inkjet Printers" - http://www.pctechguide.com/13inkjets.htm
- "How Inkjet Printers Work" - http://www.howstuffworks.com/inkjet-printer.htm