Have you ever wondered how your inkjet printer works?
How does the ink get from the inkjet cartridge to the paper? Why is
the print quality is so clear? Why the printing is so quiet?
Generally, all that most people know is that there's some movement
and a faint high pitched sound when it's printing something -- and
then the finished document comes out.
Unlike dot matrix and character printers that strike ribbons to
create an image, inkjet printers do not physically touch the paper.
All inkjet printers function using the same basic principles. Tiny
ink droplets are "jetted" (or pushed) out multiple holes onto paper
in a controlled and systematic fashion. This is where the term
"inkjet" comes from.
The size of ink droplets, speed and reliability of this type of
printer has been continuously improving since its inception in 1976.
In 1993, Epson was the first manufacturer to produce an inkjet
printer using micro-piezo technology. The Epson Stylus 800 was the
first printer to use the multi-layer actuator printhead (the
printhead is the part of the printer that holds numerous tiny
nozzles that actually squirts the ink onto paper).
This specific printhead utilized an electro-mechanical element that
acted like a tiny control room. When pulses of electricity passed
through, it that gave specific signals to fire individual or
multiple nozzles loaded with ink.
Micro-piezo technology utilized a tiny crystal in each individual
nozzle that when electrically energized, would vibrate or bend
causing a controlled amount of ink to be forced out onto paper. When
the electrical current is off, the crystal bends back to its
original shape, creating a vacuum, thus pulling ink into the nozzle
from the reservoir for the next commanded fire.
The Epson printhead was fixed to the carriage so it never needed
replacing (the printer carriage is what moves laterally across the
paper). This also kept the cost of ink cartridges low since they
were little more than reservoirs of ink.
This breakthrough printer produced a whopping 360 dpi (dots per
inch) that was deemed, almost "letter quality" at the time. With a
printing speed of 150 - 180 characters per second, the new Epson
became the user favorite printer for home and office.
At the same time, HP was using a similar technology. A thermal
jetting system was utilized in their printhead. The printhead still
acted like the control room but each individual nozzle was instead
independently super heated by electricity, which caused the ink to
explode onto the paper. HP claims the temperature of a fired inkjet
nozzle approaches that of the surface of the sun.
HP elected to put the printhead on the inkjet cartridge itself
instead of mounting it permanently to the carriage. Since each
inkjet cartridge would have its own printhead, replacement
cartridges would be more expensive for these printers.
HP inkjet cartridges also could not print as fast as Epson because
each nozzle needed to cool after firing. This heating technology
also limited the types of inks that could be used.
In the 1990's, Canon, Epson and HP engineered printheads that
applied even smaller droplets of ink, drastically improving dpi and
While Canon and HP could produce a 6 - 10 picoliter droplet size
from one nozzle, Epson was about half the size (between 3 - 6
picoliters). Currently, there are printers available which will
produce an amazing 1 picoliter droplet! To get an idea of how small
this is; a human hair is about 12 picoliters in diameter. Most human
eyes can't see one jetted droplet of ink on paper.
Inkjet printers have come a long way since their first inception.
Printers today are twice as fast as their predecessors were, and are
cheaper than ever. Many printers can easily produce color photo
quality images in at an incredible 6000 dpi.
As time goes on and as demand for printing remains high, the
quality, speed and features of inkjet printers will only continue to
Bob Stephens is director of operations for ASAP
Inkjets, and an authority on inkjet technology & mechanics