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Inkjet Printers
By Stephen Bucaro
Because Laser printers use a process similar to photography, they will always
produce higher resolution results than inkjets printers. Laser printers are
also faster than inkjet printers. Laser printers cost less to operate because
inkjet cartridges are expensive and need to be changed more frequently than
toner cartridges, and because special coated paper is required to produce
high-quality output on an inkjet printer.
HP Color Inkjet Printer
But the initial cost of an inkjet printer is much less than a laser printer,
and inkjet printers are required for certain projects, for example they can
handle heavy cardstock better for producing greeting cards. An inkjet printer
is also required to print on iron-on transfer paper. Laser printers can't be
used to print on iron-on transfer paper because they use heat.
In operation, a print head moves horizontally across the page and colored
ink droplets are squirted at the paper. Inkjet print heads contain between 300
and 600 nozzles, each about the diameter of a human hair. Typically between
four and eight cyan, magenta, yellow, and black colored ink droplets are
combined to create halftone colors.
The print head doesn’t print just a single row of pixels, but a vertical row
of pixels in each pass. The paper is then advanced to print the next vertical
strip. Since paper is 8.5 inches wide, at a minimum 300 dpi, there are about
2,475 dots across the page.
There are two main inkjet technologies, thermal and piezo-electric. Thermal
technology (referred to as Bubblejet by Canon), uses silicon wafer heating
elements to rapidly super heat and vaporise a small volume of ink. The
vaporised ink expands, forcing tiny droplets through a nozzle.
Epson Color Inkjet Printer
Epson uses a proprietary piezo electric technology. Piezo technology applies
an electric charge to a piezo electric crystal. The electric charge causes the
piezo electric crystal to flex, forcing an ink droplet out the nozzle.
The piezo electric process allows more control over the shape and size of ink
droplets. Also, the ink doesn't have to be heated, which allows greater freedom
in the formulation of the ink.
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