Dot matrix printing
Dot matrix printing or impact matrix printing is a
type of computer
printing which uses a print head that runs back and forth, or in an
up and down motion, on the page and prints by impact, striking an ink-soaked
cloth ribbon against the paper, much like the print mechanism on a typewriter. However, unlike
a typewriter or daisy
wheel printer, letters are drawn out of a dot matrix, and thus,
varied fonts and arbitrary graphics can be produced.
Design
Each dot is produced by a
tiny metal rod, also called a "wire" or "pin", which is
driven forward by the power of a tiny electromagnet or solenoid, either directly
or through small levers (pawls). Facing the ribbon and the paper is a small
guide plate pierced with holes to serve as guides for the pins. This plate may
be made of hard plastic or an artificial jewel such as sapphire or ruby.[1] The moving
portion of the printer is called the print head, and when running the printer
generally prints one line of text at a time. Most dot matrix printers have a
single vertical line of dot-making equipment on their print heads; others have
a few interleaved rows in order to improve dot density.
Because
the printing involves mechanical pressure, these printers can create carbon copies and carbonless
copies. Its speed of printing varies from 50 to 500 cps.
These
machines can be highly durable. When they do wear out, it is generally due to
ink invading the guide plate of the print head, causing grit to adhere to it;
this grit slowly causes the channels in the guide plate to wear from circles
into ovals or slots, providing less and less accurate guidance to the printing
wires. Eventually, even with tungsten
blocks and titanium pawls, the
printing becomes too unclear to read.
Although
nearly all inkjet,
thermal, and laser printers also print
closely spaced dots rather than continuous lines or characters, it is not
customary to call them dot matrix printers.
The
LA30 was a 30 character/second dot matrix printer introduced in 1970 by Digital Equipment Corporation of Maynard,
Massachusetts. It printed 80 columns of uppercase-only 5x7 dot matrix characters
across a unique-sized paper. The printhead was driven by a stepper motor and the paper
was advanced by a somewhat-unreliable and definitely noisy solenoid ratchet drive. The
LA30 was available with both a parallel interface and a serial interface;
however, the serial LA30 required the use of fill characters during the
carriage-return operation.
The
LA30 was followed in 1974 by the LA36, which achieved far greater
commercial success, becoming for a time the standard dot matrix computer
terminal. The LA36 used the same print head as the LA30 but could print on
forms of any width up to 132 columns of mixed-case output on standard green bar
fanfold paper. The carriage wa
s moved by a much-more-capable servo drive using a DC electric motor and an optical encoder / tachometer. The paper was
moved by a stepper motor. The LA36 was only available with a serial interface
but unlike the earlier LA30, no fill characters were required. This was
possible because, while the printer never communicated at faster than 30
characters per second, the mechanism was actually capable of printing at 60
characters per second. During the carriage return period, characters were buffered
for subsequent printing at full speed during a catch-up period. The
two-tone buzz produced by 60 character-per-second catch-up printing followed by
30 character-per-second ordinary printing was a distinctive feature of the
LA36.
Digital
then broadened the basic LA36 line onto a wide variety of dot matrix printers
including:
- LA180: 180 c/s line printer
- LS120: 120 c/s terminal
- LA120: 180 c/s advanced terminal
- LA34: Cost-reduced terminal
- LA38: An LA34 with more features
- LA12: A portable terminal
In
1970, Centronics (then of Hudson,
New Hampshire) introduced a
dot matrix printer, the Centronics 101. The search for a reliable printer
mechanism led it to develop a relationship with Brother Industries, Ltd of Japan, and the sale of Centronics-badged
Brother printer mechanisms equipped with a Centronics print head and Centronics
electronics. Unlike Digital, Centronics concentrated on the low-end line printer marketplace
with their distinctive units. In the process, they designed the parallel electrical interface
that was to become standard on most printers until it began to be replaced by
the Universal
Serial Bus (USB)
in the late 1990s.
Sumber:http://en.wikipedia.org/wiki/Dot_matrix_printing
Nama:Rifky Darmawan
No. Absen:21
Kelas:9C
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