PRINTER DESCRIPTION
6--4 27080 Issue 1 September 98
The print head slides into a protective holster and is locked into place
by a screwinthe rear. The holster is mounted in the printing position
and contains precisionguiderails to ensure that theprint headalways
returns to exactly the same position if the print head is removed and
replaced.
Ink jet. The ink jet is created by the drop generator assembly, which
consists of the gunbody, fitted with a nozzle plate through which the
inkjetemerges. Thegunbodycontainsadriverodwhichgeneratesthe
ultrasonic pressure waves into the ink. The drop generator also has a
heater built into it with the temperature controlled by a sensor
embedded into the gunbody wall. Heating the ink reduces the effects
of variations in ambient temperature and improves drying times with
certain inks. A solenoid--operated plunger seals the nozzle when the
jet is switched off.
The control system includes a bleed function which increases the ink
flow through the drop generator and sweeps out any traces of air or
solid material.
Jet break--up. The ink jet breaks up into separate drops within the
chargeelectrode,bycarefulcontrolover theinkviscosityandthedrive
rod vibration.
The electronic system also maintains a close control over the timing of
the charge voltages on the charge electrode relative to the drop
formation.
The ink jet can be seen through a lens in the print head holster as it
passes through the charge electrode. It is made visible by the
stroboscopic effect of an LED pulsed in synchronism with the ink
drops.
Jetdeflection. Thedeflectorplatesaremountedoninsulatingbobbins
to isolate their high voltages. These voltages are not hazardous due to
protection circuits which make the voltages instantly collapse on
contact. The plates areangledto allow for greaterdeflectionhowever,
thisisnotthecasewithPinpointasitdoesnotrequireawiderdeflection
range.
Jet alignment. The ink jet is directed into the gutter by adjusting the
alignment of the drop generator (and therefore the nozzle) using a
special cam mechanism.
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