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Thermal Jet
Appendix B: Theory of Operation
Thermal Jet Operations Manual Rev M
Page 33
Appendix B: Theory of Operation
Thermal Jet Print Heads
TIJ Technology
The print head uses Thermal Ink Jet (TIJ) technology as implemented on the hp
®
45A car-
tridge. TIJ technology works by rapidly heating the ink. As the ink heats it expands and is
ejected from the print cartridge orifices. Because the individual orifices are very small,
many more can be compacted in the same amount of space as conventional print technol-
ogies. With more orifices per vertical inch / millimeter, a much higher resolution image can
be produced.
Similarities and Differences
A print head can operate stand-alone or in concert with other print heads connected one to
another in a daisy chain configuration. Up to eight 1/2" Print Heads or four 1" print heads
can be daisy chained. Print heads can be controlled by the Handheld controller, from a PC
or laptop using the included GUI software interface program, or by a user developed appli-
cation.
Print heads can print up to five lines of print, using any combination of the various print field
types supported, including fixed text, date/time codes, product counts, variable fields,
logos, and a variety of bar codes, including Data Matrix 2-D codes.
Unlike other inkjet technologies, these print heads store and process the currently printing
message internally. This allows the print heads to be disconnected from the controlling
device and operate "stand alone" once the print information has been uploaded to the
heads. However, print head and print message status is unavailable to the the controlling
device once the print heads are disconnected.
Ink Cartridge Ink Status
Each ink cartridge contains approximately 42 mL of ink and has been programmed to make
full use of the
Smart Level Ink Detection System
. When a new cartridge is snapped into
a print head it is given an identity code so that its ink level may be monitored. As the ink
depletes to 10% ink remaining, an "Ink Low" condition occurs and the red LED on the rear
of the print head turns on steady. The red LED changes to slow flashing, indicating "Ink
Out", when there is minimal ink remaining, and significant print degradation is imminent.
Ink status is reported back to the Handheld controller or GUI software as long as they are
connected to the print head daisy chain.