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2-14 Phaser 8400/8500/8550/8560 Color Printer Service Manual
Theory of Operation
Purge System
Proper Printhead operation is dependant on the correct operation of the purge
system. The purge system uses air pressure and a Wiper Blade to purge any
debris or air bubbles that may be obstructing the Printhead nozzles. The
waste ink that is expelled during the purge is funneled into the Waste Tray.
Following the purge, a wipe operation is performed on the faceplate using the
Wiper Blade. After the wipe, a Cleaning page is printed.
To perform a Printhead maintenance cycle, the Printhead is first tilted away
from the Drum, to allow the Wiper Blade to pass by. The Wiper Blade is then
raised in front of the Printhead. Wiper movement is driven by the Media Path
Drive, by engaging a clutch on the exit shaft of the printer. The Purge Pump
applies pressure to the ink reservoir for approximately 2.5 seconds. Valves in
the reservoir seal when pressure is applied. The pressurization ejects a small
amount of ink from the jets. Following the pressure purge, the Printhead is
tilted into the wiper assembly and the wipe cycle begins. The pump runs again
with the solenoid for approximately 30 seconds, creating a neutral balance
between pressure and ink. The Wiper Blade lowers and wipes excess ink
from the jets into the ink Waste Tray. A proper purge will layer the length of the
Waste Tray with a single layer of ink about 20 mm wide.
The level of the ink in the reservoir is kept at a constant level. If the purge
tubing is pinched, the Printhead may not purge properly. In addition, because
the purge tubing also acts as a vent to atmosphere when not purging, a more
serious failure may occur if the ink overfills. Overfilling may trap air in the
reservoir, which would prevent the melted ink from entering the reservoir.
s8500-017
Wiper Blade
Printhead
Purge Pump
Purge Tube
2.5 sec