Xerox Phaser 8860, Service Manual

Page: 306 / 316

09/2007
8-14 Phaser 8860/8860MFP Service Manual
Image Output Terminal
Initial Issue Theory of Operation
Figure 9 Drum Oiling
Printing
To print, the Drum starts rotating at a speed dependent upon print resolution. As the Drum
reaches the correct speed, the jets begin to fire to deposit the image on the oiled portion of the
Drum. As the jets fire, the Printhead moves from right to left to complete the image on the
Drum.
When printing, the system performs a “six-jet interlace,” in which each jet lays down a particular
number of pixel columns, depending on the print resolution. Each jet lays down one pixel col-
umn for each Drum rotation, which varies from eight to 16 rotations, depending on the print res-
olution. Interlacing “averages out” the variability between jets by interlacing each jet with other
jets. In some test prints, the Printhead moves to the right and lays down 309 parallel bands of
ink. Each band is composed of 15 pixel columns of dots from an individual jet.
Jet substitution allows a better performing jet to be used in place of a missing or poorly per-
forming neighboring jet. When jet substitution is used, the Printhead makes a second right-to-
left movement to deposit the pixel columns of the substituted jets. See
Jet Substitution Mode .
Ink Loader
The Ink Loader consists of four parallel channels with an ink melting element at the end of each
channel. Ink sticks, one color loaded in each channel, are pressed by coil spring pressure into
the melting elements. As ink is required by the Printhead, the appropriate color’s melting ele-
ment is activated and the end of the ink stick is melted. The melted ink drips into the ink reser-
voirs of the Printhead underneath. Sensors in the Ink Loader alert the customer to install more
ink sticks before the current sticks are completely consumed.
If the ink level sensors inside the Printhead detect that the Printhead has run out of ink, but the
ink low/out sensors are not activated, the Control Panel reports an “Ink Jam” error.
Figure 10 Ink Loading
Printhead
The Printhead is the heart of the system, spanning nearly the length of the drum. Using its
1236 jet nozzles (309 jets for each primary color), with a horizontal motion of slightly less than
5 mm (0.2 inches), the Printhead can print the entire image on the rotating drum. The Print-
head provides one size ink drop that it uses for all print-quality modes.