Xerox ColorQube 9303 Series Service Manual page 1768

The IOD module enables a variety of system functions on the ColorQube. Its primary function
is to align the four printheads to create a seamless image. This is called head-to-head align-
ment, or H2H alignment. A second function is to adjust the jetting intensity of the heads, again
to maintain consistent intensity across the entire image. This is called head-to-head intensity,
or H2H intensity. Intensity for the whole printhead is set at once, jets cannot be individually
adjusted for intensity. A third function is to detect and correct weak and missing jets by substi-
tution, a process known as jet masking.
IOD Operational Sequence
The IOD sequence is only performed from standby state. The IOD sequence typically occurs
every 500 pages. The printer stops and performs an IOD rear scan then waits another 500
pages and performs IOD front scan. Scans continue to alternate between rear and front every
500 pages. Manually activated scans are executed from diagnostics. The technician selects
either a front or rear IOD scan.
When an IOD sequence is executed, the following steps are performed:
1. A drum maintenance cycle is performed to prepare the drum for imaging.
2. The scan bar is moved to the rear (or front) position. The unmarked drum surface is read
with and without illumination to establish black and white calibration levels. This is done
while the drum is rotating, so that an average is achieved. After calibration, the scan bar
moves to the park position, which is the approximate center of travel of the IOD assembly.
3. The target image is jetted onto the drum.
4. The scan bar is moved to the rear (or front) position. A snapshot of the image is acquired
by the IOD by rotating the drum with the target image across the scan bar. After the IOD
has acquired the image, the scan bar is protected and then moved to the park position.
5. The acquired target is analyzed to calculate head position.
6. Appropriate head position corrections are calculated and applied. There are four types of
corrections:
• Each printhead has a small motor to adjust printhead rotation in the radial axis. The
IOD correction step immediately moves these motors.
• Each printhead has a Y-axis offset value from the drum home position that controls
jet timing for all jets on that head during imaging. The IOD correction step updates
these Y-offset values.
• Each SFWA has an X-Axis offset value from the SFWA home position that controls
the starting position of the SFWAs during imaging. The IOD correction step updates
these X-offset values.
• Each SFWA has a head that is fixed, and a second head with a small motor to adjust
X-position relative to the fixed head. The IOD correction step immediately moves
these motors.
7. A cleaning unit cycle is performed to scrape the target image from the drum.
IOD Sequence Types
Since the IOD cannot see one of the printheads during a scan, it is unable to correct head
alignment for all four heads in one scan sequence. In its present form, the IOD system is only
able to correct printhead alignment based on what it sees during that sequence. Also, it does
not retain scan data to be interpreted by a subsequent scan sequence to provide a single
adjustment covering all printheads.
The IOD has no home sensor. It drives fully in one direction until it stalls and assumes it is fully
forward or rearward. Then it counts clock pulses to the central park position.
Principles of Operation
Table 1 Measurement and corrective Actions for Front and Rear IOD Scans
Table 1 Measurement and Correction Actions for Front and Rear IOD Scans
Head Positions Front Scan
Head 1 Roll Measure and adjust.
Head 2 Roll Measure. Do not adjust.
Head 3 Roll Measure. Do not adjust.
Head 4 Roll Cannot be measured during a
front scan. Adjustment cannot
be performed.
Head 1 Y-offset Measure and adjust.
Head 2 Y-offset Measure. Do not adjust.
Head 3 Y-offset Anchor.
Head 4 Y-offset Cannot be measured during a
front scan. Adjustment cannot
be performed.
Head 1 X-stitch Measure and adjust.
Head 2 X-stitch Measure. Do not adjust.
Head 3 X-stitch Anchor.
Head 4 X-stitch Cannot be measured during a
front scan, Adjustment cannot
be performed.
IOD reads drum run out at home (from the drum encoder) and at 6 degree intervals. These val-
ues are stored and used to set Y axis run out variance of timing of the jets on the printheads.
This calibration should be performed whenever the drum encoder is serviced (which may
change the home position) or whenever the drum is changed (which will change the run out).
IOD Printhead efficiency maintenance
The efficiency of the printheads is measured by Closed Loop Dropmass (CLD) calibration.
There are two CLD measurement processes, cldBaseline and cldAdjust. The cldBaseline pro-
cess measures the efficiency of each printhead when it is first installed onto a printer (time
zero). The value of the cldBaseline measurement is stored in the machines NVRAM. The cld-
Adjust process measures the efficiency of each printhead periodically over it's life time, and
applies incremental head-drive voltage adjustments to maintain the original printhead effi-
ciency captured by the cldBaseline process at time zero.
The cldAdjust and cldBaseline process are similar and include the following steps;
• Calibration of the IOD scanbar sensor.
• Render and print measurement target into the drum surface.
• Scan an image of the drum surface using the IOD scan bar.
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Rear Scan
Cannot be measured during a rear
scan. Adjustment cannot be performed.
Measure and adjust.
Measure and adjust.
Measure and adjust.
Cannot be measured during a rear
scan. Adjust as if stitched to printhead
2.
Measure and adjust.
Anchor.
Measure and adjust.
Cannot be measured during a rear
scan. Adjust as if stitched to printhead
2.
Measure and adjust.
Anchor.
Measure and adjust.
ColorQube® 9303 Family