Process Control - Xerox Phaser 6500 Service Manual

Theory of Operation

Process Control

Potential Control
Toner Density Control
2-44
For stable printing, the parameters related to the image development must be
corrected as necessary. The process control is performed in two methods after
every 25 cumulative prints, upon termination of a print run, or during a continuous
run.
• Potential Control
• Toner Density Control
The following controls supplement the above controls:
• High Area Coverage Mode
• Admix Mode
To attain stable image density, the drum charging voltage, the developing DC
voltage, and the Laser Unit beam intensity are adjusted according to the
developing capability of each color carrier. The adjusted drum charging voltage,
the developing DC voltage, and the Laser Unit beam intensity are fed back to keep
the printing image density constant.
The outline of controls is as follows:
1. The Humidity Sensor detects humidity and temperature.
2. The patches of respective colors (Yellow, Magenta, Cyan, and Black) for the
potential control are generated and transferred on the transfer belt.
3. The ADC Sensor (Density Sensor) detects the density of the patch on the Belt.
4. The drum charging voltage, developing DC voltage, and the Laser Unit beam
intensity are adjusted for each color according to the detected patch density.
Toner density must be kept constant to attain stable printing. The control system
for this purpose is called toner density control.
1. PCDC (Pixel Count Dispense Control)
The amount of toner to be consumed in the developing process is calculated
by counting the pixels sent to the Laser Unit. The amount of toner to be
consumed is calculated by the toner dispensing time. The toner motor is
driven for the calculated toner dispensing time when supplying the toner to
the Developer.
2. ADC (Auto Density Control)
The patches of respective colors (Yellow, Magenta, Cyan, and Black) for the
toner density control are generated under a specified potential condition, and
transferred on the Belt. The ADC Sensor measures this density, and the
measured value is compared with reference value. If the toner density is low,
the toner dispense quantity is increased at the next printing, or if the toner
density is higher, the toner dispense quantity is reduced at the next printing.
The toner dispense quantity is calculated by the toner dispense time. This
calculation is made for each color.
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Phaser 6500/WorkCentre 6505 Service Manual