Xerox DocuColor 12/DCCS50, Service Manual

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Overview
Principles of Operation
Reissue
Overview
This module describes the electrical and mechanical components of the Xerographics process.
Xerographics includes these primary functions:
• Providing a charge to the Photoreceptor Drum which can then be exposed with a laser for
the image data. This creates a latent image on the Photoreceptor Drum.
• Develop the latent electrostatic image on the Photoreceptor Drum by depositing toner
onto the image areas.
• Transfer the developed image from the Photoreceptor Drum to the Intermediate Transfer
Belt (IBT). The IBT receives all required toner colors before the image is transferred to the
paper.
• Transfer the complete toner image from the IBT to the paper.
• Clean both the IBT and the Photoreceptor Drum of developer residue.
• Suppling developer to the Developer Rotary Assembly
The major sections in this module are:
• Photoreceptor Drum
• Charging
• Development
• Toner Supply
• Intermediate Belt Transfer (IBT)
• Motors
• Cleaning Systems
• Air Flow
• Process Controls
The Xerographics processes in this machine use a number of design improvements which
helps it achieve the full color copy rate of 12.5 copies per minute. Unlike other color copier
technology that has the developed image on the Photoreceptor Drum layering one color at a
time directly onto the paper, this machine makes use of a subassembly called the “Intermedi-
ate Belt Transfer” (IBT). The IBT receives and accumulates all four color toner layers from the
Photoreceptor Drum, and then passes this completed image onto the paper in one pass. Using
this process there are actually two steps for image transfer. These are:
1. The charged and developed image on the Photoreceptor Drum is transferred to the Inter-
mediate Belt Transfer (IBT). The IBT accepts the image from the Photoreceptor Drum,
one color at a time, until all four colors are layered on top of each other on the IBT.
Layering sequence: YMCK, where Y is the first color put onto the Photoreceptor Drum
and transferred onto the IBT.
2. The complete colored image on the IBT is transferred to the final copy material in one
pass.
Layered sequence: KCMY, where K is the bottom color layer that is on the copy material
and Y is the top color layer.
Figure 1 Two Step Image Transfer Process
The advantage of the IBT is that it provides a more stable and consistent base than paper for
receiving the toner from the Photoreceptor Drum. When transferring four different toner layers
onto a substrate, factors such as: registration, surface charge, consistent transport speed,
moisture content, and surface texture all are critical variables that impact quality of that toner
transfer process. The wide variety of copy materials (different paper/plastic surfaces and
weights) make it difficult to control these variables, which impacts the color toner layering pro-
cess.
By using the IBT, the variables of surface charge, speed, registration, moisture content and sur-
face texture are either eliminated or reduced. This allows for more consistency in building the
toner layers. Once all the required image layers have been accumulated onto the IBT, this final
image is then passed onto the paper at the 2nd Bias Transfer Roll (BTR) through a controlled,
electrically charged, roller nip. By using one pass to transfer the complete image onto the
paper, an increase in image quality, image consistency and color copy rate is achieved.
Because of this two step transfer process, the image on the IBT is an upside-down, mirror
imaged and reversed colored layered of the image that ends up on the copy material. Refer to
Figure 1 for more information on this two step image transfer process.
IBT Belt
Photoreceptor Drum