Phaser 3600 Operational Overview; Summary Of The Printing Process - Xerox Phaser 3600 Service Manual

Theory of Operation

Phaser 3600 Operational Overview

Summary of the Printing Process

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The Phaser 3600 Laser Printer is a desktop monochrome laser printer,
applying the principals of an electrophotographic system to place a
monochrome image onto the print media. The system contains a drum and
developing unit which places the toner image onto print media producing
monochrome prints through the transfer unit.
The printing process is composed of the following:
Charging: The charge roller is negatively charged at approximately -1400
VDC by the high voltage power supply (HVPS). The charge roller is kept in
contact with the drum surface to provide a uniform negative charge of
approximately -800 VDC on the drum surface as it rotates at a constant
speed.
Exposure: The Laser Scan Unit (LSU) emits laser beams in response to
image data from the Main board. The laser beams are directed onto the drum
surface through a system of mirrors and lenses. A rotating polygonal mirror
causes the laser beams to scan the drum surface from end to end (axially) as
it rotates. The beams are turned on to print a pixel and off when no printing is
required. The negative charge on the drum surface is reduced to
approximately -250 VDC at each point where the energized laser beam
strikes, to form an invisible electrostatic latent image on the drum surface.
Development: Negatively charged toner particles from the toner hopper are
applied to the supply roller and are then applied to the developer roller in a
even layer controlled by the metering blade. The developer roller turns against
the drum and the toner particles are attracted to the relatively positive latent
image. The toner forms a visible image on the drum surface.
Pre-Clean: The pre-transfer Lamp exposes the developed surface of the
drum lowering the surface potential and thereby providing enhanced transfer
efficiency.
Transfer: The finished toner image on the drum is transferred onto the print
media using the voltage supplied by the Transfer Roller. The conductive
Transfer Roller receives a high positive voltage (approximately +1000 VDC)
from the HVPS that puts it at a higher potential than the drum. Since the
Transfer Roller is located behind the print media, the toner image is attracted
to the high potential and deposits on the surface of the print media.
Fixing: The finished toner image is impermanent and easily smeared. To fix
the image, the print media goes through the Fuser where it passes between a
pressure roller and the Heat Roller. The toner is fused onto the print media by
the combination of heat and pressure.
The Heat Roller is heated by a heat element. The roller surface temperature is
detected by a Thermistor. The information is fed back to the heater control to
maintain a surface temperature of 185º C during printing and 145º C during
standby. If the thermostats detect a Fuser overheat condition, it disconnects
AC power to the Fuser.
Cleaning: After the image is transferred to the print media, a cleaning blade
inside the cartridge removes any remaining toner particles from the drum.
Phaser 3600 Printer Service Manual