Datasheet

Installation and Configuration of Printers 77
FIGURE 1.32 The writing step of the EP process
EP drum
Rotating mirror
Direction of
rotation
Laser scanning
assembly
Laser
beam
Fixed
mirror
Step 4: Developing Now that the surface of the drum holds an electrical representation of
the image being printed, its discrete electrical charges need to be converted into something
that can be transferred to a piece of paper. The EP process’s developing step accomplishes
this (Figure 1.33). In this step, toner is transferred to the areas that were exposed in the
writing step.
FIGURE 1.33 The developing step of the EP process
Toner
Blade
Reservoir
EP drum
Developing
cylinder
EP drum
Toner fog
Nonexposed areas
Nonexposed areas
Exposed areas
A metallic developing roller or cylinder inside an EP cartridge acquires a –600VDC charge
(called a bias voltage) from the HVPS. The toner sticks to this roller because there is a mag-
net located inside the roller and because of the electrostatic charges between the toner and
the developing roller. While the developing roller rotates toward the photosensitive drum, the
toner acquires the charge of the roller (–600VDC). When the toner comes between the devel-
oping roller and the photosensitive drum, the toner is attracted to the areas that have been
exposed by the laser (because these areas have a lesser charge, of –100VDC). The toner also
is repelled from the unexposed areas (because they’re at the same –600VDC charge, and like
charges repel). This toner transfer creates a fog of toner between the EP drum and the devel-
oping roller.
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