2-16 Phaser 8400/8500/8550 Color Printer
Drum Assembly And Transfix System
The drum assembly and transfix system form the key portion of the printer where
imaging takes place. The drum assembly and transfix system are separate, yet
interrelated. This section discusses the drum assembly. The next section provides
more detail on the transfix system.
In operation, the image to be printed on paper is first “printed” on the rapidly rotating
drum. The paper preheater heats a sheet of paper or transparency film to prepare it for
the image transfer process. The heated paper is then passed between the drum (now
rotating much more slowly) and the transfix roller. The pressure between the drum
and the transfix roller transfers the image to the sheet of paper. An encoder disk and
sensor on the left end of the drum monitors the drum’s speed and position.
The drum heater heats the surface of the drum to about 60
o
C (140
o
F) for imaging.
The drum heater does not rotate. The heater is inside the drum, and is controlled by
the drum heater relay board. The drum heater consists of two resistive heater coils that
operate in series for 220 V and in parallel for 110 V operation. The drum heater relay
board controls the series/parallel operation. A temperature sensor in contact with the
drum surface monitors the drum temperature. The main board interprets the sensor’s
signal and turns on the drum heater and drum fan to heat the drum, or turns on the
drum fan alone to cool the drum.
Paper Preheater
Transfix Roller
Paper Path
Drum
Drum Heater
s8500-019
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