To perform the paper feed, the printer catches the paper in between the Drive Roller and the Pinch
Rollers (Pinch Rollers are spring-loaded pushing the paper down on top of the Drive Roller), then the
paper is pushed forwards on top of the Print Platen in the print zone, which is where the printing
operation is performed. The paper advance is provided by a motor that moves the Drive Roller. The
exact position of the Drive Roller and hence the paper is controlled by an Encoder Disk located on the
roller axis.
The printed paper then passes between the Output Shaft and the Starwheels (which keep the paper
tension as flat as possible for printing) to exit on the Output Platen, where it is held in case of cut sheet
or is cut to fall on the output basket in the case of roll paper.
The Output Shaft is designed to over-advance the Drive Roller movement slightly, and hence create the
necessary paper tension to keep the paper as flat as possible. The Starwheels are spring-loaded and
are designed to create force on top of the paper, this is done so as to leave the paper unmarked and at
the same time allow the Output Shaft force to be appropriately transmitted.
In the Roll configuration, the rewinder module generates back force while printing to facilitate paper
control.
A key electrical element of the paper path is the Paper Sensor (also known as the Out-Of-Paper Sensor
or OOPS). This sensor is located at the beginning of the Print Platen; it detects paper insertion for roll
load and single-sheet load.
Electronics
In the paper-path driving system, the only electrically active element is the Drive Roller. The Drive Roller
is impelled by the drive roller motor and it contains an Encoder Disk on the axis to determine its
position. The Encoder Disk is read by two sensors. One, the encoder sensor, designed to read the
encoder, counts the Encoder Disk (the Encoder Disk outer marks) and another one, the encoder index
sensor, determines the start position (the 0 position) of the Drive Roller by reading the inner thicker
lines of the Encoder Disk.
NOTE: Every time the printer starts up, it searches for the 0 position of the Drive Roller. If this search
fails (which means that the index sensor is faulty), the printer will give a system error and will be unable
to initialize.
ENWW
Subsystems
11
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