Carriage Drive Mechanism - Brother MFC620CN Service Manual

3.2.2.4

Carriage drive mechanism

The head/carriage unit, which integrates the print head unit and carriage, is supported and guided
by the CR guide rail and CR support chassis. The CR timing belt (1/25.4 inch pitch) transmits the
carriage motor rotation to the carriage. Clockwise motor rotations move the carriage to the right;
counterclockwise ones to the left.
The CR encoder sensor on the back of the head/carriage unit scans the CR encoder strip under the
engine chassis to monitor the current head position relative to the home position. The controller
uses this signal for proportional, integration, differential (PID) control ensuring uniform speed. The
strip's 1/150 dpi markings offer a choice of four speeds to match the print resolution: 40.0, 33.3,
32.0, and 20.0 ips.
CR encoder strip
Idle pulley
Aging
Maintenance mode function code 69 is for adjusting the initial PWM value. The firmware
automatically adjusts this CR drive parameter as the head/carriage unit works to minimize speed
deviations and to match the current mechanism. This aging sometimes resolves problems with ink
clogging uneven operation.
For further details on maintenance function code 69, see
CR timing belt
CR support chassis
CR guide rail
Head/carriage unit
Chapter 8, Section
3-37
(Paper feed roller)
Carriage
motor pulley
Carriage motor
8.5.17.
Confidential