Carriage Moving Unit; Platen Gap Adjustment Unit - Epson Stylus PRO 7500 Service Manual

EPSON Stylus Pro 7500

CARRIAGE MOVING UNIT

IIn place of the carriage holding system in which 2 CR guide shafts extending in the column
direction were used, as in the previous models, a structure with the carriage mounted via
multiple rollers (bearings) on a CR guide rail made from a square extruded aluminum pipe
is used. Steel rails are incorporated in the roller contact and running surface, and the result
is a reduction in friction in the direction of movement, reduced vibration and improved
durability.
NOTE: The screws used to fasten the CR guide rail should not be taken out and
the carriage should not be removed. These are adjusted and assembled to
the nearest 1/100 mm at the factory.
A DC motor is used for the CR motor and the slit in the timing fence affixed on the bottom
of and parallel with the CR guide rail is read by the encoder sensor mounted on the carriage
(linear encoder system), and this signal is compared to logical control values in the control
circuit on the C299 MAIN board , which carries out feedback speed control. Through this
control, high print precision is maintained.
Drive transmissions from the CR motor to the carriage use the easy-to-maintain, durable
timing belt.
The sensors used in the carriage moving unit are described below.
o
CR_HP Sensor
This is a transmissive photosensor which is mounted on the right end of the printer
mechanism and detects the entry position of the flag (projection) provided on the
carriage as the carriage moving home position. Outputs from this sensor are
"OFF" in the HP range and "ON" outside the HP range.
o
Linear Encoder
This encoder is mounted on the back of the carriage and outputs pulses (2
channels) corresponding to the position of the slit on the timing fence that is
incorporated into the CR guide rail which are used for CR motor servo control and
PTS (Print Timing Signal) generation. The resolution is 1/180 inch.
Operating Principles
CR_HP Sensor
(Mounted on the
mechanism's right
end.)
Encoder Sensor
(On Carriage)
CR Motor
Figure 2-2. Carriage Mechanism Unit, Carriage Moving Unit

PLATEN GAP ADJUSTMENT UNIT

In order to maintain the print precision, it is necessary to maintain the carriage (= head)
mounting position so that it is always a constant distance from the surface of the paper.
In this printer, the print head nozzle surfaces and platen surface are variable mechanisms so
that the gap between the paper printing surface and the head nozzle surface can be kept
constant.
The carriage has a 2-body construction with a sub-carriage on which the print heads are
mounted attached to the carriage which forms the base. The sub-carriage moves in the
vertical direction with respect to the paper surface. This movable system uses a cam. The
sub-carriage to paper surface distance changes linearly from the cam (= PG) home position.
Print Mechanism Components
Revision A
CR Guide Rail (projected
area)
Outside HP range Inside HP Range
Step Ruler
(Slitted Plate)
Encoder Sensor
Carriage
CR Timing Belt
HP Flag
CR_HP
Sensor
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