Readhead mounting and alignment
Mounting brackets
The bracket must have a flat mounting surface, ensure conformance to the installation
tolerances, allow adjustment to the rideheight of the readhead, and be sufficiently stiff to
prevent deflection of the readhead during operation. For easier installation, the bracket
should be adjusted for roll and yaw with respect to the axis of readhead travel before the
scale is applied using the appropriate applicator. This can be done with a clock gauge
and precision square.
Readhead set-up
Ensure that the scale, readhead optical window and mounting face are clean and free
from obstructions. To set nominal rideheight place either the Blue or Orange readhead
spacer should be positioned with the aperture under the optical centre of the readhead
to allow normal LED function during set-up procedure. The Orange spacer also helps to
position readhead with respect to offset and yaw relative to the scale. Adjust the readhead
to maximise the signal strength along the full axis travel to achieve a Green set-up LED.
An external set-up signal (X or V
X
) is also available on RGH41 readheads for use where
the LED is not visible. See ‘Output specifications’ for details.
NOTE:
Ensure readhead fixing screws are tightened to 0.5 Nm-0.7 Nm.
Reference mark set-up
To ensure uni-directional repeatability, the reference mark requires phasing with the scale
in the direction of normal datuming operation. A reference pulse is output in both directions,
but repeatability is guaranteed only in the phased direction.
The readhead should be set up correctly ensuring a Green LED indication over the full
length of travel. The reference mark actuator should be installed as shown on the
installation drawing.
NOTE:
It is recommended that a datum procedure is performed as part of any power-up
sequence to ensure the correct datum position is recorded.
NOTE:
Reference mark output is synchronised with the incremental channels, giving unit of
resolution pulse width. For further details see ‘General specifications’.
Phasing procedure
Move the readhead over the reference mark in the direction to be used for the datuming
operation. The reference mark is phased correctly when the set-up LED flashes Red for
0.25 seconds. If it flashes Orange or goes blank, the reference mark adjuster screw
should be turned anti-clockwise by
1
8
turn and
the procedure repeated until a Red flash
is obtained.
1
8
turn
RGH41 RGS40 installation guide
7
Rideheight
0.8 ± 0.15 mm
Pitch
0° ±1°
Roll
0° ±1°
Orange spacer
or
Blue spacer
Yaw
0° ±1°
Green Orange Red
Readhead set-up LED status
Red Orange Blank
Readhead set-up LED flash during
reference mark traverse only
Limit switch
Limit switch detection is entirely independent of other readhead functions - the signal is only output
when the readhead is positioned over the limit switch actuator.