Readhead Mounting And Alignment; Reference Mark Set-Up - Renishaw RGH40 RESR40 Installation Manual

Readhead mounting and alignment

Mounting brackets
The bracket must have a flat mounting surface, and should provide adjustment to enable conformance to
the installation tolerances, allow adjustment to the rideheight of the readhead, and be sufficiently stiff to
prevent deflection or vibration of the readhead during operation.
Readhead set-up
Ensure that the scale, readhead optical window and mounting face are clean and free from obstructions.
To set nominal rideheight place the Blue readhead spacer with the 'L' shaped aperture under the optical
centre of the readhead to allow normal LED function during set-up procedure.
Adjust the readhead to maximise the signal strength and achieve a Green set-up LED over the full rotation.
NOTE: Ensure readhead fixing screws are tightened to 0.5 Nm to 0.7 Nm.
An external set-up signal, X, is also available on RGH40 readheads for use where the LED is not visible.
See 'Output specifications' for further details.
Pitch
0° ±1°
Readhead set-up LED status except
at reference mark position
Green Orange Red
RGH40 RESR installation guide
Yaw
0° ±1°
Roll
0° ±1°
Blue spacer
Rideheight
0.8 ±0.15 mm

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.
Ensure the readhead is set up correctly ensuring a Green LED indication over the full rotation.
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 'Output specifications'.
Phasing procedure
The readhead must be moved 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
1
by turn and the procedure repeated
8
until a Red flash is obtained.
1
turn
8
Readhead set-up LED flash during reference mark traverse only
Red Orange Blank
9