Aligning The Disc - Renishaw ATOM Installation Manual

Aligning the disc

There are two possible ways to accurately align the disc to minimise eccentricity:
Optical alignment using a microscope
u
Electrical alignment using two readheads
u
The method chosen to align the disc on the system depends upon the application and available
space, etc. It should be noted that the graduations and alignment band are accurately concentric
with each other but not with the glass disc. The following sections outline how to align the disc
using these methods.
NOTE: The disc should not be mounted on the black mask on the reverse of the disc
(apart from 17 mm disc).
Optical alignment
This method uses a microscope, which could be connected to a camera,
to monitor the movement of the alignment band as the disc is rotated.
1
Position the microscope/camera over the alignment band on the disc so that any
displacement of the alignment band due to rotation of the disc/hub assembly
can be observed.
Alignment
band
ATOM
rotary installation guide
Microscope
and camera
RCDM disc/hub
assembly
Contact your local Renishaw representative for more information on aligning the disc.
2
Rotate the disc/hub assembly and observe the maximum and minimum limits of movement
of the alignment band as shown below.
Minimum movement
0° Rotation 90° Rotation
3 Note the axis position at the limits of movement.
4
Rotate the disc so either of these limits of movement is located under the microscope.
5
Gently move the disc relative to the hub in a radial direction so the alignment band
moves half way between the limits of movement.
NOTE: The alignment band is 30 µm wide.
Position of disc at limit of movement of alignment band.
Direction of
movement
6
Rotate the assembly and repeat steps 3-5 until the total alignment band
movement is within the design specifications.
7
Cure the adhesive.
8
Recheck the run-out.
Maximum movement
180° Rotation 270° Rotation
Alignment band
Microscope
Position of maximum or
minimum limit of movement
of the alignment band
6