Rockwell Automation 8520 9/Series CNC Integration Maintenance Manual Documentation Set - Manual (Page 702)

Integrating a Split Axis with Deskew
Section 14B
14B-8
Figure 14B.4
Encoder Marker Positioning Relative to the Home Limit Switch
Off On
CORRECT
Off On
INCORRECT
Home
limit switch
Home
limit switch
SLAVE
MASTER
Master and slave
encoder markers are
aligned and positioned
slightly away from where
the home limit switch
transitions from on to off.
This insures that both
servos will rotate a short
distance in the same
direction to find the
nearest marker.
Master and slave
encoder markers are
aligned but are positioned
nearly 180 ° from the home
limit switch transition. This
results in a lot of servo
motion to find the nearest
marker and makes it
unpredictable which way
each servo will rotate.
Optimal
marker
zone
Optimal
marker
zone
Optimal
marker
zone
Optimal
marker
zone
SLAVE
MASTER
Optimal
marker
zone
Optimal
marker
zone
Optimal
marker
zone
Optimal
marker
zone
Important: The following step is crucial to attain a repeatable home
position and to assure both servos home to the same relative location. If
the home switch cannot be moved, you should attempt to re-align the
encoder markers (repeat steps 4. through 10.) to a location close to the
home limit switch.
15. Position the home limit switch. Loosen the home limit switch and
slide it against the axis or switch dog until it switches on. Then move
it away from the axis until it just switches off. Move it a slight
distance further and tighten it securely. (You may have to alter this
step to accommodate the “direction to home” and “direction to move
off limit switch” parameter settings for your machine.)
When the control homes an axis, it homes to the closest marker at the
instant the home limit switch transitions from on to off. You should
position the encoder markers close to but not directly at the trip point for
the home limit switch as shown in Figure 14B.4.