134 Rockwell Automation Publication MOTION-RM002H-EN-P-February 2018
Changing Master Axes
The master axis for electronic gearing can be changed at any time, even while
gearing is currently enabled. However, since it is possible to have electronic gearing
enabled on more than one axis at a time, if a Servo master axis and slave axis are
reversed, the axes become cross-coupled and unexpected motion may result.
For example, if you are gearing Axis 0 to Axis 1 (defined as a Servo axis) and then
want to change to gearing Axis 1 to Axis 0, you must first disable gearing on Axis 0
(see Disable Gearing later in this section). This is because specifying Axis 1 as the
slave axis with Axis 0 as the master axis does not automatically disable Axis 0 from
being a slave axis with Axis 1 as the master axis.
Move While Gearing
An incremental MAM instruction may be used for the slave axis (or master axis if
the Axis Type is configured as Servo) while the electronic gearing is enabled. This
is particularly useful to accomplish phase advance/retard control. The incremental
move distance can be used to eliminate any phase error between the master and the
slave, or to create an exact non-zero phase relationship. Incremental MAM
instruction may also be used in conjunction with electronic gearing to compensate
for material slip.
Normally a gear ratio of 1 is used with phase adjustment. A 1:1 ratio ensures that
the computed phase error does not change before performing the move to correct
it. Electronic gearing is not normally used with absolute moves, since the ultimate
endpoint is not predictable.
To successfully execute a MAG instruction, the targeted axis must be configured as
a Servo Axis Type and the axis must be in the Servo On state. If any of these
conditions are not met than the instruction errors.
Important:
The MAG instruction execution completes in a single scan, thus the Done (.DN) bit and the In Process (.IP) bit
are set immediately. The In Process (.IP) bit remains set until the initiated Gear process is superseded by
another MAG instruction, or terminated by a Motion Axis Stop command, Merge operation, or Servo Fault
Action.
In this transitional instruction, the relay ladder, toggle the Rung-condition-in
from cleared to set each time the instruction should execute.
Affects Math Status Flags
No
Major/Minor Faults
None specific to this instruction. See Common Attributes for operand-related
faults
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