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82 • Chapter 6 Programming Motion DMC-3425
Electronic Gearing (Local Mode)
This mode allows one axis to be electronically geared to the other axis. The master may rotate in both
directions and the geared axes will follow at the specified gear ratio. The gear ratio may be different
for each axis and changed during motion.
The command GA specifies the master axis. GR n,n specifies the gear ratios for the slaves where the
ratio may be a number between +/-127.9999 with a fractional resolution of .0001. There are two
modes: standard gearing and gantry mode. The gantry mode is enabled with the command GM. GR
0,0 turns off gearing in both modes. A limit switch or ST command disables gearing in the standard
mode but not in the gantry mode.
The command GM n,n selects the axes to be controlled under the gantry mode. The parameter 1
enables gantry mode, and 0 disables it.
GR causes the specified axes to be geared to the actual position of the master. The master axis is
commanded with motion commands such as PR, PA, or JG.
When the master axis is driven by the controller in the jog mode or an independent motion mode, it is
possible to define the master as the command position of that axis, rather than the actual position. The
designation of the commanded position master is by the letter C. For example, GACD indicates that
the gearing is the commanded position of D.
Electronic gearing allows the geared motor to perform a second independent or coordinated move in
addition to the gearing. For example, when a geared motor follows a master at a ratio of 1:1, it may be
advanced an additional distance with PR, JG, VP, or LI commands.
Command Summary - Electronic Gearing
COMMAND DESCRIPTION
GA n Specifies master axes for gearing where:
n = A,B for main encoder as master
n = CA, CB for commanded position.
GR n,n Sets gear ratio for slave axes. 0 disables electronic gearing for specified axis.
GM n,n 1 sets gantry mode, 0 disables gantry mode
MF n,n Trippoint for forward motion past specified value. Only one field may be used.
MR n,n Trippoint for reverse motion past specified value. Only one field may be used.
GA? Retuns the GA command setting
Example – Electronic Gearing
Objective: Gear an A-axis slave motor at a speed of 2.5 times the speed of the B-axis master.
GAB Specify B-axis as the master for A
GR2.5 Specify gear ratio for A to be 2.5 times the B axis master.
Example - Gantry Mode
In applications where both the master and the follower are controlled by the DMC-3425 controller, it
may be desired to synchronize the follower with the commanded position of the master, rather than the
actual position. This eliminates the possibility of an oscillation on the master passing the oscillation on
to the slave.