Rockwell Automation Publication 2080-UM002L-EN-E - November 2021 113
Chapter 7 Motion Control
MC_HOME_ABS_SWITCH
MC_HOME_ABS_SWITCH (0) homing procedure performs a homing
operation against the home switch. The actual motion sequence is dependent
on the home switch, limit switch configuration, and the actual status for the
switches before homing starts—that is, when the MC_Home function block is
issued.
Scenario 1: Moving part at right (positive) side of home switch before homing starts
The homing motion sequence for this scenario is as follows:
1. Moving part moves to the left side (negative direction);
2. When home switch is detected, the moving part decelerates to stop;
3. Moving part moves back (positive direction) in creep velocity to detect
home switch On→Off edge;
4. Once home switch On→Off is detected, record the position as
mechanical home position, and decelerate to stop;
5.
Move to the configured home position. The mechanical home position
recorded during moving
back sequence, plus the
home offset configured
fo
r the axis in the Connected Components Workbench software.
Scenario 2: Moving part is in between Lower Limit and Home switch before homing starts
The homing motion sequence for this scenario is as follows:
1. Moving part moves to its left side (negative direction);
2. When lower limit switch is detected,
the moving part decelerates to stop,
or stop immedi
ately, according to limit switch hard stop configuration;
3. Moving part moves back (in positive direction) in creep velocity to detect
home switch On→Off edge;
4. Once home switch On→Off edge is detected, record the po
sition as
mechanica
l home position, and decelerate to stop;
5.
Move to the configured home position. The mechanical home position
recorded during moving
back sequence, plus the
home offset configured
fo
r the axis in the Connected Components Workbench software.
Scenario 3: Moving part on Lower Limit or Home switch before homing starts
The homing motion sequence for this scenario is as follows:
1. Moving part moves to its right side (in positive direction) in creep
velocity to detect home switch On→Off edge;
2. Once home switch On→Off edge is detected, record the po
sition as
mechanica
l home position, and decelerate to stop;
3. Move to the configured home position. The mechanical home positi
on
recorded dur
ing moving right sequence, plus the home offset configured
for the axis in the Connected Components Workbench software.
IMPORTANT
If home switch is not configured as enabled, MC_HOME_ABS_SWITCH (0)
homing fails with MC_FB_ERR_PARAM.
If Lower Limit switch is not configured, or not wired, the homing motion fails,
and moves continuously to the left until the drive or moving part fails to
move.
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