User manual

Rockwell Automation Publication MOTION-UM003F-EN-P - March 2015 179
Home an Axis Chapter 8
Active home to switch and marker in forward
bidirectional
This is the most precise active homing sequence available.
These steps occur during the sequence.
1. The axis moves in the Home Direction at the Home Speed to the home limit switch and stops.
2. The axis reverses direction and moves at the Home Return Speed until it clears the home limit switch.
3. The axis keeps moving at the Home Return Speed until it gets to the marker.
4. The axis moves back to the marker or it moves to the Offset position. The axis moves at the Home Return Speed. If the
axis is a Rotary Axis, the move back to the Home Position takes the shortest path (that is, no more than ½ revolution).
If the axis is past the home limit switch at the start of the homing sequence, the axis reverses direction and starts the return
leg of the homing sequence.
Active home to switch in forward unidirectional This active homing sequence is useful for when an encoder marker is not available and either unidirectional motion is
required or proximity switch is being used.
These steps occur during the sequence.
1. The axis moves in the Home Direction at the Home Speed to the home limit switch.
2. The axis moves to the Home Offset position if it’s in the same direction as the Home Direction.
Active home to marker in forward unidirectional This active homing sequence is useful for single-turn rotary and linear encoder applications when unidirectional motion is
required.
These steps occur during the sequence.
1. The axis moves in the Home Direction at the Home Speed to the marker.
2. The axis moves to the Home Offset position if it’s in the same direction as the Home Direction.
Active home to switch and marker in forward
unidirectional
This active homing sequence is useful for multi-turn rotary applications when unidirectional motion is required.
These steps occur during the sequence.
1. The axis moves in the Home Direction at the Home Speed to the home limit switch.
2. The axis keeps moving at the Home Speed until it gets to the marker.
3. The axis moves to the Home Offset position if it’s in the same direction as the Home Direction.
Table 22 - Active Homing Examples (Continued)
Sequence Description
Homing Vel
Return Vel
Axis Position
Axis Velocity
1
2
4
3
1: Home Limit Switch Detected
2: Home Limit Switch Cleared
3: Encoder Marker Detected
4: Home Position
Active Bidirectional Home with Switch then Marker