User manual

Rockwell Automation Publication MOTION-UM003F-EN-P - March 2015 175
Chapter 8
Home an Axis
Homing puts your equipment at a specific starting point for operation. This
starting point is called the home position. Typically, you home your equipment
when you reset it for operation.
When using Integrated Motion on the EtherNet/IP network, all active and
passive homes are setting absolute positions as long as an absolute device is being
used.
See the Integrated Motion on the EtherNet/IP Network Reference Manual,
publication MOTION-RM003
, for more details about the Homing attributes.
Guidelines for Homing
This table describes guidelines for homing procedures.
Topic Page
Guidelines for Homing 175
Active Homing 176
Passive Homing 176
Examples 177
Absolute Position Recovery (APR) 182
Table 21 - Guidelines for the Homing Procedures
Guideline Description
To move an axis to the home position, use Active
homing.
Active homing turns on the servo loop and moves the axis to the home position. Active homing also does the following:
• Stops any other motion.
• Uses a trapezoidal profile.
For a Feedback-only device, use Passive homing. Passive homing doesn’t move the axis:
• Use passive homing to calibrate a Feedback-only axis to its marker.
• If you use passive homing on a servo axis, turn on the servo loop and use a move instruction to move the axis.
For single-turn equipment, consider homing to a
marker.
The marker homing sequence is useful for single-turn rotary and linear encoder applications because these applications
have only one encoder marker for full axis travel.
For multi-turn equipment, home to a switch or switch
and marker.
These homing sequences use a home limit switch to define the home position:
• You need a home limit switch if the axis moves more than one revolution when it runs. Otherwise, the controller can’t
tell which marker pulse to use.
• For the most precise homing, use both the switch and marker.