Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 409)

Axis Motion
Chapter 14
14-33
Figure 14.18
Automatic Return From Machine Home, Results of Example 14.13
Machine home
200
150
100
50
200 150 100 50
X
Y
N40
N30
N30
N20
N10
Important: When a G29 is executed, tool offsets and/or cutter
compensation will be deactivated on the way to the intermediate point and
are re-activated when the axis moves from the intermediate point to the
point indicated in the G29 block.
A G27 causes the control to move the axes at rapid directly to the machine
home position. Only the axes included in the G27 block will be moved.
G27 X__ Y__ Z__ ;
The value entered with the axis name in the G27 block must be the
machine home coordinate for that axis. If it is not, no axis motion will take
place and the control will issue the error message:
“INVALID ENDPOINT IN G27 BLOCK”
Aside from this endpoint check, the only difference between a G27 block
and a G00 block requesting a move to the machine home coordinates is
that the G27 is not modal. If G01, G02 or G03 modes were active before
the G27 was executed, they will be reactivated immediately after the G27
block is completed.
G27 block commands are usually given after tool offset modes have been
cancelled.
14.3.4
Machine Home Return
Check (G27)