Rockwell Automation 8520-GUM 9/Series CNC Grinder Operation and Programming Manual Documentation Set - Manual (Page 326)

Coordinate Control
Chapter 11
11-10
The external offset allows all work coordinate system zero points to be
shifted simultaneously relative to the machine coordinate system. This
offset can compensate for part positioning shifts that result when a
different chuck or mandrel is installed.
Also, use the external offset to match the work coordinate systems on
mechanically different machines. The machines can then use the same
part program with the same G54-G59.3 coordinate values. This allows
part programs to be less machine dependent.
Figure 11.8
External Offsets
G54
G54
G56
G56
X
X
X
X
Z
Z
Z
Z
Work coordinate systems
prior to external offset
Work coordinate systems
after activating external offset of
X.7 Z-3.4
Machine coordinate
system zero point
X+4.0
Z-6.5
X+3.3
Z-3.1
X+4.1
Z+1.1
X+3.4
Z+4.5
12174-I
Important: Once an external offset is entered into the coordinate offset
table, it cannot be canceled. This offset remains active even after power
has been turned off. It becomes a permanent part of all work coordinate
systems including the default work coordinate system (unless “none” is
selected as the default coordinate system).
11.3
Work Coordinate System
External Offset