Rockwell Automation 8520-GUM 9/Series CNC Grinder Operation and Programming Manual Documentation Set - Manual (Page 451)

Axis Motion
Chapter 12
12-79
There are two types of mirroring:
programmable mirror image
This is activated through programming a G50.1 and G51.1
manual mirror image
This is activated through PAL or the {FRONT PANEL} softkey
Programmable Mirror Image (G50.1, G51.1)
Use the programmable mirror image feature to mirror (duplicate yet
reversed) axis motion commands about some defined plane. Activate this
feature using the G51.1 code and cancel it using the G50.1 code.
Mirroring takes place about the axis position specified in the G51.1 code.
The format for the G51.1 code is:
G51.1X__ Z__ ;
The axis motion commands in any following blocks are executed with the
motion direction reversed (including incremental moves) as if a mirror
were placed on the programmed point perpendicular to the axis. The
G51.1 code is modal and remains in effect until cancelled by a G50.1.
If only one axis is programmed in the G51.1 block, the mirroring plane is
perpendicular to that axis. If more than one axis is programmed, a mirror
plane is established perpendicular to each. Axis moves is mirrored relative
to the mirror point defined for each axis.
Important: The control only mirrors those axes that are programmed in
the G51.1 block. Axes not programmed in the G51.1 block execute
normally.
A G50.1 block cancels the mirror image function.
G50.1X__ Z__ ;
The control cancels the mirror feature only for those axes that are
programmed in the G50.1 block. Axes not programmed in the G50.1 block
remain mirrored.
It may be necessary to program a numeric value with the axis words in a
G50.1 block to avoid a syntax error (depending on how AMP was
configured by your system installer). In any case, there is no significance
to any numeric values programmed with the axis words. These values are
ignored by the control.
12.11
Mirror Image (G50.1, G51.1)