Rockwell Automation 8520-GUM 9/Series CNC Grinder Operation and Programming Manual Documentation Set - Manual (Page 453)

Axis Motion
Chapter 12
12-81
When the mirror image function is active on only one of a pair of axes, the
control:
executes a reverse of programmed G02/G03 arcs. G02 becomes
counter-clockwise and G03 becomes clockwise.
activates a reverse of programmed G41/G42 compensation. G41
becomes compensation right and G42 becomes compensation left.
Manual Mirror Image
In addition to the programmable mirror image feature, the control can also
be equipped with an optional mirror image switch, installed by your
system installer, that activates the manual mirror image feature. This
feature can also be activated using the {FRONT PANEL} softkey with the
appropriate PAL programming.
The manual mirror image feature differs from the programmable mirror
image feature in that when using manual mirror image the location of the
mirrored plane is fixed along the selected axis in the current work
coordinate system. This means that the mirror plane is parallel to the
selected axis and also passes through the zero point of the currently active
work coordinate system.
The mirrored plane is fixed and cannot be moved from along the selected
axis. This mirrored plane is the equivalent of programming a
programmable mirror image and using all zero values for the axis words.
Your system installer has the option to install a switch for each of the
available axes. What axes are mirrored with what switches depend on the
PAL program for your system. You can mirror about more than one axis
using more than one manual mirror image switch at the same time or one
switch can control more than one axis. Refer to documentation prepared
by your system installer for details.
Important: You can use programmable mirror image at the same time as
manual mirror image. When this is done the coordinates for the
programmable mirror image are calculated first followed by the manual
mirror image.