Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 397)

Axis Motion
Chapter 14
14-21
Polar programming allows a programmer to use polar coordinates (using
angles and distance specified with a radius) as a means of establishing the
end point of a move rather then specifying the normal cartesian coordinates
of the end point. G16 and G15 are modal G--codes used to start and stop
polar coordinate programming respectively.
After a G16 block in a part program the control will interpret the axis
words as polar programming commands. Cancel polar programming with
a G15 block in a part program. The G15 program block can not contain
any axis words. Note that the G15 program block can cancel other modal
group 15 functions such as cylindrical interpolation (refer to appendix C
for a complete listing of modal group 15 G--codes).
Axis words in the current plane (selected by G17, G18, and G19) are used
to program angle and radius values. The order in which they are assigned
to a plane in AMP is significant in determining their use.
Specifying the Radius:
The first axis word that is used to describe the current plane is used
to specify radius values. Negative radius designations are measured
180 degrees from the current angle designation.
Specifying the Angle:
The second axis word that is used (to describe the current plane) is
used to specify angle designations. The angle is specified in units of
degrees. Positive angles are measured counter clockwise and
negative angles are measured clockwise.
For example if the current plane is G17 (defined in AMP to be the X, Y
plane) during polar programming:
Any X word in a program is used as a radius value for all following
moves until re-specified using another X word or polar programming
is cancelled with a G15 block.
Any Y word in a program is interpreted to be the angle for all
following moves until re-specified using another Y word or polar
programming is cancelled with a G15 block.
For the purpose of explanation this section assumes that the X,Y plane
(G17) is the currently active plane for all polar programming examples and
figures. Any other axis word that is specified in a polar block and is not in
the current plane is interpreted by the control as a normal cartesian
coordinate value.
14.2
Polar Coordinate
Programming (G15, G16)