Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 388)

Axis Motion
Chapter 14
14-12
A rotary axis is a non-linear axis that typically rotates about a fixed point.
A rotary axis is not the same as a spindle which uses an M19 to orient to a
specific angle. A rotary axis is a fully positionable axis that is capable of
interpolated motion when programmed in a block with other axes.
The system installer determines which axes are rotary axes in AMP, and
determines the address that is used to command those axes. This manual
assumes that the C--word is used to program a rotary axis. Refer to the
system installer’s documentation for the rotary axis words used in a
specific system.
A rotary axis is programmed in units of degrees. This manual assumes that
the system installer has configured the rotary axis to “rollover” at 359.99
degrees. Rollover means that after the rotary axis exceeds 359.99 degrees
of rotation, its position displays rollover to 0 degrees and starts increasing.
If the axis rotates to a position less than 0 degrees its position displays
rollover to 359.99 degrees and starts decreasing.
Typically a rotary axis is programmed in a block by itself or with linear
moves (rapid G00 or cutting G01 moves). If necessary it is possible,
however, to program a rotary axis in a block that contains circular moves
(G02 or G03).
Programming in absolute or incremental
Rotary axes may be programmed in absolute or incremental mode.
In absolute mode (G90) the rotary axis is programmed to angular positions.
These positions are programmed between 0 and 359.99 degrees. The sign
given to this angular position determines the direction that the rotary axis
will travel to reach the programmed angle. For example programming:
G90C25;
in a part program will cause the rotary axis C, to rotate to an angle of 25
degrees (referenced from a position 0 determined by the system installer).
It will rotate in the positive direction to reach this position. Programming:
G90C-25;
in a part program will cause the rotary axis C, to rotate to the same position
(25 degrees) except that it will rotate in the negative direction to reach this
position.
14.1.5
Positioning Rotary Axes