Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 384)

Axis Motion
Chapter 14
14-8
Example 14.5
Arc Programmed Using + or - Radius
Arc 1
center angle less
than 180 degrees Arc 2
center angle greater
than 180 degrees
G00X15Y30; G00X15Y30;
G90G02X40.Y25.R18.F200; G90G02X40.Y25.R-18.F200;
M30; M30;
Figure 14.5
Results of Arc Programmed Using Radius Example
X
Y
Arc 2
end point
start
point
40
25 Arc 1
R18
+
R--18
If the end point of the arc is not specified, or if the end point is the same as
the start point, do not use R. Only J, I, and K can specify the center point in
these cases.
Important: Any axis in the current plane that is not specified when
programming a circle defaults to the current axis position values. This
results in the end point of an arc having the same coordinate value as the
start point of the arc for that axis.
If I, J, and/or K is used to program the arc center the control will cut a
full circle.
If R is used to program the radius of the arc the control will not move
the axis. This is because the control defines an arc with a 0 degree
center angle.