HEIDENHAIN ITNC 530 - 6-2010 DIN-ISO PROGRAMMING User Manual page 203

Central angle CCA and arc radius R
The starting and end points on the contour can be connected with four
arcs of the same radius:
Smaller arc: CCA<180°
Enter the radius with a positive sign R>0
Larger arc: CCA>180°
Enter the radius with a negative sign R<0
The direction of rotation determines whether the arc is curving
outward (convex) or curving inward (concave):
Convex: Direction of rotation G02 (with radius compensation G41)
Concave: Direction of rotation G03 (with radius compensation G41)
Example NC blocks
N100 G01 G41 X+40 Y+40 F200 M3 *
N110 G02 X+70 Y+40 R+20 * (ARC 1)
or
N110 G03 X+70 Y+40 R+20 * (ARC 2)
or
N110 G02 X+70 Y+40 R-20 * (ARC 3)
or
N110 G03 X+70 Y+40 R-20 * (ARC 4)
The distance from the starting and end points of the arc
diameter cannot be greater than the diameter of the arc.
The maximum radius that can be entered directly is
99.9999 m, with Q parameter programming 210 m.
You can also enter rotary axes A, B and C.
HEIDENHAIN iTNC 530 203