HEIDENHAIN TNC 620 (340 56x-02) ISO programming - Manual (Page 146)

146 Programming: Tools
5.3 T
ool Compensation
Contouring with radius compensation: G42 and G41
The tool center moves along the contour at a distance equal to the
radius. “Right” or “left” are to be understood as based on the
direction of tool movement along the workpiece contour. See figures.
X
Y
G41
X
Y
G42
G43 The tool moves to the right on the programmed contour
G42 The tool moves to the left on the programmed contour
Between two program blocks with different radius
compensations G43 and G42 you must program at least
one traversing block in the working plane without radius
compensation (that is, with G40).
The TNC does not put radius compensation into effect
until the end of the block in which it is first programmed.
In the first block in which radius compensation is activated
with G42/G41 or canceled with G40 the TNC always
positions the tool perpendicular to the programmed
starting or end position. Position the tool at a sufficient
distance from the first or last contour point to prevent the
possibility of damaging the contour.