Siemens SINUMERIK 840Di sl Programming Manual page 350

Tool offsets
8.8 Tool radius compensation (G40, G41, G42)
Note
A negative offset value is the same as a change of offset side (G41, G42).
You can generate equidistant paths with OFFN, e.g., for rough-finishing.
Working plane G17 toG19
From this information, the control detects the plane and therefore the axis directions for
compensation.
Example of milling cutters
N10 G17 G41 ...
The tool radius compensation is performed in the X/Y plane, the tool length compensation is
performed in the Z direction.
Note
On 2-axis machines, the tool radius compensation is only possible in "real" planes, in
general with G18 (see tool length compensation table).
Tool length compensation
The wear parameter assigned to the diameter axis on tool selection can be defined as the
diameter value (MD). This assignment is not automatically altered when the plane is
subsequently changed.
350
Programming Manual, 11/2006, 6FC5398-1BP10-2BA0
Fundamentals