Siemens Sinumerik 840D sl Programming Manual page 253

Machining direction (G41/G42)
From this information, the control detects the direction in which the tool path is to be displaced.
Note
A negative offset value has the same significance as a change of offset side (G41 ↔ G42).
Working plane (G17/G18/G19)
From this information, the control detects the plane and therefore the axis directions for
compensation.
Example: Milling tool
Program code
...
N10 G17 G41 ...
...
Note
On 2-axis machines, tool radius compensation is only possible in "real" planes, usually with
G18.
Tool length offset
The wear parameter assigned to the diameter axis on tool selection can be defined as the
diameter value using an MD. This assignment is not automatically altered when the plane is
subsequently changed. To do this, the tool must be selected again after the plane has been
changed.
Turning:
Fundamentals
Programming Manual, 01/2015, 6FC5398-1BP40-5BA2
11.1 Tool radius compensation (G40, G41, G42, OFFN)
Comment
; The tool radius compensation is performed in the X/Y
plane, the tool length offset is performed in the Z di-
rection.
Tool radius compensation
253