Siemens SINUMERIK 840Di sl Programming Manual page 352

Tool offsets
8.8 Tool radius compensation (G40, G41, G42)
Intersection
Select intersection with SD 42496: CUTCOM_CLSD_CONT
FALSE:
If two intersections appear on the inside when offsetting an (virtually) closed contour, which
consists of two circle blocks following on from one another, or from one circle block and one
linear block, the intersection positioned closest to the end of block on the first partial contour
is selected, in accordance with standard procedure.
A contour is deemed to be (virtually) closed if the distance between the starting point of the
first block and the end point of the second block is less than 10% of the effective
compensation radius, but not more than 1000 path increments (equals 1 mm with three
decimal places).
TRUE:
In the same situation as described above, the intersection positioned on the first partial
contour closer to the block start is selected.
Changing the direction of compensation
G41/G42, G42/G41 can be programmed without an intermediate G40.
Changing the working plane
It is not possible to change the working plane G17 to G19 when G41/G42 is active.
352
G41
G42
Programming Manual, 11/2006, 6FC5398-1BP10-2BA0
Fundamentals