Siemens SINUMERIK 840D sl Programming Manual page 209

Supplementary conditions
● Both the starting point and the end point must be outside the area of the basic circle of the
involute (circle with radius CR around the center point specified by I, J, K). If this condition
is not satisfied, an alarm is generated and the program processing is canceled.
● The two options for programming the end point (directly via Cartesian coordinates or
indirectly via the specification of an opening angle) are mutually exclusive. Consequently,
only one of the two programming options may be used in a block.
● If the programmed end point does not lie exactly on the involute defined by the starting point
and basic circle, interpolation takes place between the two involutes defined by the starting
and end points (see following figure).
The maximum deviation of the end point is determined by a machine data (→ machine
manufacturer). If the deviation of the programmed end point in the radial direction is greater
than the value defined by this MD, then an alarm is generated and program processing is
canceled.
NC programming
Programming Manual, 12/2019, 6FC5398-2EP40-0BA0
Fundamentals
2.9 Motion commands
209