Siemens SINUMERIK 840D sl Function Manual page 37

Accuracy
If the programmed end point does not lie exactly on the involute defined by the starting point,
interpolation takes place between the two involutes defined by the starting and end points
(see illustration below).
The maximum deviation of the end point is determined by the machine data:
MD21015 $MC_INVOLUTE_RADIUS_DELTA(end point monitoring for involute)
Figure 2-7
Basic logic functions: Various NC/PLC interface signals and functions (A2)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
MD21015 specifies the max. permissible deviation
Detailed description
2.2 Functions
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