Siemens SINUMERIK 840DE Programming Manual page 148

Programming Motion Commands
4.13 Involute interpolation (INVCW, INVCCW)
Options 1. and 2. are mutually exclusive. Only one of these notations may be used each
block.
Further information
There are further options when the angle of rotation is programmed with AR. Two different
involutes can be implemented (see diagram) by specifying the radius and center point of the
base circle as well as the start point and direction of rotation (INVCW/INVCCW). The
selected path must be defined unambiguously by the sign of the angle.
The two involutes defined by the start point and the base circle are shown in the diagram
above. In this case, end point 1 is approached when AR > 0 is programmed and end point 2
when AR < 0 is programmed.
Accuracy
If the programmed end point does not lie exactly on the involute defined by the start point
and base circle, interpolation takes place between the two involutes defined by the start or
end point (see diagram). The maximum deviation of the end point is determined by a
machine data. If the programmed end point deviates more in the radial direction than the MD
setting, an alarm is generated and the program run aborted.
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Programming Manual, 10.2004 Edition, 6FC5 298-7AB00-0BP1
Fundamentals