Siemens SINUMERIK 840D sl Function Manual page 158

A3: Axis Monitoring, Protection Zones
3.3 Protection zones
the MCS. Therefore, when monitoring the software limit switches, the machine position at the
time when CALCPOSI() is executed is used to resolve the ambiguity in such cases.
Note
Preprocessing stop
When using CALCPOSI() in conjunction with transformations, it is the sole responsibility of
the user to program a preprocessing stop (STOPRE) with the preprocessing before
CALCPOSI() for the synchronization of the machine axis positions.
Protection zone clearance and conventional protection zones
With conventional protection zones, there is no guarantee that the safety clearance set in
<Limit>[3] is maintained for all protection zones during a traversing movement on the
specified path. It is only guaranteed that no protection zone will be violated when the end point
returned in <Dist> is extended by the safety clearance in the traversing direction. However,
the straight line can pass very close to a protection zone.
Protection zone clearance and collision avoidance protection zones
With collision avoidance protection zones, there is a guarantee that the safety clearance set
in <Limit>[3] is maintained for all protection zones during a traversing movement on the
specified path.
The safety clearance specified in <Limit>[3] only takes effect when the following applies:
<Limit>[3] > (MD10619 $MN_COLLISION_TOLERANCE)
If bit 4 is set in <TestLim> (see above) (value 16) (calculation of the further direction), then
the direction vector received in _MOVDIST is only valid when the hundred thousands digit is
set in the function return value (status). If such a direction cannot be determined because either
protection zones have been violated or a transformation is active, the input value in _MOVDIST
remains unchanged, no further error message is issued.
References
● Further information on working area limitation can be found in:
Programming Manual, Fundamentals
Section "Supplementary commands" > "Working area limitation"
● Further information on software limit switches can be found in:
Function Manual, Basic Functions; (A3) Axis monitoring, protection zones,
Section "Axis monitoring" > "Limit switch monitoring"
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Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Basic Functions