Siemens Sinumerik 840D sl Function Manual page 172

Safety functions integrated in the system/drive
6.7 Safe software limit switches (SE)
Preconditions
The following prerequisites must be fulfilled for the "safe software limit switches"
function:
S The "safe software limit switches" function must be enabled
S The axis/axes must have been safely referenced (user agreement)
S SGE "SE selection" must be supplied (configured) in both channels
Warning
!
"Safe software limit switches" are only effective if the user agreement has been
given.
During the time in which the measuring system of the machine axis is switched off,
it is not permissible that the axis is mechanically moved. Otherwise this results in
an offset between the last buffered actual position and the real actual position of
the machine axis. This would lead to an incorrect synchronization of the measuring
system resulting in danger to personnel and machine.
If axis motion cannot be prevented mechanically in the shutdown state, either an
absolute encoder must be used or the axis must be referenced again with
reference point approach after switching on.
6.7.1 Effects when an SE responds
Warning
!
The SE function does not predictively monitor the SW (software) limit switches.
This means that the axis stops after passing the limit position. The distance
traveled after the SE is dependent on:
-- How the function was parameterized (monitoring clock cycle, stop response,
...)
-- The actual speed
-- The design of the axis
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SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) - - 10.2015 Edition
© Siemens AG 2015 All Rights Reserved
10/15