Siemens SINUMERIK 840D sl Function Manual page 133

range. Otherwise, for the subsequent switchover to a Safe Operating Stop, the SBH limits
could be exceeded, which in turn would initiate a STOP B/A response. This situation can then
only by acknowledged by a restarting again.
A setting corresponding to the worst case scenario means that for a stopping operation, e.g.
from a lower velocity to reach standstill, a wait time is incurred until a Safe Operating Stop is
assumed.
In many cases, protective doors can only be opened after the system has switched over to a
Safe Operating Stop; this means wait times for users. Wait times can be reduced by making
the appropriate parameter assignment:
In this case, a switchover is not made to the Safe Operating Stop after the actual transition
time, but as soon as standstill is identified, and a short transition time has elapsed.
The following machine data are used:
● $MA_SAFE_STANDSTILL_VELO_LIMIT
Switchover speed SBH/SG
Velocity limit with which the axis monitoring channel identifies standstill. A delay time is
started, if this velocity limit is fallen below for a stop request or an SG stage switchover.
● $MA_SAFE_STANDSTILL_DELAY
Delay time, switchover to SBH/SG
After this time, for a stop request, a Safe Operating Stop or an SG stage switchover is
activated. This time is used to bridge the time from identifying the standstill velocity down
to actual standstill.
It should be noted that time $MA_SAFE_STANDSTILL_DELAY only becomes active at the
instant that standstill is actually identified (v < $MA_SAFE_STANDSTILL_VELO_LIMIT) the
remaining time from starting the stop request up to switching over to SBH or the lower SG
stage (stopping delay time) is greater than the value in this machine data (delay time,
switchover to SBH/SG).
If the stop request sequence (with respect to time) has progressed so that the originally started
stopping delay time already expires before $MA_SAFE_STANDSTILL_DELAY expires, then
the originally initiated operation is exited unchanged. This therefore ensures that the
switchover to SBH occurs at the latest after the stopping delay time.
Activation:
The function is active if a value > 0.0 is entered in MD37920
$MA_SAFE_STANDSTILL_VELO_LIMIT.
Supplementary conditions:
When switching over from SG to SBH using SGE "deselect Safe Operating Stop", the function
can only operate if a setpoint velocity limit is activated using MD36933
$MA_SAFE_DES_VELO_LIMIT.
Even when switching over from "non-safety operation" (neither SG nor SBH active) to SBH,
the function cannot be used because a delay time has not been defined for this switchover
operation - and the switchover to SBH is realized without delay.
Safety Integrated
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Safety functions integrated in the system/drive
7.3 Safe Stops A-F
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