Siemens Sinumerik 840D sl Function Manual page 146

Safety functions integrated in the system/drive
6.3 Safe Stops A- -F
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:
S $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.
S $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 switch-
over is activated. This time is used to bridge the time from identifying the stand-
still 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_STAND-
STILL_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_STAND-
STILL_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_STAND-
STILL_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.
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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