Siemens SINUMERIK 840D Description Of Functions page 176

3 Safety-Related Functions
3.11 Encoder mounting arrangements
The two SI actual positions no longer display the correct absolute machine
Limitations
position. The correct position can now only be read out via the NC actual
position.
Safety monitoring functions SG, SBH, SBR, and "n<n
actual value changes from the particular actual value acquisition channel, not to
changes in the actual value resulting from the actual value synchronization. A
single-channel SG violation only triggers an alarm in the channel in which this
speed violation was detected. The related stop response is still triggered in two
channels, as information is exchanged between the two monitoring channels.
SGA "n<n
channels.
Activating Actual value synchronization is selected by setting bit 3 in MD $MA_/
$MD_SAFE_FUNCTION_ENABLE. In addition, SI function "SBH/SG
monitoring" must also be enabled.
Actual value synchronization is only permissible if no monitoring function with
absolute reference is enabled at the same time. If SE and/or SN are also
selected, power ON Alarms 27033 and 301708 are also output during power
up.
Actual value synchronization is therefore only permitted with SBH/SG axes, as
in this case, the absolute position is not necessarily needed. Further, actual
value synchronization is only permitted for two-encoder systems. If this function
is enabled for a single-encoder system, Alarm 27033 is output.
3.11.5 Application: Spindle with two encoders and drive with slip
(SW 5.2 and lower)
General When subject to crosswise data comparison the actual values between the
NCK and drive must lie within an actual value tolerance specified in the MD.
If the tolerance value is violated, STOP F is output.
For the configuration shown in Fig. 3-45 "Motor with a drive subject to slip" the
System behavior
following behavior is manifested:
The SI actual values for the drive and the NCK are each provided from a
separate encoder. Due to the slip produced by the belt drive, the actual value
between the two encoders drifts apart so that the actual value tolerance is
violated with the relevant stop response.
3-176
SINUMERIK 840D/SIMODRIVE 611 digital SINUMERIK Safety Integrated (FBSI) - Edition 11.03
" can also assume statically different states in the two monitoring
x
Note
It is not possible to activate the safe functions SE and SN for an axis/spindle
where slip can occur between the motor and the load.
" still only respond to
x
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11.03