Siemens SINUMERIK 840D sl Function Manual page 97

The actual values are synchronized in the crosswise data comparison clock cycle. Actual value
synchronization is also performed when a crosswise data comparison of the SI actual position
outputs an error.
Actual values are also synchronized after "referencing" and for "parking axis".
The currently determined and the maximum SI speed difference since the last reset are
displayed in the axis-specific service screen for diagnostic purposes.
To define the slip tolerance, the maximum differential speed is set in MD36949
$MA_SAFE_SLIP_VELO_TOL. As a result of an action, such as e.g. maximum acceleration
when starting, gearbox stage changes with oscillation, a situation is created where the actual
values drift apart. This value can be taken as nominal value from the diagnostics screen
"Maximum velocity difference", multiplied by a factor of 1.5 and then entered into MD36949.
Note
Actual values are only synchronized when there is an actual value difference between the two
channels of 2 mm or 2 m degrees in each SI monitoring clock cycle.
Supplementary conditions
The two SI actual positions no longer display the correct absolute machine position. The correct
position can now only be read out via the NC actual position.
The safety monitoring functions SG, SBH, SBR and "n<n
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
initiates an alarm in the channel in which this speed violation was detected. The associated
stop response is therefore still initiated through two channels.
SGA "n<n
Note
It is not possible to activate the safe SE and SN functions for an axis/spindle where slip can
occur between the motor and the load.
Activation
The actual value synchronization is selected by setting bit 3 in machine data 36901
$MA_SAFE_FUNCTION_ENABLE or parameter p9501 "SI Motion enable safety functions".
In addition, SI function "SBH/SG monitoring" must also be enabled.
Actual value synchronization is only permissible if a monitoring function with absolute reference
has not been simultaneously enabled. If SE and/or SN are also selected, power on Alarms
27033 and F01688 are also output when booting.
The actual value synchronization is only permissible for 2-encoder systems. If this function is
enabled for a single-encoder system, Alarm 27033/F01688 is output.
Safety Integrated
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Basics regarding the safety functions integrated in the system/drive
" can also assume different static states in the two monitoring channels.
x
6.4 Actual value conditioning
" still only respond to actual value
x
97