Siemens SINUMERIK 840D sl Function Manual page 298

Connecting sensors and actuators
8.6 Safe Brake Test (SBT)
For a PLC-controlled axis, also see:
Reference: /FB2/, P2 "Autonomous single-axis processes"
Note
The signals shown here are only intended for diagnostics and providing an understanding. The
signals should not be influenced by the user program elsewhere.
Sequence to test the mechanical braking
Before the brake test can be started via FB 11 (from the basic program), the NC axis to be
tested must be transferred to the PLC as "PLC-controlled axis". During the complete test, the
axis must remain a PLC-controlled axis. Start via FB11 can be made after the transfer to the
PLC.
The start parameter of FB11 must be continuously 1 during the complete test. With MD36968
$MA_SAFE_BRAKETEST_CONTROL bit 0 =1, shortly before the brake is closed, the actual
holding torque is determined and is temporarily used in the drive as average value for the
torque limiting. After the brake is closed, the PLC-controlled axis is traversed in the specified
direction against the brake using FC18. If the fixed stop is detected ("Fixed stop reached" DB31-
DB61, DBX62.5), the PLC interrupts the traversing motion (FC18 is exited with error 30). The
reduced torque limits are withdrawn and the brake is re-opened.
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Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Safety Integrated