Safe Brake Test (Sbt) - Siemens SINUMERIK 840D sl Function Manual

Connecting Sensors/Actuators

7.4 Safe brake test (SBT)

7.4 Safe brake test (SBT)
7.4.1 Field of application
When the drives are powered–down axes and mechanical systems can drop as a
result of gravity. The mechanical braking system test should be used for all axes
which must be prevented from moving in an uncontrolled manner by a holding
brake. This test function is primarily intended for so–called "vertical axes".
The functionality is based on "travel to fixed stop". The travel to fixed stop can be
individually parameterized to test the function of the mechanical braking system. It
is activated and deselected from the PLC. For further details on travel to fixed
stop, see /FB1/, F1.
The machine manufacturer can use his PLC user program to close the brake at a
suitable instant in time (nominal value, every 8h similar to the SI test stop) and initi-
ates the drive to produce an additional force in addition to the weight of the axis. In
a fault–free state, the brake can apply the necessary force, i.e. the axis will hardly
move.
When an error occurs, the actual position value exits the parameterizable monitor-
ing window. In this case, travel to fixed stop is terminated so that the position con-
troller can prevent the axis falling. The brake test is then negatively acknowledged.
The brake test must always be started when the axis is at a standstill (also see
Chapter 7.4.5 "Activation"). The direction in which the drive produces its force is
specified by the PLC using a "traversing motion" via FC 18. The target of this tra-
versing motion must be able to be reached without incurring any potential hazard
for the case that the brake cannot provide the necessary force.
7.4.2 Parameter assignment
The user can use the following axial NCK machine data to parameterize the func-
tion test of the mechanical braking system:
for 840D sl
MD 37000: $MA_FIXED_STOP_MODE
MD 37030: $MA_FIXED_STOP_THRESHOLD
MD 36966 $MA_SAFE_BRAKETEST_TORQUE
MD 36967: $MA_SAFE_BRAKETEST_POS_TOL
MD 36968: $MA_SAFE_BRAKETEST_CONTROL
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SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) – 05.2008 Edition
© Siemens AG 2008 All Rights Reserved
05.08