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

03.06
7.4

Safe brake test (SBT)

7.4.1

Applications

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 "traversing to a fixed endstop". The traversing to a
fixed endstop can be individually parameterized to test the function of the mechani-
cal braking system. It is activated and de-selected from the PLC. For further details
on traversing to a fixed endstop, 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 monito-
ring window. In this case, traversing to fixed endstop is terminated so that the posi-
tion controller can prevent the axis falling. The brake test is then negatively ac-
knowledged.
The brake test must always be started when the axis is at a standstill (also see
Subsection 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

Parameterization

The user can use the following axial NCK machine data to parameterize the func-
tion test of the mechanical braking system:
with 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
© Siemens AG, 2006. All rights reserved
SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) – 03.2006 Edition
Connecting Sensors/Actuators
7.4 Safe brake test (SBT)
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