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

Connecting sensors and actuators

8.6 Safe Brake Test (SBT)

In order to be able to exchange single-channel SI-specific signals between the NCK and PLC
in a dedicated data area, a corresponding communication interface exists between these
components. The meaning of the individual bits in this interface are defined by the user.
NCK
$A_PLCSIOUT[1...96]
$A_PLCSIIN[1...96]
Supplementary conditions
System variables $A_PLCSIOUT[1...96] and $A_PLCSIIN[1...96] are protected so that they
cannot be accessed from other programs, except the NCK-SPL program (SAFE.SPF). A
corresponding programming command is rejected with Alarm 17070 "Channel %1 block %2
Data write-protected".
8.6 Safe Brake Test (SBT)
8.6.1

Applications

Axes and mechanical systems can drop due to gravity when the drives are switched off. The
function test of the brake mechanical system should be used for all axes that must be prevented
from moving in an uncontrolled manner by a holding brake. This test function is primarily
intended for vertical axes.
The functionality is based on "travel to fixed stop" (FXS). 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 (guide value, every 8 h, see Chapter "Information sheets from the various
regulatory bodies (Page 30)") and to initiate that the drive produces an additional force in
addition to the weight of the axis. As long as no fault has occurred, the brake can exert the
necessary braking torque / the necessary braking force and the axis will hardly move.
When an error occurs, the actual position value exits the parameterizable monitoring window.
This prevents an axis from sagging. The function test of the brake mechanical system is
negatively acknowledged.
The brake test must always be started when the axis is at a standstill. The direction in which
the drive exerts its torque / its force is defined by the PLC using a "traversing motion" via FC18.
The direction of travel should be selected so that the motor applies force in the direction of the
already force already exerted due to the weight of the load. It must be possible to reach the
target of this motion without any danger (no collision, sufficient distance to the end stops) if
the brake cannot provide the necessary torque / force.
Note
When the brake test is active, no temperature compensation may be carried out.
290
PLC
DB18.DBB128-131,
DB18.DBB432-439
DB18.DBB132-135,
DB18.DBB440-447
96 bits from the NCK to PLC
96 bits from the PLC to NCK
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Safety Integrated