Siemens SINUMERIK 840D sl Function Manual page 293

MD36968 $MA_SAFE_BRAKETEST_CONTROL, bit 0: Sequence check for the brake test
Principally, the automatic determination of the load torque available using MD36968
$MA_SAFE_BRAKETEST_CONTROL, bit 0 = 1 is preferred. This is because over the
complete traversing path of a suspended axis the torque situation continually changes to some
extent or the other. The torque situation is, e.g. dependent on the different tools/workpieces
being used, and can vary significantly. Using the automatic torque determination function, the
instantaneous holding torque available at standstill is automatically determined (m
temporarily used as average value for the torque limiting in the drive. In this case, it must be
ensured that at the start of the test, the brake is open, otherwise an incorrect reference value
will be determined. With the automatic torque determination function, the plausibility of the
load torque is not checked. The currently available holding torque is displayed in r1509 "Force
setpoint before force limiting".
If the automatic torque determination function is not used (MD36968
$MA_SAFE_BRAKETEST_CONTROL, bit 0 = 0), then p1532 "Torque limit offset" should be
parameterized. Also in this case, when selecting the brake test, the holding torque required
for the force due to the weight is internally measured and the effective brake test torque
adapted. Contrary to the automatic torque determination function, the plausibility of the load
torque is checked.
MD36968 $MA_SAFE_BRAKETEST_CONTROL, bit 1: Criterion for reaching the torque limit
The brake test sequence requires that during the programmed traversing distance, the torque
limit is reliably reached (MD36968 $MA_SAFE_BRAKETEST_CONTROL, bit 1 = 0).
If the programmed traversing distance is very short, e.g. as a result of restricted space for the
axis to move, then it can occur that the required limit value is not reached in the short time that
the axis moves (Alarm 20096 "Axis %1 Brake test aborted, additional information %2").
Using MD36968 $MA_SAFE_BRAKETEST_CONTROL, bit 1 = 1, reaching the programmed
end position is no longer used as criterion for aborting the test. This means that using its
monitoring timer, the PLC itself can decide the wait time until the torque limit is reached. The
test can be continued if, during this time, DB31-61.DBX62.5 is set = 1. If the torque limit is not
reached, the PLC exits the brake test with DB31-61.DBX11.0 = 0.
MD36968 $MA_SAFE_BRAKETEST_CONTROL, Bit 2: Positioning response at the end of the
SINAMICS brake test
The positioning behavior at the end of the SINAMICS brake test must be set so that the brake
is subject to a minimum load. By pressing against the brake, the axis moves away from the
last programmable position. To conclude the brake test, the actual axis position for the next
path motion is used. (MD36968 $MA_SAFE_BRAKETEST_CONTROL bit 2 = 0). This results
in motion to the last programmed axis position on the path.
By setting MD36968 $MA_SAFE_BRAKETEST_CONTROL bit 2 = 1, the actual axis position
is not accepted. After the axis has been pressed against the brake, the closed-loop position
controller withdraws the axis to the last programmed position.
Vertical axes can be prevented from sagging as a result of a repeated brake test by setting
$MA_SAFE_BRAKETEST_CONTROL bit 2 = 1. It is also possible to briefly exceed the
software limit switch while pressing against the brake without initiating an alarm.
Safety Integrated
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Connecting sensors and actuators
8.6 Safe Brake Test (SBT)
) and is
Act
293