Siemens SINUMERIK 840D sl Function Manual page 226
Sinumerik safety integrated
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Connecting Sensors/Actuators
7.4 Safe brake test (SBT)
Incorrect parameterization in MD $MA_SAFE_BRAKETEST_TORQUE or drive
parameter p1532 could mean that the drive with reduced torque cannot even apply
the required holding torque. This parameterization is detected when the brake test
is selected and results in Alarm 20095 (see Section 10.2). The fact that the actual
torque/force setpoint is displayed in parameter p1509 makes it easier to correctly
parameterize drive parameter p1532. If only the force due to the weight is effec-
tive, then this value can be directly transferred into the drive parameter. This value
must be entered – with an additional safety margin – into MD $MA_SAFE_BRA-
KETEST_TORQUE. The magnitude of the safety margin is orientated to the maxi-
mum holding force of the brake to be tested.
$MA_SAFE_BRAKETEST_CONTROL
Some machines have braked axes whose load torque can very significantly over
the complete traversing range or depending on the workpiece or tool being used. If
drive parameter p1532 cannot be generally parameterized, for all of the situations
using MD 1192, an automatic determination of the load torque present at the start
of the braking test can be activated using MD 36968 $MA_SAFE_BRAKET-
EST_CONTROL. If bit 0 of $MA_SAFE_BRAKETEST_CONTROL is set to 1, then
the torque, determined at the start of the brake test (mAct from Fig. 7-21 or
Fig. 7-22) is temporarily used as average value for the torque limiting in the drive.
The user must carefully ensure that the brake is not previously closed thus pre-
venting an incorrect load torque being determined. This would then mean that the
brake test would be carried-out with an incorrect torque. The plausibility of the load
torque is then no longer checked.
This is the reason that this should only be activated if it is not possible to sensibly
parameterize MD 1532.
$MA_SAFE_BRAKETEST_POS_TOL
The monitoring window for the maximum permissible movement during the brake
test is defined in the axial MD $MA_SAFE_BRAKETEST_POS_TOL. The PLC
actively monitors this position window – from the start of the brake test and not
only when it has been detected that the fixed endstop has been reached. This is a
difference when compared to activating the traversing to the fixed endstop function
from the part program.
$MA_FIXED_STOP_THRESHOLD
The contour deviation that is determined is always used in the brake test to detect
that the fixed endstop has been reached. The parameterization in $MA_FI-
XED_STOP_BY_SENSOR is therefore irrelevant. The required threshold value
must be set in MD $MA_FIXED_STOP_THRESHOLD. This means that the tra-
versing distance from the PLC via FC 18 must be greater than this threshold value.
Furthermore, the drive must have reached its torque limit parameterized using
$MA_SAFE_BRAKETEST_TORQUE.
7-226
SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) – 03.2006 Edition
© Siemens AG, 2006. All rights reserved
03.06
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