Normal operation
In normal operation, using the holding brake for clamping (holding) an axis in
standstill, the "static holding torque" (M4) – static friction (friction coefficient
μ
H
) specified in the data sheets takes effect.
Failure (E-Stop)
In the case of failure (E-Stop), where the holding brake is used to decelerate
a moving axis, the "dynamic braking torque" – sliding friction (friction coeffi‐
cient μ
G
) applies.
The dynamic braking torque is lower than the indicated static holding torque
M4. It is approx. 0.75 … 0.8 x M4. Therefore, observe the following descrip‐
tion of dynamic sizing.
Dynamic sizing
The load torque has to be lower than the minimum dynamic torque which the
brake can provide. Otherwise, the dynamic brake torque is not sufficient to
stop the axis.
If a mass is to be decelerated in a defined time or over a defined distance,
the mass inertia of the whole system additionally has to be taken into ac‐
count.
Other important aspects for sizing
The holding brake is not a safety brake (cf. DIN EN 954 / 03.97 and Informa‐
tion Sheet for vertical axes published by the institution for statutory accident
insurance and prevention ["Süddeutsche Metall-Berufsgenossenschaft"]).
Due to uncontrollable disturbances, such as film rust on the brake friction sur‐
face, the holding brake torque can be reduced. Additionally, overvoltage and
too high temperatures can weaken the permanent magnets and the brake.
Sizing - Recommendation
Considering these factors, the following recommendation can be given for
sizing holding brakes at axes:
The holding torque required for the application should not exceed a maximum
of 60% of the static holding torque (M4) of the holding brake used.
Holding torque reduction and premature wear
occur when braking moving axes!
NOTICE
Do not use the holding brake to stop a moving axis during normal operation.
This is allowed for E-Stop situations only. In this situation, the specified rated
torque of the holding brake (M4) is reduced to the dynamic braking torque.
Complete deterioration of the holding brake can be expected after approx.
20,000 revolutions of the brake when applied.
Observe the commissioning instructions for holding brakes. See also Func‐
tional Description of firmware (index entry "Motor holding brake → Operating
behavior").
7.3.5
Mechanical attachment of driving elements
General information
For all attachments of driving elements to the output shaft (e.g., gears, cou‐
plings, pinions), the following instructions absolutely have to be observed.
Redundant bearings
Generally, redundant bearings are to be avoided by all means when attach‐
ing driving elements. The tolerances inevitably present in such cases will lead
to additional forces acting on the bearing of the motor shaft and, should the
occasion arise, to a distinctly reduced service life of the bearing.
If redundant attachment cannot be avoided, it is absolutely neces‐
sary that you consult Rexroth.
Bosch Rexroth AG
DOK-INDRV*-KCU02+KSM02-PR03-EN-P
232/337
Rexroth IndraDrive Mi Drive Systems with KCU02 KSM02, KMS02/03, KMV03, KNK03
Notes on project planning
LSA Control S.L. www.lsa-control.com [email protected] (+34) 960 62 43 01