Bearing Lifetime - Bosch Rexroth IndraDyn A Series Project Planning Manual

9-32
Application Notes

9.15 Bearing Lifetime

Mechanical service life of
bearings
Mechanical bearing lifetime with
increased radial force
The bearing lifetime is an important criterion for the availability of
IndraDyn motors. When the lifetime is considered, the "mechanical
lifetime" of bearing components and materials is differentiated from the
"grease lifetime" of the bearing lubricant.
If IndraDyn motors are operated within the limits specified for radial and
axial loads, the mechanical service life of the bearings is as follows:
L = 30,000 operating hours
10h
(calculated according to ISO 281, ed. 1993.01)
This applies to all IndraDyn motors based on the following:
• The permitted load of the motor from chapter 9.13 "Shaft Load" is
never exceeded.
• The motor is operated under the permitted conditions for use and in
the permitted ambient temperature range of 0° C to +40° C.
• The "mean speed" driven over the entire processing cycle conforms
with the characteristic curves for the grease lifetime, whereby
n : mean speed
m
n : mean speed for which a grease lifetime of 30,000 h can be
m(tf)
expected.
Fig. 9-40: Mean speed
Differing loads can have the following effects:
• Premature failure of the bearing due to increased wear or mechanical
damage.
• Reduction of the grease lifetime, leading to premature failure of the
bearing.
⇒ Avoid exceeding the load limits.
In other cases, the bearing lifetime is reduced as follows:
L
10
L : (Bearing lifetime according to ISO 281, ed. 12/1990)
10h
F : Determined permissible radial force in N (Newtons)
radial
F : Actually acting radial force in N (Newtons)
radial_act
Fig. 9-41: Calculation of the bearing service life L
force F is exceeded
radial
Note: Under no circumstances may the actually acting radial force
F be higher than the maximum permissible radial force
radial_act
F .
radial_max
<
n n
=
m m(t 30000 h)
f
3
 
F
 
= ⋅
radial
30000
 
h
F
 
radial _ ist
if the permissible radial
10h
DOK-MOTOR*-MAD/MAF****-PR03-EN-P
Rexroth IndraDyn A