REXROTH IndraDyn A Series, Project Planning Manual

Page: 185 / 220

Rexroth IndraDyn A Application Notes
9-29
9.15 Bearing Lifetime
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
10h
= 30,000 operating hours
(calculated according to ISO 281, ed. 1993.01)
This applies to all IndraDyn motors based on the following:
•
The permitted loads from the corresponding chapter 9.13 "Shaft load"
are never exceeded.
•
The motor is operated within the permitted operating conditions and
within the permitted ambient temperature range of 0° C to +40° C.
•
The „mean speed“ over the entire processing cycle conforms to the
following characteristics for the grease lifetime, whereby the following
applies:
( )
h 30000 t m m
f
n n
<
n
m
: mean speed
n
m(tf)
: mean speed for which a grease lifetime of 30,000 h can be
expected.
Fig. 9-33: Mean speed
Differing loads can have the following influences:
•
Premature malfunction of the bearing due to increased deterioration or
mechanical damage.
•
Reduction of the grease lifetime, leading to premature bearing loss.
⇒
Avoid exceeding the load limits.
In other cases, the bearing lifetime is reduced as follows:
3000
F
F
L
3
ist _ radial
radial
h 10
⋅




=
L
10h
: (Bearing lifetime according to ISO 281, ed. 12/1990)
F
radial
: Permissible radial force in N (Newton)
F
radial_ist
: Actual radial force in N (Newton)
Fig. 9-34: Calculation of the bearing lifetime L
10h
if the permissible radial force
F
radial
is exceeded
Note:
Under no circumstances may the actually acting radial force
F
radial_ist
be higher than the maximum permissible radial force
F
radial_max
.
Mechanical Lifetime of Bearings
Mechanical Lifetime with
Increased Radial Force