53
5.5.4 Grease Change
If the strain wave gear is operated at regular operating conditions (average environmental temperatures ≤ 40 °C, average
application loads ≤ rated torque and rated speed), the initial lubrication is sufficient for the lifetime of the gear. Abrasion of
the sliding parts of a strain wave gear is influenced by the grease condition. Grease performance changes by temperature and
deteriorates rapidly as the temperature rises. Therefore a replacement of the grease may become necessary depending on the
operating conditions.
In illustration 53.2, the grease change interval depending on the grease temperature is given. This chart is valid for a gear loaded
with rated torque and rated speed. If the application's average torque is higher than the rated torque, the grease change interval
can be determined with equation 53.3. This means, that for a temperature of Harmonic Drive® Grease SK-1A or SK-2 of 40 °C a
change should take place after approx. 8.5 · 10
8
revolutions of the input shaft.
To change the grease the gear should be completely disassembled and cleaned before regreasing. Fresh grease should be
applied to the inside of the Flexspline, the Wave Generator bearing, the Oldham Coupling and the teeth of the Circular Spline
and Flexspline.
Illustration 53.2
L
GT
= Number of Wave Generator revolutions until grease change
L
GTn
= see diagram
T
N
= Rated torque
T
av
= Average torque of the application
L
GT
= L
GTn
.
(
)
3
T
N
T
av
Equation 53.3
1E+08
1E+09
1E+10
20
40
60
80
100
120
140
Grease Temperature [°C]
1E+10
1E+09
1E+08
Number of W
ave Gener
at
or r
evolutions
20 40 60 80 100 120 140
Flexolub®-A1
4B No.2
SK-1A, SK-2
1021387 12/2018
V02
The required grease quantity is depending on the operating position. If the unit is mainly operated with Wave Generator
above, additional grease must be supplied above the Wave Generator, see illustration 52.3 and table 52.2.
5.5.3 Additional Grease Package
Illustration 53.1
Adapter flange
Motor
If the units are used
mainly with Wave Gene-
rator above, then additi-
onal grease lubrication
is necessary. In this
case about 60 % of the
available space in the
adaptor flange should
be filled with grease.