Harmonic Drive FHA - C mini Series, Manual

Page: 36 / 68

2-3 Verifying and examining load weights
Selection guidelines
2-5
1
2
3
4
5
6
7
8
9
10
11
Apx
Sel
ect
ion gui
del
ines
Dynamic equivalent radial load
Life of cross roller bearing
Calculate the life of cross roller bearing with the formula (7) below:
Cross roller bearing life based on oscillating movement
Use formula (8) to calculate the cross roller bearing life against oscillating movement.
If the oscillating angle is 5° or less, fretting wear may occur because oil film does not form effectively on the
contact surface between the race and rolling element of the cross roller bearing. In such cases, consult HDS.

Formula (7): Cross roller bearing life
10/3
6
10 B
Pc fw
C
N 60
10
L 





⋅
×
×
=
−
av
Symbols used in the formulas
L
B-10
Life hour ―
N
av
Average output
rotational speed
r/min
Obtained by formula
(4).
C
Basic dynamic rated
load
N(kgf) See Table 1.
Pc
Dynamic equivalent
radial load
N(kgf) Obtained by formula
(6).
fw Load coefficient — See Table 3.

Formula (6): Dynamic equivalent radial load
av
av av
av
Fa Y
dp
La) Fa R) (Lr 2(Fr
Fr X Pc ⋅ +





 ⋅ + +
+ ⋅ =
Symbols used in the formulas
Pc
Dynamic equivalent
radial load
N(kgf)
Fr av Average radial load N(kgf) Obtained by formula (2).
Fa av Average axial load N(kgf) Obtained by formula (3).
dp
Pitch circle diameter of
a roller
mm See Table 1.
X Radial load coefficient — See Table 2.
Y Axial load coefficient — See Table 2.
Lr, La — mm See Fig.1.
R Offset amount mm See Fig.1 and Table 1.
Table 3 Load coefficient
Loaded state fw
Smooth operation free
from impact/vibration
1 to 1.2
Normal operation 1.2 to 1.5
Operation subject to
impact/vibration
1.5 to 3

Formula (8): Cross roller bearing life (oscillating)
10/3
6
Pc fw
C 90
n 60
10
Loc
1






⋅
×
θ
×
×
=
Symbols used in the formulas
Loc Life hour ―
n
1
Number of reciprocating
oscillation per min.
cpm ―
C
Basic dynamic rated
load
N(kgf) See Table 1.
Pc
Dynamic equivalent
radial load
N(kgf) Obtained by formula
(6).
fw Load coefficient ― See Table 3.
θ Oscillating angle/2 ― See Fig.3.
Oscillating angle
θ
Fig. 3: Oscillating movement