34
1019658 11/2014
4.7 Axial Forces at the Wave Generator
When a Harmonic Drive® Gear is used as a speed reducer (torque input via Wave Generator), the deflection of the Flexspline
leads to an axial force acting on the Wave Generator. This axial force acts in the direction of the Flexspline diaphragm.
When the Harmonic Drive® Component Set is used as a speed accelerating gear (reverse operation, e. g. when braking), the
axial force acts in the opposite direction. In any case the axial force must be absorbed by the input shaft (motor shaft).
The Wave Generator thus needs to be fixed on the input shaft in the axial direction. In closed Harmonic Drive® Units
and gearboxes the axial force is absorbed internally.
Ratio
30
F
AX
= 2 ·
T
_
D
· µ · tan 32°
[Equation 34.3]
50
F
AX
= 2 ·
T
_
D
· µ · tan 30° + 2µPF
[Equation 34.4]
80...160
F
AX
= 2 ·
T
_
D
· µ · tan 20° + 2µPF
[Equation 34.5]
Table 34.2
Sizes
14
17
20
25
32
40
50
2µPF [N] for CSD and SHD
2.1
4.1
5.6
9.8
16
24
39
with:
F
AX
= Axial force [N]
D
= (Size) · 0.00254 [m]
T
= Torque at the output [Nm]
µ
= 0.07 Coefficient of friction
2µPF = Additional force (only CSD) [N]
Example
Size 32 (CSD-32-50)
Output torque = 300 Nm
Coefficient of friction µ = 0.07
200 Nm
F
AX
= 2 · (32 · 0.00254) m · 0.07 · tan 30°+16
F
AX
= 215 N
Table 34.6
Illustration 34.1
Speed reducer
Reverse
operation
