Harmonic Drive FHA-Cmini Series, Manual

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2-3 Verifying and examining load weights
Selection guidelines
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2-3 Verifying and examining load weights
The FHA-C mini series actuator incorporates a precise cross roller bearing for directly supporting an
external load (output flange). To demonstrate the full ability of the actuator, verify the maximum load
weight as well as the life and static safety coefficient of the cross roller bearing.
Checking procedure

Checking the maximum load weight (M max , Fr max , Fa max )
Calculate the maximum load weight (M max , Fr max , Fa max )
↓
Check the maximum load weight (M max , Fr max , Fa max ) is less than or equal to the permissible
loads (Mc, Fr, Fa)

Checking the life of the cross roller bearing
Calculate the average radial load (Fr av ) and average axial load (Fa av ).
↓
Calculate the radial load coefficient (X) and the axial load coefficient (Y).
↓
Calculate the life of the bearing and verify the life is allowable.

Verifying the static safety coefficient
Calculate the static equivalent radial load (Po).
↓
Verify the static safety coefficient (fs).
Specifications of the main roller bearing
The following table shows the specifications of the main roller bearings built in FHA-C mini series
actuators.
Table 1
Item
Model
Pitch circle
diameter of
a roller (dp)
Offset
amount (R)
Basic
dynamic
rated load
(C)
Basic static
rated load
(Co)
Permissible
axial load
(Fa)
Permissible
moment
capacity
(Mc)
mm mm N N N N·m
FHA-8C 35 12.9 5800 8000 200 15
FHA-11C 42.5 14 6500 9900 300 40
FHA-14C 54 14 7400 12800 500 75
Maximum load weight
The table below shows how to calculate the maximum load
weight (M max , Fr max , Fa max ).
Confirm that each maximum load weight is less than or equal
to each permissible load.

Formula (1)
M max =Fr max (Lr+R)+Fa max ·La
Symbols used in the formulas
M
max Max. moment capacity N·m(kgf·m)
Fr max Max. radial load N(kgf) See Fig.1.
Fa max
Max. axial load N(kgf) See Fig.1.
Lr ,La
———— mm See Fig.1.
R Offset amount mm
See Fig.1 and
Table 1.
Fr
Fa
La
Lr R
Load
Actuator
dp
Fig. 1: External load action diagram