Harmonic Drive FHA Mini Series, Manual

Page: 25 / 50

Chapter 2 Guidelines for sizing
FHA-mini
25
2-3 Verifying loads
The FHA-C mini actuators include a precise cross roller bearing for directly supporting the load weight.
For optimal performance, verify that the maximum load weight is less than the allowable load and life
and static safety coefficient of the cross roller bearing.
• Verifying procedures:
(1) Verifying the maximum load
Calculate the maximum load (M max , Fr max , Fa max ).
↓
Verify the maximum loads (M max , Fr max , Fa max ) are less than (≤) allowable loads (Mc, Fr, Fa)
(2) Verifying the life of the cross roller bearing
Calculate the average radial load (Fr av ) and the 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.
(3) Verifying the static safety coefficient
Calculate the static equivalent radial load (Po)
↓
Verify the static safety coefficient.
• Specifications of the cross roller bearing
The following table shows the specifications of the cross roller bearings built in FHA-C mini actuators.
Table 1: Specifications of the cross roller bearings
Item
Model
Circular pitch
of roller
(dp)
Offset
(R)
Basic dynamic
load rating
(C)
Basic static
load rating
(Co)
Allowable
axial load
(Fa)
Allowable torsional
moment
(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
• Calculating the maximum load
Calculate the maximum load (M max , Fr max , Fa max ) with
the following formula and verify that they are less than
their allowances.
M max =Fr max (Lr+R)+Fa max •La (1)
Where, the variables of the formula are:
M max : Maximum torsional moment in N•m(kgf ･ m)
Fr max : Maximum radial load in N(kgf); See Fig.1.
Fa max : Maximum axial load in N(kgf); See Fig.1.
Lr, La: Loading point in mm; See Fig.1.
R: Offset: See Fig.1 and Table 1.
Fr
Fa
La
Lr R
Load
Actuator
dp
Fig.1 Loads