Filter
Top Products
Appendix 2. Selection
A2 - 10
Linear movement load inertia: J
T
The inertia is calculated when a standard workpiece, tool, etc., is attached. The conversion to the
motor shaft by the deceleration ratio is included in the movement amount per motor rotation. Refer
to section "Appendix 2-5 Expressions for load inertia calculation".
J
T = W
.
(
S
20
)
2
= (500 + 10)
.
(
10 2
20
3
)
2
= 5.7 (kg
.
cm
2
)
Load inertia: J
L
This is the sum of the total rotation load inertia and the linear movement load inertia.
J
L = 26.5 + 5.7 = 32.2 (kg
.
cm
2
)
When looking at the load inertia components, the linear movement mass tends to increase.
However, the rotation load generally accounts for most of the inertia. The load inertia does not
change much even if the workpiece mass changes greatly in the table axis.
(2) Obtaining unbalance torque
The unbalance torque is obtained from the moving object mass. Here, the drive system efficiency is
calculated as 1.
Refer to section "Appendix 2-4 Motor shaft conversion load torque".
T
U =
(W
1
W
2
) · g · S
2
10
3
·
=
(510 0) 9.8 10 2
2
10
3
1 3
= 5.3 (N
.
m)
(3) Obtaining friction torque
The friction torque is obtained from the moving object mass and friction coefficient. Here, the drive
system efficiency is calculated as 1. Refer to section "Appendix 2-4 Motor shaft conversion load
torque".
T
F =
F · S
2
10
3
·
=
· W · g · S
2
10
3
·
=
0.05 510 9.8 10 2
2
10
3
1 3
= 0.27 (N
.
m)
(4) Selecting the appropriate motor from the load inertia ratio
Confirm that the motor speed is 3000r/min based on the rapid traverse rate and gear ratio, and
make sure that it is less than the maximum speed. Motor brakes must be provided, so select a
motor from the HFB Series. Note that even when the motor has brakes, the motor inertia for
motors without brakes is used to judge the load inertia ratio.
The motor is judged as appropriate if the capacity is HF103 or more and the load inertia is within
3-fold of the recommended load inertia ratio.
Motor type
Motor inertia
(kg
.
cm
2
)
Load inertia
(kg
.
cm
2
)
Load inertia
magnification
Judgment
HF53 6.1 32.2 5.29
HF103 11.9 32.2 2.71
HF153 17.8 32.2 1.81
HF203 38.3 32.2 0.84
HF353 75.0 32.2 0.43