Specifications

Design Ver. 0002 DS - 3
DS.1.2 SECOND MOTOR PRE-SELECTION
Calculation of Inertia (J)
The next step is to calculate the load that the motor has to move when accelerating; that is,
the Moment of Inertia of all the elements it moves. The total inertia J
TOTAL
is due to the load
J
LOAD
and to the rotor of the motor itself J
MOTOR
.
The inertia due to load can be subdivided into that of the table + that of the ballscrew + that of
the system used to compensate for non-horizontal axes + that of the pulley or gear used for
transmission and which turns with the ballscrew "PULLEY1" . All these elements are affected
by the reduction factor " i " as shown by the following equation.
The inertia due to the "pulley" that turns with the motor "PULLEY2" is not affected by the "i"
factor.
Next, each one of the inertias are defined:
The resulting inertias are in Kg.m
2
i, µ ,h, δ are data used before.
L is the ballscrew length in meters. L
1
is the width of pulley-1 in meters.
L
2
is the width of pulley-2 in meters. D
P1
is the diameter of pulley-1in meters.
D
P2
is the diameter of pulley-2 in meters.
α is the material density: 700 Kg/m
3
for iron/steel
2700 Kg/m
3
for aluminum
Jm
h
TABLE
=⋅






2
2
π
J
dL
BALLSCREW
=
⋅⋅⋅
4
32
πα
J
DL
PULLEY
P
1
1
4
1
32
=
⋅⋅⋅
πα
J
DL
PULLEY
P
2
2
4
2
32
=
⋅⋅⋅
πα
J
JJ J J
i
J
LOAD
TABLE BALLSCREW PULLEY COMPENSATION
PULLEY
=
+++
+
1
2
2
JJJ
TOTAL LOAD MOTOR
=+