Specifications

Design Ver. 0002 DS - 1
DS. DESIGN
DS.1 AXIS MOTOR AND SERVO DRIVE SELECTION
DS.1.1 FIRST MOTOR PRE-SELECTION
The motor must meet the specifications
on Torque (Nm), speed, duty cycles or
other kind of requirements of the axis to
be moved. An axis may be like this:
Calculation of the necessary Motor Torque (M)
The total motor torque necessary has two components,
the Continuous Torque M
S
(to maintain the table at a constant speed or fixed in a position),
and the Acceleration Torque M
A
(to change its speed).
The reduction in the Motor ballscrew transmission ( i ) is a factor to be considered in many of
the following calculations.
The Continuous Torque M
S
is due to:
the friction between table with its ways and with the ballscrew M
F
,
to the weight of the table when not moving horizontally M
W
,
and to the cutting force of the tool M
C
.
Friction torque M
F
:
M
F
is the torque due to friction and is given in Nm.
m is the table mass in Kg. d is the diameter of the ballscrew in mm
g is the gravitational acceleration 9.81 m/s
2
h is the ballscrew pitch in meters per turn.
µ is the friction coefficient between the table and the ways it moves on:
Typical
µ values depending on material: Iron 0.1÷0.2
Turcite 0.05
Roller bearings 0.01÷0.02
()
MMM M M M
T S A TOTAL CONTINUOUS ACCELERATION
=+⇒ = +
i
DP
DP
=
1
2
() ( )
()
MM M
i
mg h d
i
F
F TABLE F BALLSCREW
=+ ×=
×××
+
æ
è
ç
ö
ø
÷
×
1
210
1m
p
()
MMMM M M M M
S F W c CONTINUOUS FRICTION WEIGHT CUTTING
=++Þ = + +