Fagor DDS Series Hardware Manual page 204

  Selection criteria
5.
224
DDS
HARDWARE
Ref.1912
· 204 ·
Third motor pre-selection
Calculation of the acceleration torque and time
The required acceleration torque is determined by the total inertia to be
moved and the needed acceleration.
The required acceleration is determined by the acceleration time t
is the time estimated for the motor to reach its rated speed from zero rpm.
M
ACCELERACION
n
Rated motor speed .
N
t
The time it takes the motor to go from 0 rpm to the rated speed.
AC
Taking the value of t from the equation:
AC
t J
=
AC TOTAL
Calculation of the needed rms torque Mrms
The third and last motor selection requires a new data, the RMS torque.
M RMS

= M + M + M
F W AC
where:
t
acceleration time.
AC
tp
tool positioning time.
tc
Cutting time in a machine cycle.
The typical values for t , tp and tc in machine tool cycle are:
AC
t C
M
----- - = 0.6
T
t P
----- = 0.4
T
t AC
--------- - 
0
T
Calculation of the motor peak torque Mpeak
The required maximum torque is the sum of the friction, weight and
acceleration torque.
M MAX
For a given acceleration time, we will need specific acceleration torque and
maximum torque. The motor must be able to provide a peak torque equal to
or greater than the calculated maximum torque.

2 n
N
 -------------------
J
=
TOTAL

60 t
AC

2 n N

----------------------------------------------------------------

60 M
ACCELERACION
2 t AC 2 t p
  --------- -    ---- - 
+ M + M + M +
F W F
T T
t t t t
AC P C AC
T
= M F + M W + M AC
which
AC
2 t C
  ----- -
M + M
W C
T
t
t
S