
3. INSTRUCTIONS
B–65142E/04
DESCRIPTIONS FOR THE α series
26
The machine movement per 1 revolution of motor shaft must be
determined at the first stage of machine design referring the load torque,
load inertia, rapid traverse speed, and relation between minimum
increment and resolution of the position sensor mounted on the motor
shaft. To determine this amount, the following conditions should be taken
into consideration.
D The machine movement per 1 revolution of motor shaft (“L”) must be
such that the desired rapid traverse speed can be obtained. For
example, if the maximum motor speed is 1500 min
–1
and the rapid
traverse speed must be 12 m/min., the amount of “L” must be 8
mm/rev. or higher.
D As the machine movement per 1 revolution of motor shaft is reduced,
both the load torque and the load inertia reflected to motor shaft also
decrease.
Therefore, to obtain large thrust, the amount of “L” should be the
lowest value at which the desired rapid traverse speed can be obtained.
D Assuming that the accuracy of the reduction gear is ideal, it is
advantageous to make the machine movement per 1 rev. of motor shaft
as low as possible to obtain the highest accuracy in mechanical servo
operations. In addition, minimizing the machine movement per 1 rev.
of motor shaft can increase the servo rigidity as seen from the
machine’s side, which can contribute to system accuracy and
minimize the influence of external load changes.
D When the machine is operation is characterized by repeated
acceleration/deceleration cycles, a heating problem may occur due to
the current flow caused by the acceleration and deceleration. Should
this occur, the machine travel distance per motor shaft revolution
should be modified. Given optimum conditions, the machine travel
distance per motor shaft revolution is set such that the motor’s rotor
inertia equals the load inertia based on motor shaft conversion. For
machines such as punch presses and PCB drilling machines, the
machine’s travel distance per motor shaft revolution should be set so
as to satisfy this optimum condition as far as possible, while also
considering the rapid traverse rate and increment system.
3.2
MACHINE
MOVEMENT PER 1
REVOLUTION OF
MOTOR SHAFT