2.HOW TO USE SERVO MOTORS SPECIFICATIONS FOR THE βiS SERIES B-65302EN/01
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2.3.4 Machine Movement per 1 Revolution of Motor Shaft
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.
• The machine movement per 1 revolution of motor shaft 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.
• 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.
• 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.
• 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.