
B-65262EN/03 SPECIFICATIONS FOR THE αiS/αi SERIES 2.HOW TO USE SERVO MOTORS
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Direct connection using a rigid coupling
Direct connection using a rigid coupling has the following advantages
over direct connection using a flexible coupling:
• More economical
• The coupling rigidity can be increased.
• If the rigidity is the same as with a flexible coupling, the inertia
can be reduced.
However, this method has the following disadvantages:
• The motor shaft and the ball screw must not slide from each
other in the radial direction, and the angle of the motor shaft to
the ball screw must be fixed.
For this reason, a rigid coupling needs to be mounted very carefully.
It is desirable that the run-out of the ball screw is 0.01 mm or less.
When a rigid coupling is used on the motor shaft, the run-out of the
hole for the ball screw must be set to 0.01 mm or less by adjusting the
tightness of the span ring.
The run-out of the motor shaft and the ball screw in the radial
direction can be adjusted or compensated to a certain extent by
deflection. Note, however, that it is difficult to adjust or measure
changes in the angle. Therefore, the structure of the machine should
be such that precision can be fully guaranteed.
Gears
This method is used when the motor cannot be put in line with the
ball screw because of the mechanical interference problem or when
the reduction gear is required in order to obtain large torque. The
following attention should be paid to the gear coupling method:
• Grinding finish should be given to the gear, and eccentricity,
pitch error, tooth-shape deviations etc. should be reduced as
much as possible. Please use the JIS, First Class as a reference of
precision.
• Adjustment of backlash should be carefully performed.
Generally, if there is too little backlash, a high-pitched noise will
occur during high-speed operation, and if the backlash is too big,
a drumming sound of the tooth surfaces will occur during
acceleration/deceleration. Since these noises are sensitive to the
amount of backlash, the structure should be so that adjustment of
backlash is possible at construction time.