
11.SPINDLE SPEED FUNCTION B-63943EN-1/02
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11.15 SPINDLE OUTPUT SWITCHING
Overview
Spindle output switching switches between the two motor windings,
one for low speed and the other for high speed, incorporated into the
special spindle motors. This ensures that the spindle motor
demonstrates stable output characteristics over a wide range.
Since spindle output switching is a function of the spindle control unit,
also refer to the manual for the spindle control unit being used.
This section describes the relationship between spindle output
switching and the spindle control function in the CNC.
Explanation
- Operation of output-switchable spindle motor
To switch the spindle output characteristics, the windings are usually
switched using a relay. Prior to the completion of winding switching,
the spindle rotates free from drive power.
Output switching changes the relationship between a speed command,
issued from the CNC to the spindle, and the output characteristics of
the spindle motor. However, the relationship between the speed
command and spindle motor speed is not changed.
- Output switching timing
During actual machining, the spindle is usually controlled in the
following way.
<1> Constant spindle speed during cutting, such as milling
<2> Continuously changing spindle speed during cutting, such as in
constant surface speed control
<3> Controlling the position loop including the spindle motor during
rigid tapping, spindle positioning, Cs contour control, etc.
For applications such as those in (1), we recommend switching the
output characteristics for low speed and high speed by using the
spindle motor speed detection signal of the spindle control unit.
For applications such as those described in (2) and (3), the spindle
must not rotate with no drive power applied during cutting or
positioning. It is necessary for the output characteristics to be
switched appropriately before machining or for output switching to be
masked by using a PMC ladder sequence.
- Output switching and gear switching
Spindle output switching ensures that the spindle motor demonstrates
stable characteristics over a wide range, and eliminates the
requirement of a mechanical spindle gear switching mechanism.
In creating a PMC ladder sequence for output switching, however,
using the gear switching of the CNC’s spindle control function may
facilitate programming.
Note the following points when using gear switching for CNC spindle
control for output switching with a machine tool having no
mechanical gear switching mechanism.