
B–63833EN–1/02
9. SPINDLE SPEED FUNCTION
601
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.
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.
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.
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 (see 9.3) 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.
9.13
SPINDLE OUTPUT
SWITCHING
General
Operation of
output–switchable
spindle motor
Output switching timing
Output switching and
gear switching