
2.EXPLANATION OF OPERATION MODES FANUC BUILT-IN SPINDLE MOTOR Bis series B-65280EN/05
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(3) Adjustment procedure
(3)-1 Specifying an acceleration/deceleration time constant (1):
Specifying a provisional value
Before optimizing the acceleration/deceleration time constant, adjust
the gain to improve the response. Following (a) or (b) below, specify a
provisional acceleration/deceleration time constant according to the
target maximum speed.
(a) Specifying a provisional time constant according to the velocity waveform in
actual acceleration/deceleration
Observe the motor velocity waveform (velocity control mode) in
acceleration up to the maximum rigid tapping speed. Specify such a
provisional time constant that the inclination (acceleration) during
rigid tapping acceleration becomes about a half of the inclination of a
tangent to the motor velocity waveform near the location of maximum
speed. See the sample waveform shown below.
Nr: Maximum rigid tapping speed (No. 5241 to 5244)
4000 min
-1
in this example
ta: Time of acceleration by the maximum torque at Nr
About 400 ms in this example
tr: Rigid tapping acceleration/deceleration time constant
(No. 5261 to 5264) 800 ms, which is two times ta, in
this example
N
ta
Motor speed
4096 min
-1
/ 5V
In this example, the maximum rigid tapping speed Nr is set to 4000
min
-1
. To determine the acceleration/deceleration time constant, the
motor velocity waveform in acceleration up to 4000 min
-1
is observed.
If the acceleration is performed with the maximum motor torque at
4000 min
-1
, the acceleration time ta needed to attain 4000 min
-1
is
about 400 ms, as shown above. This is the minimum value of
acceleration/deceleration time constant tr, which can be specified
without consideration of cutting load. A time constant that can be
specified in consideration of cutting load is usually about 1.2 to 1.5
times this value. As a provisional value for gain adjustment,
approximately double (800 ms) is specified here.