FANUC AC SPINDLE MOTOR a series
2. FUNCTION EXPLANATION
B–65160E/02
102
2. Specifying a position gain
Specify an initial value of about 2000 (20 sec
–1
) to 3000 (30
sec
–1
), then adjust the value as needed. Basically, specify
identical values for the spindle and tapping axis.
After specifying the position gain, check whether the spindle is
operating as designed. For that purpose, check that the position
error (value displayed on the CNC screen) during stable rotation
at the maximum speed is almost the same as the theoretical value.
This theoretical value is calculated as shown below. If the
theoretical value is substantially different, re–check the
parameters related to position gain, gear ratio, and detector.
Perr(Nr)[pulse] +
Nr[min
*1
]
60
4096[pulse rev]
1
PG[sec
*1
]
Perr(Nr) [pulse]: Position error in stable rotation at Nr
Nr [min
–1
] : Maximum speed in rigid tapping
PG [sec
–1
] : Position gain in rigid tapping
If the gear ratio is 1:1 at
Nr = 4000 min
–1
and PG = 3000 (30
sec
–1
), the position error in stable rigid tapping at Nr is calculated
as follows:
Perr(Nr)[pulse] +
4000
60
4096
1
30
+ 9102[pulse]
3. Specifying a velocity loop gain
Specify the maximum velocity loop gain that does not cause the
motor at rest to vibrate. Adjust the velocity loop gain so that the
velocity deviation decreases. During the adjustment, observe the
velocity deviation and motor speed. Sample waveforms before
and after the adjustment are shown below:
(a) Waveform before adjustment
(No. 4044 = 10, No. 4052 = 10)
(b) Waveform after adjustment
(No. 4044 = 20, No. 4052 = 60)
CH1 : Velocity deviation
CH2 : Motor speed
CH1 : Velocity deviation
CH2 : Motor speed