
B-65280EN/05 FANUC AC SPINDLE MOTOR αi series 2.EXPLANATION OF OPERATION MODES
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2.5.9 Number of Error Pulses in Spindle Synchronous Control
This subsection describes the method of calculating the number of
error pulses (position error) of each spindle on spindle synchronous
control mode, and also describes the items to be checked when a
calculated value differs from the actual number of error pulses.
(1) Calculating the number of error pulses on spindle synchronous control
When the spindle is rotating at a constant speed, the number of error
pulses is calculated as follows:
)(secgainPosition
1
(sec)60
)(minspeedationsynchronizSpindle
)rev/pulse(4096
)pulse(pulseserrorofNumber
1
1
−
−
×
×
Example :
When spindle synchronous speed = 1000 min
-1
, and position gain
= 20 sec
-1
(pulse) 3413.
20
1
60
1000
4096 ApproxpulseserrorofNumber =××=
(2) Checking the number of error pulses on spindle synchronous control
If the number of error pulses on spindle synchronous control checked
by diagnosis (diagnosis screen) differs greatly from the calculated
value, check the following:
(a) Spindle speed (This can be checked using the actual rotation
speed indication of the CNC.)
(b) Motor speed indication on the spindle monitor screen or the
spindle check board
(c) Actual gear ratio between the spindle and motor found from the
spindle speed and motor speed checked by (a) and (b)
(d) Spindle-to-motor gear ratio parameters (Nos. 4056 to 4059)
(e) Position gain parameters (Nos. 4065 to 4068)
(f) How the gear selection signals (CTH1A, CTH2A) are used for
selection (This item can be checked on the spindle motor screen
or the PMC signal status screen.)
NOTE
When the 1/100 unit is set as the gear ratio setting
resolution (with bit 1 of No. 4006 set to 0), the actual
number of error pulses may differ from the
calculated value by several pulses due to the
fraction of the gear ratio.
In such a case, the difference between the actual
number of error pulses and the calculated value can
be decreased when the 1/1000 unit is set as the
gear ratio setting resolution (with bit 1 of No. 4006
set to 1).