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No.
9/10
Page
FANUC LTD
DESCRIPTION DESIGN DATE
EDIT
Prevention of Gravity Axis Drop
at Power Failure
in αi series servo system
B-65282EN/05-03
Add newly S.Hanyu 04.11.22 01
6. How to confirm the effect
It is possible to confirm the effect of the countermeasure of the prevention of the gravity axis
drop by the following method.
(1) Keep the gravity axis stopping, and record the absolute position of the gravity axis.
(2) Turn off the main breaker of the machine to occur the power failure.
(3) Reboot the machine, and confirm whether the gravity axis is prevented dropping or not by
checking the absolute position of the gravity axis.
(Note) The gravity axis drops a little by the backlash of the brake (20µm max. in case of using 10mm/rev
ball screw), even though the countermeasure of prevention of axis drop works perfectly.
Countermeasure in case that the gravity axis drops when the main breaker is turned off.
If the gravity axis drops after the main breaker of machine is turned off, investigate the
causes by observing the following waveform.
(1) The voltage of the brake coil. → Observe the voltage of the both end of the brake coil.
(2) The voltage of the control power supply for the amplifier.
→ Observe pin A1(24V) and pin A2(0V) of the connector CXA2B of the amplifier.
(3) The voltage of the control power supply for the NC.→ Observe the DC24V supplied to
NC.
(4) The AC input voltage. → Observe the AC input voltage by using the insulated probe.
Improve the following items in case that the voltage of the control power supply for NC
and amplifiers drops down before the brake is effective.
Exchange the relay for operating the brake coil to the relay whose reset time is shorter.
Exchange the control power supply to the bigger capacity type to extend the time to
keep the control power supply
The example of the waveform when the prevention of the gravity axis drop works well.
Input power voltage
AC200V
24V
24V
Power failure
(Main breaker off)
30msec
20msec/div
24V
Control power supply for NC
Control power supply for amplifiers
24V
×
90%
100msec
130msec
Brake is effective
Excitation of
Motor OFF
oltage of brake coil
Brake becomes
effective
Excitation of motor is kept.