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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
4-2. Parameter setting
Set the parameter for Brake control function.
(1) Brake control function enable/disable bit (BRKC)
Set “1”: The brake control function is enabled.
(2) Brake control timer
Set the value which is more than “operate time of brake” (about 100msec).
(3) Setting the emergency stop timer built into the αi amplifier (ESPTM1, ESPTM0)
Set the value which is more than setting of the brake control timer
Parameter number
CNC BRKC Brake control timer ESPTM1 ESPTM0
FS15i
No.1883 #6 No.1976 No.1750 #6 No.1750 #5
FS16i, 18i, 21i,
30i, 31i, 32i, 0i
No.2005 #6 No.2083 No.2210 #6 No.2210 #5
Parameter (Example) 1 100 0 1
Refer to Parameter manual FANUC AC SERVO MOTOR αi series (B-65270EN).
(Note) In case that the multiaxis amplifier (a two-axis amplifiers or a three-axis amplifiers) is used for
the gravity axis, the parameter above need to be set in the same way for the those axes.
5. Cautions
(1) There is possibility that the gravity axis dropping cannot be prevented when the power
failure occurs during heavy cutting, because DC link low voltage alarm occurs before the
brake is effective. To prevent the gravity axis dropping even though the power failure occurs
during heavy cutting, Power Failure Backup Module and Sub Module C are needed.
(2) The gravity axis drops a little by the backlash of the brake (20µm max. in case of using
10mm/rev ball screw), even though this countermeasure of prevention of axis drop works
perfectly. There is a method to brake after pulling up the gravity axis to prevent the gravity
axis dropping by the backlash after power failure by using “Lifting Function Against Gravity
at Emergency Stop”. Set the parameter of “Lifting Function Against Gravity at Emergency
Stop” and operate the emergency stop by the relay whose contact opens at power failure.
(Note) Refer to Parameter manual FANUC AC SERVO MOTOR αi series (B-65270EN).
(3) There is possibility that the gravity axis dropping cannot be prevented when the input
voltage drops gradually at power failure, because the contact of the relay to operate the
brake is delayed to open. It is possible to improve the gravity axis dropping by using the
relay whose contact becomes off at as high voltage as possible, or using the power failure
detector made by the third party (*).
(*1) Example: S87A made by OMRON.
(4) There is possibility that the gravity axis dropping cannot be prevented in case that one phase
is open where the relay for the power failure detection is not connected. To prevent the
gravity axis dropping even though open phase, connect the three relays to all of “line to line”,
and connect the contact of each relay in series to detect the open phase.