B–63172EN/01
26. SAFETY FUNCTIONS
NC FUNCTION
163
Shutting off the servo amplifier power causes a dynamic brake to be
applied to the servo motor. Even when a dynamic brake is applied,
however, a servo motor attached to a vertical axis can move under the
force of gravity. To overcome this problem, use a servo motor with a
brake.
While the spindle motor is running, shutting off the motor–driving power
to the spindle amplifier allows the spindle motor to continue running
under its own inertia, which is quite dangerous. When the emergency stop
signal (*ESP) contact opens, it is necessary to confirm that the spindle
motor has been decelerated to a stop, before the spindle motor power is
shut off.
The FANUC servo amplifier α/β series products are designed to satisfy
the above requirements. The emergency stop signal should be input to the
power supply module (called the PSM) for α series. The PSM outputs
a motor power MCC control signal, which can be used to switch the power
applied to the power supply module on and off.
For the servo amplifier β series, input an emergency stop signal to the
servo amplifier, and control the turn–on/off of the motor power using an
external circuit.
The Power Mate i is designed to detect overtravel by using a software
limit function. Normally, no hardware limit switch is required to detect
overtravel. If the machine goes beyond a software limit because of a servo
feedback failure, however, it is necessary to provide a stroke end limit
switch, connected so that the emergency stop signal can be used to stop
the machine.
Fig. 26.1.3 shows an example showing how to use the emergency stop
signal with this Power Mate i and α series servo amplifier.
26.1.3
Servo/Spindle