
3.SAFETY FUNCTIONS B-63494EN/02
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3.3 STOP
3.3.1 Stopping the Spindle Motor
Because the spindle motor is an induction type motor, power-down
during rotation causes the motor to continue rotating for a certain
amount of time. From a safety standpoint, the motor may have to be
stopped immediately. If the CNC detects an error and judges that the
spindle can be controlled, it waits until the rotation of the spindle
stops, then shuts off the power. This wait period can be specified as a
safety parameter. For this safety parameter, two different values can
be specified. One value is used when the safety function is active (the
door is open), and the other value is used otherwise. The values must
be determined in consideration of the stop period calculated from the
spindle speed.
To implement the function, the CNC CPU and monitor CPU
individually incorporate a timer function. Normal operation of the two
CPUs are mutually checked to ensure the safety of the timers.
To speed down and stop the spindle, the PMC must input the spindle
emergency stop signals (*ESPA(G71.1), *ESPB(G75.1), and so on).
When this signal is input, the spindle slows down and stops. (A
Ladder program for inputting this signal in case of alarm must be
created.) The emergency stop input (connector CX4) of the PSM has
the same effect. If the emergency stop signal is connected to
emergency stop input (connector CX4) of the PSM, the spindle slows
down and stops in the emergency stop state.
If this processing is not performed, power-down causes the spindle
motor to continue rotating at the speed prior to power-down (and
eventually stopping in the end).
CAUTION
The CNC outputs a DO notifying of an alarm. If
necessary, the spindle should be stopped. Because
the DO output is not duplicated, this DO may not be
output when a single failure is detected. In that
case, the speed cannot be reduced, but the MCC is
finally shut off and brought into the safe stop state.
If a spindle amplifier alarm or any other state in
which the spindle motor cannot be controlled is
encountered, immediate power-down is carried out.