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7 Troubleshooting
MITSUBISHI CNC
7.3.5 Troubleshooting the Spindle System When There Is No Alarm or Warning
If an abnormality is observed in the spindle system but no alarm or warning has occurred, refer to the following table and
check the state.
[1] The rotation speed command and actual rotation speed do not match.
[2] The acceleration/deceleration time is long or has increased in length.
[3] The motor stops during cutting.
[4] The vibration and noise (gear noise), etc., are large.
[5] The spindle coasts during deceleration.
Investigation item Investigation results Remedies
1
Check the commanded speed and the spindle
rotation speed displayed on the drive monitor
screen.
The speed command is not input correctly. Input the correct speed command.
The speed command is correct. Check the investigation item No. 2.
2
Check whether there is slipping between the
motor and spindle. (When connected with a
belt or clutch.)
There is slipping. Repair the machine side.
No particular problems found. Check the investigation item No. 3.
3
Check the spindle parameters (SP026, SP129
and following).
The correct values are not set. Set the correct values.
The correct values are set. Replace the spindle drive unit.
Investigation item Investigation results Remedies
1
Check whether the friction torque or load
inertia has increased.
The friction torque has increased. Repair the machine side.
No particular problems found. Check the investigation item No. 2.
2
Check if there is any abnormality in the motor's
rotation during coasting.
The bearings do not rotate smoothly. Replace the spindle motor.
The bearings rotate smoothly. Check the investigation item No. 3.
3
Check whether the torque limit signal has been
input.
The signal has been input. Release the input signal.
The signal is not input. Replace the drive unit.
Investigation item Investigation results Remedies
1
Check the load rate (load meter value) during
cutting.
The load meter sways over 120% during
cutting.
Reduce the cutting amount.
No particular problems found. Check the investigation item No. 2.
2 Carry out the same investigations and remedies as section (4).
Investigation item Investigation results Remedies
1
Check the machine's dynamic balance. (Coast
from the maximum speed.)
The same noise is heard during coasting. Repair the machine side.
No particular problems found. Check the investigation item No. 2.
2
Check whether there is a resonance point in
the machine. (Coast from the maximum
speed.)
Vibration and noise increase at a set rotation
speed during coasting.
Repair the machine side.
No particular problems found. Check the investigation item No. 3.
3 Check the machine's backlash.
The backlash is great. Repair the machine side.
No particular problems found. Check the investigation item No. 4.
4
Change the setting of the speed loop
parameter (SP005:VGN1).
The vibration and noise are lost when the
setting value is lowered by approx.100.
Change to the setting value.
(Note) The impact response will drop.
The symptoms do not change even if the
above value is set.
Return the setting values to the original
values.
Check the investigation item No. 5.
5
Jiggle the encoder connectors (drive unit side
and encoder side) and check if they are
disconnected.
The connection is loosened. Correctly connect the connector.
The connector fixing is normal. Check the investigation item No. 6.
6
Turn the power OFF, and check the connection
of the speed encoder cable with a tester.
The connection is faulty or disconnected.
Replace the encoder cable.
Correct the connection.
The connection is normal. Replace the drive unit.
Investigation item Investigation results Remedies
1
When connected with a belt or clutch, check
whether there is slipping between the motor
and spindle.
There is slipping. Check the machine side and repair it.
No particular problems found. Replace the drive unit.