12.4  Troubleshooting Based on the Operation and Conditions of the Servomotor
12-55
Abnormal 
Noise from 
Servomotor
The Servomotor vibrated 
considerably while perform-
ing the tuning-less function 
with the default settings.
Check the waveform of 
the motor speed.
Reduce the load so 
that the moment of 
inertia ratio or mass 
ratio is within the allow-
able value, or increase 
the load level or reduce 
the rigidity level in the 
tuning-less level set-
tings.
page 8-11
The machine mounting is not 
secure.
Check to see if there are 
any loose mounting 
screws.
Tighten the mounting 
screws.
–
The machine mounting is not 
secure.
Check to see if there is 
misalignment in the cou-
pling.
Align the coupling.
–
Check to see if the cou-
pling is balanced.
Balance the coupling.
–
The bearings are defective.
Check for noise and 
vibration around the bear-
ings.
Replace the Servomo-
tor.
–
There is a vibration source at 
the driven machine.
Check for any foreign 
matter, damage, or defor-
mation in the machine’s 
moving parts.
Consult with the 
machine manufacturer.
–
Noise interference occurred 
because of incorrect I/O sig-
nal cable specifications.
Check the I/O signal 
cables to see if they sat-
isfy specifications. Use 
shielded twisted-pair wire 
cables or screened 
twisted-pair cables with 
conductors of at least 
0.12 mm
2
.
Use cables that satisfy 
the specifications.
–
Noise interference occurred 
because an I/O signal cable 
is too long.
Check the lengths of the 
I/O signal cables.
The I/O signal cables 
must be no longer than 
3 m.
–
Noise interference occurred 
because of incorrect Encoder 
Cable specifications.
Make sure that the rotary 
or Linear Encoder Cable 
satisfies the specifica-
tions. Use a shielded 
twisted-pair wire cable or 
a screened twisted-pair 
cable with a conductors 
of at least 0.12 mm
2
.
Use cables that satisfy 
the specifications.
–
Noise interference occurred 
because the Encoder Cable 
is too long.
Check the length of the 
Encoder Cable.
• Rotary Servomotors: 
The Encoder Cable 
length must be 50 m 
max.
• Linear Servomotors: 
Make sure that the 
Serial Converter Unit 
cable is no longer 
than 20 m and that 
the Linear Encoder 
Cable and the Sensor 
Cable are no longer 
than 15 m each.
–
Noise interference occurred 
because the Encoder Cable 
is damaged.
Check the Encoder Cable 
to see if it is pinched or 
the sheath is damaged.
Replace the Encoder 
Cable and correct the 
cable installation envi-
ronment.
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Continued from previous page.
Problem Possible Cause Confirmation Correction Reference