YASKAWA SGD7S Product Manual page 471

Problem Possible Cause
The limit switch position and
Improper
dog length are not appropri-
Stop Posi-
ate.
tion for
The overtravel limit switch
Overtravel
position is too close for the
(OT) Signal
coasting distance.
Noise interference occurred
because of incorrect Encoder
Cable specifications.
Noise interference occurred
because the Encoder Cable
is too long.
Noise interference occurred
because the Encoder Cable
is damaged.
Position
The Encoder Cable was sub-
Deviation
jected to excessive noise
(without
interference.
Alarm)
There is variation in the FG
potential because of the
influence of machines on the
Servomotor side, such as a
welder.
There is a SERVOPACK
pulse counting error due to
noise.
The encoder was subjected
to excessive vibration or
shock.
The coupling between the
machine and Servomotor is
not suitable.
12.5 Troubleshooting Based on the Operation and Conditions of the Servomotor
Confirmation
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Check the Encoder Cable
to see if it satisfies speci-
fications. Use shielded
twisted-pair cables or
screened twisted-pair
cables with conductors of
at least 0.12 mm
(stranded wire).
Check the length of the
Encoder Cable.
Check the Encoder Cable
to see if it is pinched or
the sheath is damaged.
Check to see if the
Encoder Cable is bundled
with a high-current line or
installed near a high-cur-
rent line.
Check to see if the
machines are correctly
grounded.
Check to see if there is
noise interference on the
I/O signal line from the
encoder or Serial Con-
verter Unit.
Check to see if vibration
from the machine
occurred.
Check the Servomotor
installation (mounting sur-
face precision, securing
state, and alignment).
Check the linear encoder
installation (mounting sur-
face precision and secur-
ing method).
Check to see if position
offset occurs at the cou-
pling between machine
and Servomotor.
Continued from previous page.
Correction
Install the limit switch at
the appropriate posi-
tion.
Install the overtravel
limit switch at the
appropriate position.
Use cables that satisfy
the specifications.
2
• 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.
Replace the Encoder
Cable and correct the
cable installation envi-
ronment.
Correct the cable lay-
out so that no surge is
applied by high-current
lines.
Properly ground the
machines to separate
them from the FG of
the encoder.
Implement counter-
measures against noise
for the encoder wiring
or Serial Converter Unit
wiring.
Reduce machine vibra-
tion. Improve the
mounting state of the
Servomotor or linear
encoder.
Correctly secure the
coupling between the
machine and Servomo-
tor.
Continued on next page.
Reference
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12
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12-65