10 Inspection, Maintenance, and Troubleshooting
10.1.6 Troubleshooting for Malfunction without Alarm Display
10-18
Absolute
Encoder
Position
Difference
Error
(The position
saved in host
controller
when the
power turned
OFF is dif-
ferent from
the position
when the
power turned
ON.)
Noise interference due to improper
encoder cable specifications
Check if the cable meets recommended
specification.
Use encoder cable with the specified specifications.
Noise interference because the
encoder cable distance is too long.
The wiring distance must be 20 m max.
The encoder cable distance must be within the specified
range.
Noise interference due to damaged
encoder cable
Noise interference occurred to the signal
line because the encoder cable is bent or its
sheath damaged.
Correct the encoder cable layout.
Excessive noise to the encoder cable
Check if the encoder cable is bundled with a
high-current line.
Change the encoder cable layout so that no surge is
applied.
FG electrical potential varies by
influence of such machines on the
servomotor side as welder.
Check if the machine is correctly grounded.
Ground the machine separately from PG side FG.
SERVOPACK pulse counting error
due to noise interference
Check if the signal line from the encoder
receives influence from noise interference.
Take measures against noise for encoder wiring.
Excessive vibration and shock to the
encoder
Vibration from machine occurred or servo-
motor mounting such as mounting surface
precision, fixing, and alignment is incor-
rect.
Reduce vibration from machine or mount securely the
servomotor.
Encoder fault
−
Replace the servomotor.
SERVOPACK fault
Check the multiturn data from SERVO-
PACK.
Replace the SERVOPACK.
Host controller multiturn data read-
ing error
Check the error detection at the host con-
troller.
Correct the error detection section of host controller.
Check if the host controller executes data
parity check.
Execute the multiturn data parity check.
Check noise on the signal line between
SERVOPACK and the host controller.
Overtravel
(OT)
(Movement
over the zone
specified by
the host con-
troller)
An overtravel signal is output (P-OT
(CN1-42) or N-OT (CN1-43)) is at
H.
Check if the voltage of input signal external
power supply (+24 V) is correct.
Connect to the ex24 V power supply.
Check if the overtravel limit switch (SW)
operates properly.
Correct the overtravel limit SW.
Check if the overtravel limit switch (SW) is
connected correctly.
Correct the overtravel limit SW wiring.
The overtravel signal does not oper-
ate normally (P-OT or N-OT signal
sometimes changes).
Check the fluctuation of the input signal
external power supply (+24 V) voltage.
Stabilize the ex24 V power supply voltage.
Check if the overtravel limit switch (SW)
activate correctly.
Adjust the overtravel limit SW so that it operates cor-
rectly.
Check if the overtravel limit switch wiring
is correct. (check for damaged cables, etc.)
Correct the overtravel limit SW wiring.
Incorrect P-OT/N-OT signal selec-
tion
Check the P-OT signal selection (Pn50A.3).
Correct the setting of P-OT signal selection (Pn50A.3).
Check the N-OT signal selection
(Pn50B.0).
Correct the setting of N-OT signal selection (Pn50B.0).
Incorrect servomotor stop method
selection
Check if “coast to stop” in servo OFF status
is selected.
Check Pn001.0 and Pn001.1.
Check if “coast to stop” in torque control
mode is selected.
Check Pn001.0 and Pn001.1.
Improper overtravel position setting
The distance to the position of OT (over-
travel) is too short considering the coasting
distance.
Correct the OT position.
Improper encoder cable specifica-
tions
Check if the cable meets the recommended
specifications.
Use encoder cable with the specified specifications.
Noise interference because the
encoder cable distance is too long.
The wiring distance must be 20 m max.
The encoder cable distance must be within the specified
range.
Noise influence due to damaged
encoder cable
Check if the encoder cable is bent or its
sheath is damaged.
Correct the encoder cable layout.
Excessive noise interference to
encoder cable
Check if the encoder cable is bundled with a
high-current line.
Change the encoder cable layout so that no surge is
applied.
FG electrical potential varies by
influence of such machines on the
servomotor side as welders.
Check if the machine is correctly grounded.
Ground the machine separately from PG side FG.
SERVOPACK pulse count error due
to noise
Check if the signal line from the encoder is
influenced by noise.
Take a measure against noise for the encoder wiring.
Table 10.7 Troubleshooting for Malfunction without Alarm Display (cont’d)
Symptom
Cause
Inspection
Corrective Actions
: Turn OFF the servo system before executing operations.
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