JUKI AP-874/IP-420, Instruction Manual

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Phenomenon Cause Corrective measure
4. The tread slips off the
needle upon being
trimmed.
① The returning force of the thread
take-up spring is too high.
② The tension of the tension controller
No. 1 is too high.
③ The counter knife is improperly posi-
tioned.
○ Refer to "I-4-7. Thread take-up
spring" p.19 .
○ Refer to "III-1-4. Positioning
the counter knife and the knife
thread guide" p.107
.
5. The needle thread
cannot be trimmed.
(The bobbin thread
can be trimmed.)
① The last stitch has been skipped.
(The clearance between the needle
and the hook is too large.)
○ Refer to "III-1-2. Needle and hook
adjustment" p.105 .
6. Bobbin thread cannot
be trimmed.
(Needle thread can be
trimmed.)
① The moving knife fails to catch the
bobbin thread at the last stitch.
(The stitching pitch of the last stitch
is excessively large, and the bobbin
thread is not present on the moving
knife locus.)
○ Decrease the stitching pitch of the
last stitch. (To approximately 2
mm)
7. Neither the needle
thread nor the bobbin
thread can be trimmed.
① The thread trimming timing is wrong.
②
The knife has been damaged.
③ The knife pressure is inadequate.
④
The moving amount of the moving
knife is too short.
⑤
Pattern input failure
○ Replace the knife.
○
Increase the knife pressure.
○
It is necessary to check the thread
trimming motor operation.
○
Input the pattern prior to thread
trimming using the forward stitch.
8. Thread cannot be
trimmed sharply
①
Thread trimming timing is wrong.
② The knife pressure is too low.
③
The knife blade is blunt.
○
Refer to "III-1-4. Positioning
the counter knife and the knife
thread guide" p.107
.
○ Increase the knife pressure.
○
Replace the knife.
9. The machine cannot
be powered on.
①
Emergency switch is in the ON
state.
○
Refer to
"I-5. Emergency stop
switch" p.23 .