JUKI DU-1181N Manuel D'utilisation page 92

24. TROUBLES IN SEWING AND CORRECTIVE MEASURES
Trouble
1. Stitch skipping
2. Thread breakage
3. Loose stitches
(Isolated idling loops)
4. Faulty feed
(Multi-layered parts
of the material cannot
be fed smoothly /
puckering)
Cause
1 The machine head has not been
properly threaded.
2 The hook has scratches.
3 The timing between the needle and
hook is too early or too late.
4 The clearance between the needle
and the hook point is too large.
5 The pressure of the presser foot is
too low.
6 The needle number selected is
improper.
1 The hook has scratches.
2 The returning force of the thread
take-up spring is insuffi cient.
3 The timing between the needle and
hook is too early or too late.
4 The needle thread tension is
excessive.
5 The needle comes in contact with the
hook point.
6 The clearance between the needle
and the hook point is too large.
7 Faulty adjustment of the needle
thread take-up eyelet.
8 The needle number selected is
improper.
1 The thread has not been passed
through the notch of the bobbin case
tension spring.
2 he thread path is poorly fi nished.
3 The bobbin does not rotate smoothly. ™ Replace the bobbin or the bobbin
4 he bobbin thread tension is too high. ™ Decrease the bobbin thread
5 The bobbin thread tension is too low. ™ Increase the bobbin thread tension.
6 An untwisted synthtic thread is used. ™ Slightly lower the sewing speed.
7 The needle number selected is
improper.
1 Faulty adjustment of the longitudinal
position of the presser foot.
2 Feed dog height is not enough.
3 Feed dog height is excessive.
™ Refer to "10. Thread the machine
heads".
™ Remove the scratches on the hook
point using a fi ne emery paper.
™ Refer to "17. Needle-to-hook
relationship".
™ Refer to "17. Needle-to-hook
relationship".
™ Tighten the pressure regulator.
™ Replace the needle with one which
is one count thicker.
™ Remove the scratches on the hook
point using a fi ne emery paper.
™ Decrease the tension and increase
the stroke of the thread take-up
spring.
™ Refer to "17. Needle-to-hook
relationship".
™ Adjust the needle thread tension
properly.
™ Refer to "17. Needle-to-hook
relationship".
™ Refer to "17. Needle-to-hook
relationship".
™ Refer to "21. Adjusting the thread
take-up stroke".
™ Replace the needle with one which
is one count thicker.
™ Properly thread the bobbin case.
™ Grind it using a fi ne emery paper or
buff it up.
case.
tension.
(1,800 sti/min)
™ Replace the needle with one which
is one count thicker.
™ Refer to "18. Adjusting the walking
foot and the presser foot".
™ Refer to "14. Height of the feed
dog".
™ Refer to "14. Height of the feed
dog".
– 52 –
Corrective measure