24. Troubles In Sewing And Corrective Measures - JUKI PLC-1690 Manuel D'utilisation

24. TROUBLES IN SEWING AND CORRECTIVE MEASURES

Troubles
1 Thread path, needle point, hook blade
1. Thread breakage
(Thread frays or
worn out.)
2 Needle thread tension is too high.
3 Bobbin case opening lever provides an
4 Needle comes in contact with the blade
5 Amount of oil in the hook is too small.
6 Needle thread tension is too low.
(Needle thread
7 Thread take-up spring works excessively
trails 2 to 3 cm
from the wrong
8 Timing between the needle and the hook
side of the fabric.)
1 Timing between the needle and the hook
2. Stitch skipping
2 Pressure of the presser foot is too low.
3 The clearance provided between the top
4 Hook needle guard is not functional.
5 Improper type of needle is used.
1 Bobbin thread does not pass through the
3. Loose stitches
2 Thread path has been poorly fi nished.
3 Bobbin fails to move smoothly.
4 Bobbin case opening lever provides too
5 Bobbin thread tension is too low.
6 Bobbin has been wound too tightly.
Causes
point or bobbin case resting groove
on the throat plate has sharp edges or
burrs.
excessive clearance at the bobbin case.
point of hook.
or the stroke of the spring is too small.
is excessively advanced or retarded.
is excessively advanced or retarded.
end of the needle eyelet and the blade
point of hook is not correct.
tension spring of the bobbin case.
much clearance at the bobbin.
™ Remove the sharp edges or burrs on the
blade point of hook using a fi ne emery paper.
Buff up the bobbin case resting groove on
the throat plate.
™ Decrease the needle thread tension.
™ Decrease the clearance provided between
the bobbin case opening lever and the bob-
bin. Refer to "21. ADJUSTING THE BOBBIN
CASE OPENING LEVER."
™ Refer to "18. NEEDLE-TO-HOOK RELA-
TION."
™ Apply oil to the surface of the lace of the
hook. (See "6. LUBRICATION.")
™ Increase the needle thread tension.
™ Decrease the tension of the spring and in-
crease the stroke of the spring.
™ Refer to "18. NEEDLE-TO-HOOK RELA-
TION."
™ Refer to "18. NEEDLE-TO-HOOK RELA-
TION."
™ Tighten the presser spring regulator.
™ Refer to "18. NEEDLE-TO-HOOK RELA-
TION."
™ Refer to "19. ADJUSTING THE HOOK
NEEDLE GUARD."
™ Replace the needle with one which is thicker
than the current needle by one count.
™ Thread the bobbin case correctly.
™ Remove rough parts with a fi ne emery paper
or buff it up.
™ Replace the bobbin or hook with a new one.
™ Refer to "21. ADJUSTING THE BOBBIN
CASE OPENING LEVER."
™ Increase the bobbin thread tension.
™ Decrease the tension applied to the bobbin
winder.
– 39 –
Corrective measures