23. Troubles In Sewing And Corrective Measures - JUKI LU-1508N Manuel D'utilisation

23. TROUBLES IN SEWING AND CORRECTIVE MEASURES

Troubles
1. Thread breakage
(Thread frays or is worn
out.)
(Needle thread trails 2
to 3 cm from the wrong
side of the fabric.)
2. Stitch skipping
3. Loose stitches
Causes
1 Thread path, needle point, hook blade
point or bobbin case resting groove on
the throat plate has sharp edges or burrs.
2 Needle thread tension is too high.
3 Bobbin case opening lever provides an
excessive clearance at the bobbin case.
4 Needle comes in contact with the blade
point of hook.
5 Amount of oil in the hook is too small.
6 Needle thread tension is too low.
7 Thread take-up spring works excessively
or the stroke of the spring is too small.
8 Timing between the needle and the hook
is excessively advanced or retarded.
1 Timing between the needle and the hook
is excessively advanced or retarded.
2 Pressure of the presser foot is too low.
3 The clearance provided between the top
end of the needle eyelet and the blade
point of hook is not correct.
4 Hook needle guard is not functional.
5 Improper type of needle is used.
1 Bobbin thread does not pass through the
tension spring of the inner hook.
2 Thread path has been poorly fi nished.
3 Bobbin fails to move smoothly.
4 Bobbin case opening lever provides too
much clearance at the bobbin.
5 Bobbin thread tension is too low.
6 Bobbin has been wound too tightly.
™ 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 bobbin.
Refer to "18. ADJUSTING THE BOBBIN
CASE OPENING LEVER".
™ Refer to "16. NEEDLE-TO-HOOK
RELATION".
™ Adjust the amount of oil in the hook
properly.
Refer to "4. LUBRICATION".
™ Increase the needle thread tension.
™ Decrease the tension of the spring and
increase the stroke of the spring.
™ Refer to "16. NEEDLE-TO-HOOK
RELATION".
™ Refer to "16. NEEDLE-TO-HOOK
RELATION".
™ Tighten the presser spring regulator.
™ Refer to "16. NEEDLE-TO-HOOK
RELATION".
™ Refer to "17. ADJUSTING THE HOOK
NEEDLE GUARD".
™ Replace the needle with one which is
thicker than the current needle by one
count.
™ Thread the bobbin thread 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 "18. ADJUSTING THE BOBBIN
CASE OPENING LEVER".
™ Increase the bobbin thread tension.
™ Decrease the tension applied to the
bobbin winder.
– 51 –
Corrective measures