JUKI LU-2220N-7, Instruction Manual

Page: 35 / 36

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32. TROUBLES IN SEWING AND CORRECTIVE MEASURES
Troubles Causes Corrective measures
. Thread
breakage
(Thread frays
or is worn out.)
(Needle thread
trails 2 to 3
cm from the
wrong side of
the fabric.)
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.
™
Remove the sharp edges or burrs on the
blade point of hook using a fine 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 “24. ADJUSTING THE
BOBBIN CASE OPENING LEVER.”
™
Refer to “22. NEEDLE-TO-HOOK
RELATION.”
™
Adjust the amount of oil in the hook
properly. See “15. ADJUSTING THE
AMOUNT OF OIL IN THE HOOK.”
™
Increase the needle thread tension.
™
Decrease the tension of the spring and
increase the stroke of the spring.
™
Refer to “22. NEEDLE-TO-HOOK
RELATION.”
2. Stitch skipping
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.
™
Refer to “22. NEEDLE-TO-HOOK
RELATION.”
™
Tighten the presser spring regulator.
™
Refer to “22. NEEDLE-TO-HOOK
RELATION.”
™
Refer to “23. ADJUSTING THE HOOK
NEEDLE GUARD.”
™
Replace the needle with one which is thicker
than the current needle by one count.
3. Loose stitches
1
Bobbin thread does not pass through
the tension spring of the inner hook.
2
Thread path has been poorly finished.
3
Bobbin fails to move smoothly.
4
Bobbin case opening lever provides
too much clearance at the bobbin.
5
Needle thread tension is too low.
6
Bobbin thread tension is too low.
7
Bobbin has been wound too tightly.
8
Thread is thick.
9
Thread supplying amount of thread
take-up lever is excessively large.
™
Thread the bobbin thread correctly.
™
Remove rough parts with a fine emery
paper or buff it up.
™
Replace the bobbin or hook with a new
one.
™
Refer to “24. ADJUSTING THE BOBBIN
CASE OPENING LEVER.”
™
Increase the needle thread tension.
™
Increase the bobbin thread tension.
™
Decrease the tension applied to the
bobbin winder.
™
Replace the feed dog with one for thick
thread.
™
Remove the pre-tension of needle thread
clamp device.
™
Increase the needle count.
™
Move the thread take-up thread guide to
the right side to decrease the supplying
amount by the thread take-up lever.