Troubles And Corrective Measures - JUKI LH-3500 Series Instruction Manual

9. TROUBLES AND CORRECTIVE MEASURES

TROUBLES
. Thread breakage
(Thread s
untwsted or
scraped.)
(Needle thread 2 to
3 cm s left on the
wrong sde of the
fabrc.)
2. Sttch skppng
3. Loose sttch
CAUSES
1 There s a sharp edge or burr on
the thread path, needle pont,
hook blade pont or bobbn case
restng groove on the throat plate.
2 Needle thread tenson s too hgh.
3 Bobbn case openng lever
provdes an excessve clearance
at the bobbn case.
4 Hook blade pont hts the needle.
5 Hook s not lubrcated properly.
6 Needle thread tenson s too low.
7 Thread take-up sprng s too tght
and ts stroke s too small.
8 Needle-to-hook tmng s wrong.
9 Thread untwsts.
!0 Unform thread loops cannot be
formed when makng chan-off
thread.
1 Clearance between the needle
and the hook blade pont s too
great.
2 Needle-to-hook relaton s wrong.
3 Pressng force of the presser foot
s not enough.
4 Needle bar heght s wrong.
5 Needles are a lttle too thn.
6 Synthetc thread or thn thread s
used.
1 Bobbn thread does not pass
through the forked end of the
tenson sprng on the bobbn case.
2 Thread path has rough surface.
3 Bobbn does not spn smoothly.
4 Bobbn case openng lever
provdes too much clearance at
the bobbn.
5 Bobbn thread tenson s too low.
6 Bobbn s wound too tghtly.
CORRECTIVE MEASURES
™ Remove sharp edge or burr using a fine
sandpaper. Polsh the surface of the
bobbn case restng groove on the throat
plate using a buffing wheel.
™ Adjust the needle thread tenson.
™ Reduce the clearance.
(Refer to
guide", P.
™ Refer to
relation", P.
™ Increase the amount of ol suppled to the
hook accordng to
amount of oil in the hook", P.
™ Adjust the needle thread tenson.
™ Reduce the tenson of the sprng and
ncrease the stroke.
™ Refer to
relation", P.
™ Wnd the thread on the needle.
™ Use the thread gude equpped wth felt
pad.
™ Refer to
relation", P.
™ Refer to
relation", P.
™ Tghten the presser sprng regulator.
™ Refer to
relation", P.
™ Replace the needle by thcker ones.
™ Wnd the thread on the needle.
™ Thread the bobbn case correctly.
™ Remove rough surface using a fine
sandpaper or polsh the surface usng a
buffing wheel.
™ Replace the bobbn or the hook.
™ Refer to
guide", P.
™ Adjust the bobbn thread tenson.
™ Adjust the tenson components on the
bobbn wnder.
– 47 –
"6-4. Adjusting the inner hook
30.)
"4-15. Needle-to-hook
21.
"4-4. Adjusting the
10.
"4-15. Needle-to-hook
21.
"4-15. Needle-to-hook
21.
"4-15. Needle-to-hook
21.
"4-15. Needle-to-hook
21.
"6-4. Adjusting the inner hook
30.