JUKI LH-3500A series Instruction Manual page 56

TROUBLES
3. Loose sttch
4. Thread trmmng
falure
5. Amount of dlng s
excessvely large.
6�. Clamp falure
CAUSES
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.
7 The presser foot does not securely
press the mult-layered secton of
the materal.
8 Needle eyelet s too small for
thckness of thread, preventng
smooth take-up moton of the
thread take-up lever.
9 Wth respect to tensng of thck
thread, nether needle thread
tenson nor bobbn thread tenson
can be ncreased, resultng n
producton of solated dlng loops.
!0 Isolated dlng loops are produced
durng the reverse feed sttchng.
1 The poston of the movng knfe s
not correct.
2 Bobbn thread cannot be trmmed
by droppng the thread trmmer.
1 The counter knfe pressure s
nadequate.
2 Backlash between the bobbn and
the bobbn case s excessvely
large.
3 The dlng preventon sprng does
not work adequately.
4 The dlng preventon sheet s not
placed.
5 Thread trmmng speed s too hgh.
1 The clamp pressure has adjusted
to an excessvely hgh or low
value.
2 The clamp pressure works
excessvely, resultng permanent
set n fatgue of the clamp plate
clamp sprng.
3 The bobbn thread slps off due to
the bobbn thread slack preventon
sprng of the cap hook.
4 �ue to dfference n thread count
number between the needle
thread and bobbn thread, they
excessvely tangle wth each other
at the tme of thread trmmng.
5 The feed dog heght s too low.
CORRECTIVE MEASURES
™ 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.
™ Change presser foot wth the hngng
presser (B52452FBE).
(The presser foot wth large front and rear
elevaton angles s preferable.)
™ Retard the hook tmng by 2 to 3 degrees.
™ Use the needle thread take-up eyelet.
™ Use the needle thread presser.
™ Use the bobbn thread tenson sprng t0.3
(226�2808).
™ Retard the hook tmng.
™ Refer to
the moving knife" p.
™ Use the feed dog wth thcker teeth (2 mm).
™ Retard the thread trmmng cam tmng by 5°.
™ Increase the knfe pressure.
Refer to
presser spring" p.
™ Re-select the bobbn and the bobbn case.
™ Increase the sprng pressure.
™ Place the sheet n poston.
™ �ecrease the thread trmmng speed.
™ Increase or decrease the clamp pressure.
Refer to
presser spring" p.
™ Change the clamp plate clamp sprng wth a
new one.
™ Remove the bobbn thread slack preventon
sprng.
™ Use the optonal clamp style cap hook.
™ Increase the tenson appled by the tenson
controller No. .
™ Retard the tmng of the thread trmmng
cam.
™ Increase the feed dog heght.
– 54 –
"6-5. Adjusting the inner hook
37.
"6-9. Adjusting the position of
40.
"6-8. Adjusting the thread
39.
"6-8. Adjusting the thread
39.