Troubles And Corrective Measures - JUKI LH-3528 Instruction Manual

9. TROUBLES AND CORRECTIVE MEASURES

TROUBLES
. Thread 1 There is a sharp edge or burr on the
breakage
(Thread is
untwisted or
scraped.) 2 Needle thread tension is too high.
3 Bobbin case opening lever provides an
4 Hook blade point hits the needle.
5 Hook is not lubricated properly.
(Needle thread 2 6 Needle thread tension is too low.
to 3 cm is left on 7 Thread take-up spring is too tight and its
the wrong side
of the fabric.) 8 Needle-to-hook timing is wrong.
9 Thread untwists.
!0 Uniform thread loops cannot be formed
2. Stitch skipping 1 Clearance between the needle and the
2 Needle-to-hook relation is wrong.
3 Pressing force of the presser foot is not
4 Needle bar height is wrong.
5 Needles are a little too thin.
6 Synthetic thread or thin thread is used.
3. Loose stitch 1 Bobbin thread does not pass through
2 Thread path has rough surface.
3 Bobbin does not spin smoothly.
4 Bobbin case opening lever provides too
5 Bobbin thread tension is too low.
6 Bobbin is wound too tightly.
CAUSES
thread path, needle point, hook blade
point or bobbin case resting groove on
the throat plate.
excessive clearance at the bobbin case.
stroke is too small.
when making chain-off thread.
hook blade point is too great.
enough.
the forked end of the tension spring on
the bobbin case.
much clearance at the bobbin.
CORRECTIVE MEASURES
™ Remove sharp edge or burr using a fine
sandpaper. Polish the surface of the
bobbin case resting groove on the throat
plate using a buffing wheel.
™ Adjust the needle thread tension.
™ Reduce the clearance. (Refer to "6-4.
Adjusting the inner hook guide".)
™ Refer to "4-4. Needle-to-hook relation".
™ Increase the amount of oil supplied to
the hook according to "4-3. Adjusting the
amount of oil in the hook".
™ Adjust the needle thread tension.
™ Reduce the tension of the spring and
increase the stroke.
™ Refer to "4-4. Needle-to-hook relation".
™ Wind the thread on the needle.
™ Use the thread guide equipped with felt
pad.
™ Refer to "4-4. Needle-to-hook relation".
™ Refer to "4-4. Needle-to-hook relation".
™ Tighten the presser spring regulator.
™ Refer to "4-4. Needle-to-hook relation".
™ Replace the needle by thicker ones.
™ Wind the thread on the needle.
™ Thread the bobbin case correctly.
™ R e m o v e r o u g h s u r f a c e u s i n g a f i n e
sandpaper or polish the surface using a
buffing wheel.
™ Replace the bobbin or the hook.
™ Refer to "6-4. Adjusting the inner hook
guide".
™ Adjust the bobbin thread tension.
™ Adjust the tension components on the
bobbin winder.
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