JUKI LU-2860V-7, Instruction Manual

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11. TROUBLES IN SEWING AND CORRECTIVE MEASURES
Troubles Causes Corrective measures
1. 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
"8-4. Adjusting the bobbin case
opening lever" p.109 .
○ Refer to "8-1. Needle-to-hook relation"
p.107 .
○ Adjust the amount of oil in the hook properly.
Refer to "2-19. Lubrication" p.23 .
○ Increase the needle thread tension.
○
Decrease the tension of the spring and
increase the stroke of the spring.
○ Refer to "8-1. Needle-to-hook relation"
p.107 .
2. Stitch skipping
(Two or three stitches
skip at the beginning
of sewing.)
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.
⑥ The bobbin thread clamp pressure is low.
○ Refer to "8-1. Needle-to-hook relation"
p.107 .
○ Increase the presser foot pressure.
○
Refer to "8-1. Needle-to-hook relation"
p.107 .
○ Refer to "8-3. Adjusting the hook needle
guard" p.109 .
○ Replace the needle with one which is thicker
than the current needle by one count.
○ Increase the bobbin thread clamp pressure.
Refer to "8-5. Adjusting the position of
counter knife, knife pressure and clamp
pressure" p.110
.
3. Loose stitches
(Revere feed
stitching)
①
Bobbin thread does not pass through the
tension spring of the inner hook.
② The hook, feed dog and/or the thread
path in thread guide, etc. have worn out
or have flaws.
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.
⑦ The needle thread tension is low while
carrying out the reverse feed stitching.
⑧ The needle does not match the needle
hole in feed dog.
○
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 "8-4. Adjusting the bobbin case
opening lever" p.109 .
○
Increase the bobbin thread tension.
○ Decrease the tension applied to the bobbin
winder.
○ Advance the feed (horizontal feed) timing.
(Refer to the Engineer's Manual for the
adjustment procedure.)
○ Change the feed dog with an appropriate one.
(Refer to the Parts List.)