Troubles In Sewing And Corrective Measures - JUKI PLC-2700 Series Instruction Manual

8. TROUBLES IN SEWING AND CORRECTIVE MEASURES

Troubles
① Thread path, needle point, hook blade point
1. Thread breakage
(Thread frays or is
worn out.)
② Needle thread tension is too high.
③ Bobbin case opening lever provides an
④ Needle comes in contact with the blade point
⑤ Amount of oil in the hook is too small.
⑥ Needle thread tension is too low.
(Needle thread trails
⑦ Thread take-up spring works excessively or
2 to 3 cm from the
wrong side of the
⑧ Timing between the needle and the hook is
fabric.)
① Timing between the needle and the hook is
2. Stitch skipping
② Pressure of the presser foot is too low.
③ The clearance provided between the top end
④ Hook needle guard is not functional.
⑤ Improper type of needle is used.
① Bobbin thread does not pass through the
3. Loose stitches
② Thread path has been poorly finished.
③ Bobbin fails to move smoothly.
④ Bobbin case opening lever provides too
⑤ Bobbin thread tension is too low.
⑥ Bobbin has been wound too tightly.
① Thread tension given by the tension
4. Thread slips off
the needle eyelet
simultaneously with
thread trimming.
① Thread tension given by the tension
5. Thread slips off the
needle eyelet at the
② Clamp spring has improper shape.
start of sewing.
③ Bobbin thread tension is too low.
① The blades of moving knife and counter knife
6. Thread is not cut
sharply.
② The knives have blunt blades.
③ Bobbin thread tension is too low.
① Initial position of the moving knife has been
7. Thread remains uncut
after thread trimming.
② Bobbin thread tension is too low.
(Bobbin thread
trimming failure
when stitch length is
comparatively short.)
① The needle thread is caught in the hook.
8. Thread breaks at the
start of sewing after
thread trimming.
① The feed amount of the top feed is
9. When a heave-weight
material is sewn, the
material warps.
Causes
or bobbin case resting groove on the throat
plate has sharp edges or burrs.
excessive clearance at the bobbin case.
of hook.
the stroke of the spring is too small.
excessively advanced or retarded.
excessively advanced or retarded.
of the needle eyelet and the blade point of
hook is not correct.
tension spring of the inner hook.
much clearance at the bobbin.
controller No. 1 is too high.
controller No. 1 is too high.
have been improperly adjusted.
improperly adjusted.
inadequate.
○ 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
"4-6. Adjusting the bobbin case opening
to
lever" p.31
○ Refer to
"4-4. Needle-to-hook relation" p.30
○ Adjust the amount of oil in the hook properly. Refer
to "3-5. Lubrication"
○ Increase the needle thread tension.
○ Decrease the tension of the spring and increase
the stroke of the spring.
○ Refer to
"4-4. Needle-to-hook relation" p.30
○ Refer to
"4-4. Needle-to-hook relation" p.30
○ Tighten the presser spring regulator.
○ Refer to
"4-4. Needle-to-hook relation" p.30
○ Refer to
"4-5. Adjusting the hook needle guard"
p.31 .
○ Replace the needle with one which is thicker than
the current needle by one count.
○ 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
"4-6. Adjusting the bobbin case
opening lever" p.31
○ Increase the bobbin thread tension.
○ Decrease the tension applied to the bobbin winder.
○ Decrease the thread tension given by the tension
controller No. 1.
○ Decrease the thread tension given by the tension
controller No. 1.
○ Replace the clamp spring with a new one or
correct the current one.
○ Increase the bobbin thread tension.
○ Refer to
"4-7. Position of the counter knife and
adjustment of the knife pressure" p.32
○ Replace the moving knife and counter knife with
new ones, or correct the current ones.
○ Increase the bobbin thread tension.
○ Refer to the Engineer's Manual.
○ Increase the bobbin thread tension.
○ Shorten the length of thread remaining on the
needle after thread trimming.
Refer to "4-2. Thread tension" p.28
○ Decrease the feed dog height and reduce the
feed amount of the bottom feed. (Refer to the
Engineer's Manual for the adjustment procedure.)
– 44 –
Corrective measures
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p.17.
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