24. Troubles In Sewing And Corrective Measures - JUKI MH-380 Instruction Manual

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24. TROUBLES IN SEWING AND CORRECTIVE MEASURES

Troubles
1. Thread breakage 1 Thread quality is poor.
2. Skip-stitch
Causes
2 Thread is too thick for the needle.
3 Thread breakage due to the heated
needle.
4 Thread tension is too high.
5 Thread path of needle, looper, throat
plate or needle guard is bruised.
6 Excessive thread is remained and
hooked again.
1 Two consecutive
Stitches are skipped on the needle
thread.
(This trouble is caused when the looper
failed to hook the needle thread.)
Corrective measures
™ Use another thread of better quality.
™ Change such thread or needle.
™ This occurs on synthetic fi ber thread.
Apply silicon oil lubricant (refer to "11. AT-
TACHING THE NEEDLE") or reduce the
sewing speed.
™ Lessen the thread tension.
Refer to "8. THREAD TENSION".
™ Make them smooth by means of oilstone or
buffi ng.
™ Activate the thread take-up tension lever.
Refer to "20. POSITION OF THE THREAD
TAKE-UP LEVER".
™ Verify the looper motion.
Refer to "17. NEEDLE-TO-LOOPER RELA-
TION".
™ Verify the clearance between the looper and
the needle.
Refer to "17. NEEDLE-TO-LOOPER RELA-
TION".
™ Check the timing of the looper and the needle.
Refer to "17. NEEDLE-TO-LOOPER RELA-
TION".
™ Re-adjust the frame thread eyelet.
Refer to "21. POSITION OF THE FRAME
THREAD EYELET".
™ Try to increase the tension of the thread take-
up lever depending upon the type of thread.
Refer to "20. POSITION OF THE THREAD
TAKE-UP LEVER".
™ Verify the needle is attached correctly.
Refer to "11. ATTACHING THE NEEDLE".
™ Check the position and the timing of the needle
guard.
Refer to "18. MATCHING THE MOTION OF
THE NEEDLE GUARDS WITH THE LOOP
GUIDE".
™ Verify the thread is correctly passed through.
Refer to "6. THREADING THE MACHINE
HEAD" and "7. THREADING THE LOOP-
ERS".
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