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32. TROUBLES IN SEWING AND CORRECTIVE MEASURES
Troubles Causes Corrective measures
1. Thread breakage
1
Thread quality is poor.
™
Use another thread of better quality.
2
Thread is too thick for the needle.
™
Change such thread or needle.
3
Thread breakage due to the heated
needle.
™
This occurs on synthetic fi ber thread.
Apply silicon oil lubricant (refer to “11. HOW
TO INSTALL THE SILICON OIL LUBRI-
CATING UNIT”) or reduce the sewing speed.
4
Thread tension is too high.
™
Lessen the thread tension.
Refer to “9. THREAD TENSION”.
5
The thread path of needle, looper,
throat plate, needle guard, looper guide
and all other thread paths are bruised.
™
Make them smooth by means of oilstone or
buffi ng.
6
Excessive thread is remained and
hooked again.
™
Activate the thread take-up tension lever.
Refer to “24. POSITION OF THE THREAD
TAKE-UP LEVER”.
2. Skip-stitch
1
Two consecutive
Stitches are skipped on the needle
thread.
(This trouble is caused when the looper
failed to hook the needle thread.)
™
Verify the looper motion.
Refer to “19. NEEDLE-TO-LOOPER RELA-
TION”.
™
Verify the clearance between the looper and
the needle.
Refer to “19. NEEDLE-TO-LOOPER RELA-
TION”.
™
Check the timing of the looper and the needle.
Refer to “19. NEEDLE-TO-LOOPER RELA-
TION”.
™
Try to increase the tension of the thread take-
up lever depending upon the type of thread.
Refer to “24. POSITION OF THE THREAD
TAKE-UP LEVER”.
™
Verify the needle is attached correctly.
Refer to “6. ATTACHING THE NEEDLE”.
™
Check the position and the timing of the needle
guard.
Refer to “22. MATCHING THE MOTION OF
THE NEEDLE GUARDS WITH THE LOOP
GUIDE”.
™
Verify the thread is correctly passed through.
Refer to “7. THREADING THE MACHINE
HEAD” and “8. THREADING THE LOOP-
ERS”.
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