32. Troubles In Sewing And Corrective Measures - JUKI MH-481 Serie Manual De Instrucciones

32. TROUBLES IN SEWING AND CORRECTIVE MEASURES

Troubles
1. Thread breakage 1 Thread quality is poor.
2 Thread is too thick for the needle.
3 Thread breakage due to the heated
needle.
4 Thread tension is too high.
5 The thread path of needle, looper,
throat plate, needle guard, looper guide
and all other thread paths are bruised.
6 Excessive thread is remained and
hooked again.
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.)
Causes
– 46 –
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. HOW
TO INSTALL THE SILICON OIL LUBRI-
CATING UNIT") or reduce the sewing speed.
™ Lessen the thread tension.
Refer to "9. THREAD TENSION".
™ Make them smooth by means of oilstone or
buffi ng.
™ Activate the thread take-up tension lever.
Refer to "24. POSITION OF THE THREAD
TAKE-UP LEVER".
™ 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".