JUKI MH-481 Manuel D'utilisation page 37

Troubles
2 An independent seam is skipped on the
looper thread.
This trouble is caused when the needle
failed ·to come down through a trian-
gular loop formed by the looper thread.
3 Seam is skipped on the needle thread
due to insuffi cient interlooping.
This trouble is caused when the needle
thread is inclined extremely to the left.
If it is caused in the use of a chemical
fi ber thread.
If it is caused in the use of a synthetic
fi ber thread.
3. Inadequate tight- 1 Needle thread tension is too low.
ness of stitches
2 Looper thread tension is too high.
3 Looper thread take-up does not supply
a suffi cient length of thread.
4 Thread is too thick for the needle size.
Causes
Needle
Looper
Needle
Looper
– 28 –
Corrective measures
™ Verify the looper motion.
Verify the clearance between the looper and
the needle.
Refer to "19. NEEDLE-TO-LOOPER RELA-
TION".
™ Check the timing of the looper thread take-up.
Refer to "23. POSITIONING THE LOOPER
THREAD TAKE-UP".
™ Adjust the position of the thread spreader
hook.
Refer to "21. THREAD SPREADER".
™ Increase the looper thread tension slightly.
Refer to "9. THREAD TENSION".
™ Verify the thread is correctly passed through.
Refer to "7. THREADING THE MACHINE
HEAD" and "8. THREADING THE LOOP-
ERS".
™ Verify the looper motion.
Verify the clearance between the looper and
the needle.
Refer to "19. NEEDLE-TO-LOOPER RELA-
TION".
™ Reduce the sewing speed.
™ Apply silicon oil lubricant.
Refer to "11. HOW TO INSTALL THE SILI-
CON OIL LUBRICATING UNIT".
™ Use a needle for chemical fi ber threads.
™ Make the scooping amount of looper greater.
Refer to "19. NEEDLE-TO-LOOPER RELA-
TION".
™ Reduce the sewing speed.
™ Apply silicon oil lubricant.
Refer to "11. HOW TO INSTALL THE SILI-
CON OIL LUBRICATING UNIT".
™ Tighten the needle thread tension nut.
Refer to "9. THREAD TENSION".
™ Loosen the looper thread tension nut.
Refer to "9. THREAD TENSION".
™ Change the threading order in the looper thread
guide.
Refer to "23. POSITIONING THE LOOPER
THREAD TAKE-UP".
™ Try to use a different needle.
Refer to "6. ATTACHING THE NEEDLE".