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Trouble
① The tension of thread take-up
8. Uneven length of
the needle thread
② The thread trimmer fails to trim
③ Loop spreading fault of the
① Idling of bobbin is large.
9. The knotting
section of bobbin
② The bobbin thread tension is too
thread at 2nd
stitch at the
③ The needle thread tension at 1st
sewing start
appears on the
right side.
① Needle entry of the last needle
10. Wiper fails to
work. (Return is
defective.)
① Thread waste accumulates near
11. Thread trimmed
at the beginning
of sewing is not
collected.
② Trimmed thread is caught
③ Length of needle thread remaining
① The thread is not trimmed
12. Thread trimmed
at the beginning
of sewing is
entangled.
Cause
spring is too low.
the thread at the correct timing.
moving knife (Needle thread chip
remains near the hook)
low.
stitch is too high.
is the same as that of the sewing
start, and the resistance of thread
and cloth is large.
the thread trimmer connecting
bar.
between the shuttle race and the
counter knife.
at the needle is too short. The
thread untwists and separates
into single yarns.
completely to leave a single yarn.
The remaining single yarn is
entangled.
Corrective measures
○ Increase the tension of the thread take-
up spring.
○ Adjust the position of the moving knife
and counter knife correctly.
○ Adjust the initial position of the moving
knife correctly.
○ A just the position of the moving knife.
○ Increase the bobbin thread tension.
○ Decrease the needle thread tension at
1st stitch.
○ Shift the needle entry point of the last
needle.
○ Defective air pressure setting may be the
cause of trouble. Set the air pressure to
the optimum value (0.2 - 0.3 MPa).
○ Adjust the position of shuttle race.
○ Adjust the length of needle thread
remaining at the needle to the optimum
value (40 mm to 50 mm)
○ Change the knife or the throat plate asm.
with an appropriate one.
○ Faulty thread trimming may be the
cause. (Refer to
trimmed.".)
– 154 –
"4. Threads are not
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