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