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Trouble
5. Stitch skipping often
occurs.
6. The needle thread
comes out on the
wrong side of the mate-
rial.
7. Threads break at time
of thread trimming.
8. Uneven length of the
needle thread
9. The length of needle
thread does not become
short.
10. The knotting section of
bobbin thread at 2nd
stitch at the sewing
start appears on the
right side.
Cause
① The motions of the needle
and shuttle are not properly
synchronized.
② The clearance between the
needle and shuttle is too
large.
③ The needle is bent.
④ The driver excessively
bends the needle.
① The needle thread tension
is not high enough.
② The tension release mecha-
nism fails to work properly.
③ The needle thread after
thread trimming is too long.
④ Number of stitches is too
few.
⑤ When sewing length is
short (End of needle thread
protrudes on the wrong side
of sewing product.)
① The moving knife has been
improperly position.
① The tension of thread take-
up spring is too low.
① The tension of thread ten-
sion controller No. 1 is too
low.
② The tension of thread take-
up spring is too high.
③ The tension of thread take-
up spring is too low and
motion is unstable.
① Idling of bobbin is large.
② The bobbin thread tension
is too low.
－
Corrective measures
◦ Correct the positions of the needle and
shuttle.
◦ Correct the positions of the needle and
shuttle.
◦ Replace the bent needle.
◦ Correctly position the driver.
◦ Increase the needle thread tension.
◦ Check whether or not the tension disc
No. 2 is released during bar-tracking.
◦ Increase the tension of the thread
tension controller No. 1.
◦ Use the lower plate, the hole of which
is larger than the presser.
◦ Change of the sewing pattern.
◦ Correct the position of the moving
knife.
◦ Increase the tension of the thread
take-up spring.
◦ Increase the tension of thread tension
controller No. 1.
◦ Decrease the tension of thread take-
up spring.
◦ Increase the tension of thread take-
up spring and lengthen the stroke as
well.
◦ Adjust the position of the moving
knife.
◦ Increase the bobbin thread tension.
－
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