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Trouble Cause Corrective measures Page
5. Stitch skipping often
occurs.
The motions of the needle
and shuttle are not properly
synchronized.
The clearance between the
needle and shuttle is too
large.
The needle is bent.
The driver excessively
bends the needle.
Correct the positions of the needle and
shuttle.
Correct the positions of the needle and
shuttle.
Replace the bent needle.
Correctly position the driver.
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6. The needle thread
comes out on the
wrong side of the ma-
terial.
The needle thread tension
is not high enough.
The tension release mech-
anism fails to work properly.
The needle thread after
thread trimming is too long.
Number of stitches is too
few.
When sewing length is
short (End of needle thread
protrudes on the wrong side
of sewing product.)
Number of stitches is too
few.
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 ten-
sion controller No. 1.
Turn OFF the thread clamp.
Turn OFF the thread clamp.
Use the lower plate, the hole of which
is larger than the presser.
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7. Threads break at time
of thread trimming.
The moving knife has been
improperly position.
Correct the position of the moving
knife.
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8. The thread clamp is
entangled with needle
thread.
The needle thread at the
sewing start is too long.
Tighten thread tension controller No. 1
and make the length of needle thread
33 to 36 mm.
9. Uneven length of the
needle thread
The tension of thread take-
up spring is too low.
Increase the tension of the thread
take-up spring.
10.
The length of needle
thread does not become
short.
The tension of thread ten-
sion controller No. 1 is too
low.
The tension of thread take-
up spring is too high.
The tension of thread take-
up spring is too low and
motion is unstable.
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.
11.
The knotting section of
bobbin thread at 2nd
stitch at the sewing
start appears on the
right side.
Idling of bobbin is large.
The bobbin thread tension
is too low.
The needle thread tension
at 1st stitch is too high.
Adjust the position of the moving
knife.
Increase the bobbin thread tension.
Decrease the needle thread tension
at 1st stitch.
Turn OFF the thread clamp.
Trouble Cause Corrective measures Page
1. The needle thread
slips off at the start of
bar-tacking.
Stitches are slipped at the
start.
The needle thread remain-
ing on the needle after
thread trimming is too short.
The bobbin thread is too
short.
Needle thread tension at
1st stitch is too high.
Thread clamp is unstable
(material is apt to be ex-
panded, thread is hard to
slide, thread is thick, etc.).
Pitch at 1st stitch is too
small.
Adjust the clearance between the nee-
dle and the shuttle to 0.05 to 0.1 mm.
Set soft-start sewing at the start of
bartacking.
Correct the thread tension release tim-
ing of the thread tension controller No. 2.
Increase the tension of the thread
take-up spring, or decrease the ten-
sion of the thread tension controller
No. 1.
Decrease the tension of the bobbin
thread.
Increase the clearance between the
needle hole guide and the counter
knife.
Decrease the tension at 1st stitch.
Decrease the number of rotation at
1st stitch at the sewing start. (Extent
of 600 to 1,000 sti/min)
Increase the number of stitches of
thread clamp to 3 to 4 stitches.
Make the pitch at 1st stitch longer.
Decrease the needle thread tension
at 1st stitch.
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2. Thread often breaks or
synthetic fiber thread
splits nely.
The shuttle or the driver
has scratches.
The needle hole guide has
scratches.
The needle strikes the work
clamp foot.
Fibrous dust is in the
groove of the shuttle race.
The needle thread tension
is too high.
The tension of the thread
take-up spring is too high.
The synthetic fiber thread
melts due to heat generat-
ed on the needle.
Take it out and remove the scratches
using a ne whetstone or buff.
Buff or replace it.
Correct the position of the work clamp
foot.
Take out the shuttle and remove the
brous dust from the shuttle race.
Reduce the needle thread tension.
Reduce the tension.
Use silicone oil.
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3. The needle often
breaks.
The needle is bent.
The needle hits the work
clamp foot.
The needle is too thin for
the material.
The driver excessively
bends the needle.
Needle thread is stepped
on by the work clamp foot
at the start of sewing.
(Needle bend)
Replace the bent needle.
Correct the position of the work clamp
foot.
Replace it with a thicker needle ac-
cording to the material.
Correctly position the needle and the
shuttle.
Widen the distance between the nee-
dle and the wiper. (23 to 25 mm)
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4. Threads are not
trimmed.
(Bobbin thread only)
The counter knife is dull.
The difference in level
between the needle hole
guide and the counter knife
is not enough.
The moving knife has been
improperly positioned.
The last stitch is skipped.
Bobbin thread tension is
too low.
Replace the counter knife.
Increase the bend of the counter knife.
Correct the position of the moving
knife.
Correct the timing between the needle
and the shuttle.
In crease the bobbin thread tension.
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