– 72 –
IX. TROUBLES AND CORRECTIVE MEASURES
Troubles
Causes
Corrective measures
Page
1. Needle thread break-
age
1. Thread tension at parallel section is too high.
2. Pressure or stroke of thread take-up spring is
too large.
3. There is a burr or scratch on the blade point
of hook.
4. Hook timing is not proper.
5. There is a scratch on the thread path.
6. Attaching needle is wrong.
7. Needle is too thin.
8. Needle tip is damaged.
9. Thread breaks when it is bent.
○ Decrease the thread tension at parallel
section.
○ Decrease the tension of thread take-up
spring or decrease its stroke.
○ Buff the blade point of hook. Or, replace
the hook.
○ Adjust again the hook timing with timing
gauge.
○ Polish the thread path with sand paper
and buff it.
○ Adjust again the direction, height, etc.
○ Replace the needle with a thicker one.
○ Replace the needle.
○ Do not pass the thread through the thread
guide pin.
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2. Needle thread slips off.
1. Needle thread trimmer opens too early.
2. Whip stitching is not formed at the start of
sewing.(Tension at the start of sewing is too
high.)
3. Threading needle thread is wrong.
4. Speed at the start of sewing is too fast.
○ Delay the opening timing of the needle
thread trimmer.
○ Decrease tension at the start of sewing.
○ Thread properly again.
○ Set the soft-start function.
3. Wobbling at parallel
section
1. Thread tension at parallel section is too low.
2. Bobbin thread tension is too high.
3. Pre-tension is too low.
○ Increase the thread tension at parallel sec
-
tion.
○ Decresase bobbin thread tension.
(Purl stitching : 0.05 to 0.1N )
○ Increase pre-tension.
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4. Wobbling at the start
of sewing
1. Thread tension at parallel section is too low.
2. Position of needle thread trimmer is too high.
3. Stroke of thread take-up spring is too large.
○ Increase the thread tension at parallel sec
-
tion.
○ Lower the needle thread trimmer to such
an extent that it does not come in contact
with the presser.
○ Decrease the stroke of thread take-up
spring.
5. Needle thread appears
on the wrong side of
material at bar-tacking
section in dumpling
condition.
1. Bar-tacking thread tension is too low.
2. Bobbin thread tension is too high.
3. Number of stitches of radial shape is too
many.
4. Tension at the end of sewing is too low.
○ Increase the bar-tacking thread tension.
○ Decresase the bobbin thread tension.
(0.05 to 0.1N )
○ Decrease the number of stitches.
○ Increase tension at the end of sewing.
6. Stitches float.
1. Bobbin thread tension is too low.
2. Bobbin thread comes off bobbin case.
○ Increase the bobbin thread tension.
○ Perform proper threading the bobbin case.
○ Take care that the winding amount of bob
-
bin thread is not excessive.
7. Stitch skipping
1. Button hole is small in terms of the size of
presser.
2. Material flops because of light-weight.
3. Attaching needle is wrong.
4. Needle is bent.
5. There is a burr or scratch on the blade point
of hook.
○ Replace the presser with a smaller one.
○ Delay the hook-to-needle timing.
(Lower the needle bar by 0.5 mm.)
○ Adjust again the direction, height, etc.
○ Replace the needle.
○ Buff the blade top of hook. Or, replace the
hook.
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8. Thread frays.
1. Number of stitches of tie stitching is too small.
2. Width of tie stitching is too wide.
○ Increase the number of stitches of tie
stitching at the end of sewing.
○ Narrow the width of tie stitching at the end
of sewing.
9. Length of needle
thread remaining at
the end of sewing is
too long.
1. Width of tie stitching is too narrow.
2. Tension of tie stitching is too low.
○ Widen the width of tie stitching at the end
of sewing.
○ Increase tension at the end of sewing.
