Troubles And Corrective Measures (Sewing Conditions) - JUKI LK-1941 Manuel D'utilisation

5. Troubles and corrective measures (sewing conditions)

Trouble
1. The needle thread
slips off at the start of
bar-tacking.
2. Thread often breaks
o r s y n t h e t i c f i b e r
thread splits finely.
3. The needle often
breaks.
4. Treads are not
trimmed.
5. Stitch skipping often
occurs.
6. The needle thread
comes out on the
wrong side of the
material.
7. When synthetic fiber thread
is used, at the start or end
of sewing, needle thread
rises or remaining of needle
thread is excessive.
58
Cause
1
Stitches are slipped at the start.
2
The needle thread remaining on the needle
after thread trimming is too short.
3
The bobbin thread is too short.
1
The hook or the inner hook stopper has
scratches.
2
The needle hole guide has scratches.
3
Partial catch of thread by hook due to needle
deflection
4
The needle thread tension is too high.
5
The tension of the thread take-up spring is
too high.
6
The synthetic fiber thread melts due to heat
generated on the needle.
7
Thread breakage due to partial catch of
thread by hook when sewing seat belt
8
Needle stitcks in fabric yarn.
1
The needle is bent.
2
The needle is too thin for the material.
3
Feed timming is excessively slow.
1
Position of thread trimming is improper.
2
The moving knife has been improperly
positioned.
3
The last stitch is skipped.
4
Pitch at the last stitch is too small.
(Knife type)
1
The counter knife is dull.
2
The difference in level between the needle
hole guide and the counter knife is not
enough.
(Hot wire type)
1
Temperature setting is too low.
2
The hot wire plate comes in contact with the
needle hole guide.
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.
1
The needle thread tension is not high enough.
2
The needle thread after thread trimming is too long.
1
In case of synthetic fiber thread, the thread is
harder than other threads and penetration
resistance to material is small.
Corrective measures
™
Adjust the clearance between the needle and the
shuttle to 0.05 to 0.1 mm.
™
Set soft-start sewing at the start of bartacking.
™
Change the pitch at the start of sewing. (Increase
or decrease.)
™
Increase the rising amount of the disk of thread
tension controller No. 2.
™
Increase the rising amount of the disk of auxiliary
thread tension.
™
Increase the tension of the thread take-up spring,
or decrease the tension of the thread tension
controller No. 1.
™
Increase the clearance between the needle hole
guide and the counter knife. (Knife type)
™
Lower the counter knife. (Knife type)
™
Adjust the position of the moving knife. (Hot wire
type)
™
Decrease the tension of the bobbin thread.
™
Increase the clearance between the needle hole
guide and the counter knife. (Knife type)
™
Lower the counter knife. (Knife type)
™
Take it out and remove the scratches using a fine
whetstone or buff.
™
Buff or replace it.
™
Use a hook suitable for the needle count number.
™
Reduce the needle thread tension.
™
Reduce the tension.
™
Use silicone oil.
™
Use the needle cooler.
™
Use an oval needle hole guide.
™
Use the ball-point needle.
™
Replace the bent needle.
™
Replace it with a thicker needle according to the
material.
™
Make the feeding timing fast.
™
Enter thread trimming at the proper position.
™
Correct the position of the moving knife.
™
Correct the timing between the needle and the
shuttle.
™
Increase the pitch of the last stitch.
™
Replace the counter knife.
™
Increase the bend of the counter knife.
™
Make the setting high.
™
Adjust the position of the hot wire plate.
™
Correct the positions of the needle and shuttle.
™
Correct the positions of the needle and shuttle.
™
Replace the bent needle.
™
Increase the needle thread tension.
™
Delay the feed timing.
™
Increase the tension of the thread tension
controller No. 1.
™
When making a pattern, set the sewing pitch at
the start and end of sewing to 1 mm or less.
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