– 142 –
1-17. troubles and corrective measures (sewing conditions)
trouble
cause
corrective measures
Page
1. The needle
thread slps
off at the
start of bar-
tackng.
1
Sttches are slpped at the start.
2
The needle thread remanng on the
needle after thread trmmng s too
short.
3
The bobbn thread s too short.
4
Needle thread tenson at 1st sttch s
too hgh.
5
Thread clamp s unstable (materal s
apt to be expanded, thread s hard to
slde, thread s thck, etc.).
6
Thread clamp s unstable (materal s
apt to be expanded, thread s hard to
slde, thread s thck, etc.).
™
Adjust the clearance between the needle
and the shuttle to 0.05 to 0.1 mm.
™
Set the sewng machne so that the sewng
speed s lowered at the begnnng of sewng.
™
Correct the thread tenson release tmng of
the thread tenson controller No. 2.
™
Increase the tenson of the thread take-
up sprng, or decrease the tenson of the
thread tenson controller No. 1.
™
Decrease the tenson of the bobbn thread.
™
Increase the clearance between the needle
hole gude and the counter knfe.
™
Decrease the tenson at 1st sttch.
™
Decrease the number of rotaton at 1st
sttch at the sewng start. (Extent of 600 to
1,000 st/mn)
™
Increase the number of sttches of thread
clamp to 3 to 4 sttches.
™
Make the ptch at 1st sttch longer.
™
Decrease the needle thread tenson at 1st
sttch.
131
95
-
18,19
18
132
95
95
96
-
95
2. Thread
often
breaks or
synthetc
fiber thread
splits finely.
1
The shuttle or the drver has
scratches.
2
The needle hole gude has scratches.
3
The needle strkes the work clamp
foot.
4
Fbrous dust s n the groove of the
shuttle race.
5
The needle thread tenson s too hgh.
6
The tenson of the thread take-up
sprng s too hgh.
7
The synthetic fiber thread melts due to
heat generated on the needle.
™
Take t out and remove the scratches usng
a fine whetstone or buff.
™
Buff or replace t.
™
Correct the poston of the work clamp foot.
™
Take out the shuttle and remove the fibrous
dust from the shuttle race.
™
Reduce the needle thread tenson.
™
Reduce the tenson.
™
Use slcone ol.
-
-
-
131
18
19
17
3. The needle
often
breaks.
1
The needle s bent.
2
The needle hts the work clamp foot.
3
The needle s too thn for the materal.
4
The drver excessvely bends the
needle.
5
Needle thread s stepped on by the
work clamp foot at the start of sewng.
(Needle bend)
™
Replace the bent needle.
™
Correct the poston of the work clamp foot.
™
Replace t wth a thcker needle accordng
to the materal.
™
Correctly poston the needle and the
shuttle.
™
Wden the dstance between the needle
and the wper. (16 to 18 mm)
16
-
16
131
133
4. Threads
are not
trmmed.
(Bobbn thread
only)
1
The counter knfe s dull.
2
The dfference n level between the
needle hole gude and the counter
knfe s not enough.
3
The movng knfe has been mproperly
postoned.
4
The last sttch s skpped.
5
Bobbn thread tenson s too low.
™
Replace the counter knfe.
™
Increase the bend of the counter knfe.
™
Correct the poston of the movng knfe.
™
Correct the tmng between the needle and
the shuttle.
™
Increase the bobbn thread tenson.
132
132
132
131
18
5. Sttch
skppng
often
occurs.
1
The motons of the needle and shuttle
are not properly synchronzed.
2
The clearance between the needle
and shuttle s too large.
3
The needle s bent.
4
The drver excessvely bends the needle.
™
Correct the postons of the needle and
shuttle.
™
Correct the postons of the needle and
shuttle.
™
Replace the bent needle.
™
Correctly poston the drver.
131
131
16
131