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1-14. troubles and corrective measures (Sewing conditions)
Trouble
1. The needle
1 Sttches are slpped at the start.
thread slps off at
the start of bar-
tackng.
2 The needle thread remanng on
3 The bobbn thread s too short.
4 Needle thread tenson at 1st
5 Thread clamp s unstable (mate-
6 Ptch at 1st sttch s too small.
2. Thread often
1 The shuttle or the drver has
breaks or syn-
thetic fiber thread
2 The needle hole gude has
splits finely.
3 The needle comes n contact wth
4 Fbrous dust s n the groove of
5 The needle thread tenson s too hgh.
6 The tenson of the thread take-up
7 The synthetic fiber thread melts due
8 When takng up thread, thread s
3. The needle often
1 The needle s bent.
breaks.
2 The needle comes n contact wth
3 The needle s too thn for the
4 The drver excessvely bends the
4. Threads are not
1 The counter knfe s dull.
trmmed.
2 The dfference n level between
3 The movng knfe has been m-
4 The last sttch s skpped.
(Bobbn thread only)
5 Bobbn thread tenson s too low.
6 Floppng of cloth
7 Ptch of the last sttch s small.
8 Hole of the needle hole gude s
Cause
the needle after thread trmmng
s too short.
sttch s too hgh.
ral s apt to be expanded, thread
s hard to slde, thread s thck,
etc.).
scratches.
scratches.
the work clamp.
the shuttle race.
sprng s too hgh.
to heat generated on the needle.
perced wth needle tp.
the work clamp.
materal.
needle.
the needle hole gude and the
counter knfe s not enough.
properly postoned.
small.
– 103 –
Correctve measures
™ Adjust the clearance between the needle
and the shuttle to 0.05 to 0.1 mm.
™ Set soft-start sewng at the start of
bartackng.
™ 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.
™ Take t out and remove the scratches us-
ing a fine whetstone or buff.
™ Buff or replace t.
™ Adjust the poston of the work clamp.
™ Take out the shuttle and remove the
fibrous dust from the shuttle race.
™ Reduce the needle thread tenson.
™ Reduce the tenson.
™ Use slcone ol.
™ Lower the needle bar heght from the
engraved marker lne by a half of the lne
to as much as the lne.
™ Check the rough state of needle tp.
™ Use the ball-ponted needle.
™ Replace the bent needle.
™ Adjust the poston of the work clamp.
™ Replace t wth a thcker needle accord-
ng to the materal.
™ Correctly poston the needle and the
shuttle.
™ 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.
™ In crease the bobbn thread tenson.
™ Lower the ntermedate presser heght of
the last sttch.
™ Make the clearance between presser
and needle small.
™ Decrease the stroke of the ntermedate
presser.
™ Make the ptch of the last sttch large.
™ Replace the needle hole gude wth one
wth larger hole.
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