Troubles And Corrective Measures (Sewing Conditions) - JUKI LK-1901AN Instruction Manual

8. Troubles and corrective measures (sewing conditions)
Trouble
. The needle thread 1 Stitches are slipped at the start.
slips off at the start
of bar-tacking.
2 The needle thread remaining on
3 The bobbin thread is too short.
4 Needle thread tension at st
5 T h r e a d c l a m p i s u n s t a b l e
6 Pitch at st stitch is too small.
2. T h r e a d o f t e n 1 The shuttle or the driver has
breaks or synthetic
fiber thread splits 2 T h e n e e d l e h o l e g u i d e h a s
finely.
3 The needle strikes the work
4 Fibrous dust is in the groove of
5 The needle thread tension is too
6 The tension of the thread take-
7 The synthetic fiber thread melts
3. The needle often 1 The needle is bent.
breaks. 2 The needle hits the work clamp
3 The needle is too thin for the
4 The driver excessively bends the
5 Needle thread is stepped on by
4. Threads are not 1 The counter knife is dull.
trimmed. 2 The difference in level between
3 Th e m o v i n g k n i fe h as b e e n
4 The last stitch is skipped.
(Bobbin thread only) 5 Bobbin thread tension is too low.
5. S t i t c h s k i p p i n g 1 T h e m o t i o n s o f t h e n e e d l e
often occurs.
2 The clearance between the
3 The needle is bent.
4 The driver excessively bends the
Cause
the needle after thread trimming
is too short.
stitch is too high.
(material is apt to be expanded,
thread is hard to slide, thread is
thick, etc.).
scratches.
scratches.
clamp foot.
the shuttle race.
high.
up spring is too high.
due to heat generated on the
needle.
foot.
material.
needle.
the work clamp foot at the start
of sewing. (Needle bend)
the needle hole guide and the
counter knife is not enough.
improperly positioned.
and shuttle are not properly
synchronized.
needle and shuttle is too large.
needle.
－
Corrective measures
™ Adjust the clearance between the needle
and the shuttle to 0.05 to 0. mm.
™ Set soft-start sewing at the start of
bartacking.
™ Correct the thread tension release timing
of the thread tension controller No. 2.
™ Increase the tension of the thread take-
up spring, or decrease the tension of
the thread tension controller No. .
™ Decrease the tension of the bobbin
thread.
™ Increase the clearance between the
needle hole guide and the counter knife.
™ Decrease the tension at st stitch.
™ Decrease the number of rotation at st
stitch at the sewing start. (Extent of 600
to ,000 sti/min)
™ Increase the number of stitches of
thread clamp to 3 to 4 stitches.
™ Make the pitch at st stitch longer.
™ Decrease the needle thread tension at
st stitch.
™ Take it out and remove the scratches
using a fine whetstone or buff.
™ Buff or replace it.
™ Correct the position of the work clamp
foot.
™ Take out the shuttle and remove the
fibrous dust from the shuttle race.
™ Reduce the needle thread tension.
™ Reduce the tension.
™ Use silicone oil.
™ Replace the bent needle.
™ Correct the position of the work clamp
foot.
™ R e p l a c e i t w i t h a t h i c k e r n e e d l e
according to the material.
™ Correctly position the needle and the
shuttle.
™ Widen the distance between the needle
and the wiper. (23 to 25 mm)
™ 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.
™ Correct the positions of the needle and
shuttle.
™ Correct the positions of the needle and
shuttle.
™ Replace the bent needle.
™ Correctly position the driver.
55
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