28.
TROUBLES
AND
CORRECTIVE
MEASURES
Trouble
Cause
Corrective
measures
Page
1.
The
needle
thread
slips
off
the
needle
at
the
start
of
bar-
tacking.
0 Stitches are skippedat the start.
0 The needlethread remainingon the
needle
after
thread
trimming
is
too
short.
0 The bobbin thread is too short.
0 The feedtimingis bad.
o
Adjust
the
clearance
between
the
needle
and
the
shuttle
to
0.05
to
0.1mm.
o
Correct
the
thread
tension
release
timing
of
the
thread
tension
controller
No.
2.
o
Increase
the
tension
of
the
thread
take-up
spring,
or
decrease
the
tension
of
the
thread
tension
controller
No.
1.
o
Decrease
the
tension
of
the
bobbin
thread,
o
Increase
the
clearance
between
the
needle
hole
guide
and
the
counter
knife,
o
Correct
the
feed
timing.
7
7
6
6
8
•6
2.
Thread
often
breaks
or
synthetic
fiber
thread
splits
finely.
0 The shuttle or the driver has scratches.
0 The needlehole guidehasscratches.
0 The needlestrikes the work clampfoot.
0 Fibrousdust isin the
groove
of the
shuttle
race.
0 The needle thread tension is too high.
0 The tension of the thread take-up spring
is
too
high.
0 Thesynthetic fiber thread melts due to
heat
generated
on
the
needle.
o
Take
it
out
and
remove
the
scratches
using
a
fine
whetstone
or
buff.
O
Buff
or
replace
it.
o
Correct
the
position
of
the
work
clamp
foot.
o
Take
out
the
shuttle
and
remove
the
fibrous
dust
from
the
shuttle
race.
o
Reduce
the
needle
thread
tension.
o
Reduce
the
tension.
O
Use
silicone
oil.
8
7
6
6
4
3.
The
needle
often
breaks.
0 The needle is bent.
0 The
needle
hitsthe work
clamp
foot.
0 The feed timingis bad.
0 The
needle
istoo thinforthe
material.
0 The driverexcessively bends the needle.
o
Replace
the
bent
needle,
o
Correct
the
position
of
the
work
clamp
foot.
o
Correct
the
feed
timing,
o
Replace
it
with
a
thicker
needle
according
to
the
material,
o
Correctly
position
the
needle
and
the
shuttle.
5
8
6
4
7
4.
Threads
are
not
trimmed.
0 The counter knife is dull.
0 The difference in levelbetween the needle
hole
guide
and
the
counter
knife is
not
enough.
0 The movingknife has been improperly
positioned.
0 Thelaststitch isskipped.
o
Replace
the
counter
knife,
o
Increase
the
bend
of
the
counter
knife.
o
Correct
the
position
of
the
moving
knife.
o
Correct
the
timing
between
the
needle
and
the
shuttle.
8
8
8
7
S.
Stitch
skipping
often
occurs.
0 The motions of the needle and shuttle
are
not
properly
synchronized.
0 The clearance between the needle and
shuttle
is
too
large.
0 The needle is bent.
0 The feed timing is bad.
0 The driver excessively bends the needle.
o
Correct
the
positions
of
the
needle
and
shuttle.
o
Correct
the
positions
of
the
needle
and
shuttle,
o
Replace
the
bent
needle,
o
Correct
the
feed
timing,
o
Correctly
position
the
driver.
7
7
5
7
6.
The
needle
thread
comes
out
on
the
wrong
side
of
the
material.
0 The needle thread tension is not high
enough.
0 The tension release mechanism failsto
work
properly.
0 The needle thread after thread trimming
is
too
long.
o
Increase
the
needle
thread
tension.
o
Check
whether
or
not
the
tension
disc
No.
2 is
released
during
bar-tacking,
o
Increase
the
tension
of
the
thread
tension
controller
No.
1.
6
7
6
7.
Threads
break
at
time
of
thread
trimming.
0 The movingknife has been improperly
positioned.
o
Correct
the
position
of
the
moving
knife.
8
-11-
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