1
22.
TROUBLES AND CORRECTIVE MEASURES
CAUSES
1
CORRECTIVE MEASURES
I
1
Needle
breaking
i
I
I) Needle type is wrong.
!
(2)
h'eedle size is not correct.
I
(3)
Needle
is
not installed correctly.
i4)
Needle is not straight.
(5)
Keedle-to-needle guard relation is bad
-
1
t
61 Needle-to-looper relation
IS
bad.
T---..
2,
cloth
Is
not cut
(I)
Position of the upper and lower knife is
I
inadequate.
/
(21
Knife blade has worn out
,3
Use a specified needle.
0
Use a needle size suitable to the thread gauge
and type of fabrics.
3
Install the needle correctly (See
8).
0
Use a straight needle.
0
Correct the relation (See
2
1
).
c
Correct the needle to looper relation (See 15).
~
-
.
--
~
~
-
Adjust the knife position (See 20).
0
Sharpen the lower knife or renew the upper
knife.
3.
Stitch skipping
4.
Thread breaking
(
I
)
Needle-to-looper relation is wrong.
(2)
Looper blade is blunt.
(3)
Needle is threaded with S-twist (or left-
hand twist) thread.
(4) Thread tension is wrong.
(5)
Double chain looper thread tension is not
enough.
(
1
)
Quality of the thread is poor.
(2)
Thread is too thck for the needle size.
(3) Needle is installed in a wrong way.
(4)
Thread tension is too high.
(5) There is a scratch or bruise on the surface
of needle, looper, throat plate or needle
guard.
0
Correct the needle-to-looper relation (See
15).
0
Correct the shape of the looper blade using
an oilstone, or replace it.
0
Use a Z-twist (or right-hand twist) thread witb
the needle.
0
Adjust the thread tension (See 10).
0.
Correct the position of the chain looper threa~
cam (See 18).
0
Use a thread of good quality.
0
Select a suitable needle or thread.
0
Install the needle correctly (See 8).
0
Adjust the thread tension
0
Remove scratches and bruises using an oil-
stone or buffing machine.
5.
Double chain-off
thread
stitcfung
failure
(MOG-25
16N)
6.
Puckering
7.
Irregular stitching
(I) Presser foot does not evenly act on the feed
dog.
(
2) Rear presser is shaking.
(3)
Needle thread and looper thread tensions
are not correct.
(4) Double chain looper is installed in a wrong
way
(
1
)
Needle is too thick
Thread tension is too high.
Pressure applied by the presser foot is too
high
or
too low.
Feed dog comes up too much from the
throat plate surface.
(5)
Knife fails to cut the fabrics sharply.
(6) Differential feed mechanism is not set
correctly.
(
1
)
Thread is not supplied smoothly.
1
0
Correct the relation of the presser foot with
the feed
dog.(See 17).
0
Adjust the rear presser for smooth and
steady motion.
0
Adjust the thread tension (See
10).
0
Correct the double chain looper (see 15).
0
Select a suitable needle size for the thread
and materials.
0
Adjust the thread tension.
0
Correct the presser foot pressure (See
1
1
).
0
Lower the feed dog.
0
Sharpen the lower knife.
0
Correct the differential feed mechanism
(See 16).
0
Use smooth thread with even thickness or
(2)
Thread tension is too low.
(3) Needle is blunt.
(4) Pressure applied by the presser foot is
inadequate.
(5)
Height of the feed dog is wrong.
clean up the thread path.
0
Increase the thread tension.
0
Use a new needle.
0
Adjust the presser foot pressure (See 11).
0
Adjust the height of the feed dog (See 17).
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