114
12.trouBLES AND CorrECtIVE MEASurES
Phenomenon
Thread
breakage
Sttch skp-
png
Loose sttch
Irregular
sttch tght-
ness
Needle
breakage
Cause
1
When the thread gets entangled n the thread take-
up lever.
2
When the needle thread s threaded n a wrong way.
3
When the thread gets entangled n the sewng hook.
4
When the needle thread s excessvely tght or loose.
5
When the needle thread slps out of the rotary dsc.
6
When the tenson of the thread take-up sprng s
excessvely hgh or low.
7
When the stroke of the thread take-up sprng s ex-
cessvely large or small.
8
When the tmng of the sewng hook and the needle
s not matched.
9
When there s a scratch on the thread path of
hook, bobbn case, thread take-up lever or any
other part.
!0
When the thread s not sutable.
a. The qualty of the thread s poor.
b. The thread s too thck for the needle.
c. The thread s broken by heat.
!1
When the sttch s skpped.
1
When the needle s nserted n a wrong way.
a. The needle s not entrely nserted nto the nee-
dle bar.
b. The needle eye s not facng straght to the op-
erator.
c. The needle s facng backwards.
2
When the needle tself s not sutable.
a. The needle s bent.
b. The qualty of the needle s not good.
c. The needle s too thn for the thread.
d. Blunt needle s used.
3
When the hook blade pont s not sharp enough or
damaged.
4
When the tmng of the sewng hook and the needle
s not matched.
5
When the heght of the needle bar s not correct.
6
When the clearance between the needle and the
sewng hook s too great.
7
When the needle thread slps out of the rotary
dsc.
(For auxlary thread take-up lever type only)
1
When the needle thread tenson s too low.
2
When the tenson of the thread take-up sprng s
too low.
3
When the tenson of the bobbn thread s too hgh.
4
When the tmng of the sewng hook and the needle
s not matched.
5
When the thread s too thck for the needle.
6
When the thread slps out of the rotary dsc.
1
When the bobbn thread tenson s too low.
2
When the bobbn thread s not wound correctly.
3
When there s a scratch on the thread path of the
sewng hook, bobbn case, thread take-up lever or
any other parts.
1
When the needle s bent.
2
When the qualty of the needle s not good.
3
When the needle s not entrely nserted nto the
needle bar.
4
When the needle hts the sewng hook.
5
The needle s too thn for the sewng materal and
thread.
6
The needle hole n the throat plate s too narrow.
7
The needle hts aganst the throat plate.
8
The needle hts aganst the presser foot.
Correctve measures
Remove the entanglement.
Thread t correctly.
Remove the entanglement.
Adjust the thread tenson.
Increase the tenson of the pretenson dsk.
Adjust the tenson of the take-up sprng.
Adjust the stroke of the take-up sprng. (8 to 12
mm)
Adjust the tmng.
Remove such a scratch or replace the compo-
nent.
Use a thread of good qualty.
Use a sutable thread or needle.
Use JUKI Slcone Ol Lubrcant unt.
Refer to the followng paragraphs, Sttch skppng.
Fully nsert the needle.
Let the needle eye face straght to the operator.
Let the long groove on the needle face to the op-
erator.
Replace t wth a new needle.
Use a needle of good qualty.
Use a sutable needle or thread.
Replace t wth a new needle.
Resharpen the hook or replace t.
Adjust the tmng properly.
Adjust the heght of the needle bar.
Adjust the clearance.
Adjust the poston of the auxlary thread take-up
lever properly.
Increase the needle thread tenson.
Increase the tenson of the sprng.
Decrease the bobbn thread tenson.
Adjust the tmng correctly.
Use a sutable needle or thread.
Increase the tenson of the pretenson dsk.
Increase the bobbn thread tenson.
Wnd up the bobbn thread evenly.
Remove such a scratch or replace the compo-
nent.
Replace t wth a new needle.
Use a needle of good qualty.
Insert the needle nto the needle bar as far as t
wll go.
Adjust the tmng and clearance between the
needle and the sewng hook and also the pos-
ton of the needle guard.
Replace a sutable needle.
See page
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