JUKI MS-3580 Serie Manual De Instrucciones página 120

Trouble
2. Thread cut at bobbin
thread looper
3. Needle breakage
Cause (1)
2-1) Thread path
2-2) Adjustment of looper
thread cam
2-3) Thread tension
2-4) Thread
2-5) Needle heat
3-1) Needle entry
3-2) Interference between
lower looper and blin
dstitch of needle
3-3) Interference between
rear of lower looper
and needle tip
3-4) Rear needle guard
3-5) Needle size
3-6) Thread tension
3-7) Feed dog height
Cause (2)
1-A) Resistance is developed
when there is a scratch, a
burr, or rust on the throat
plate, lower looper, looper
thread cam, looper thread
path pipe, looper thread
path guide, or thread
tension disc.
2-A) Excessive tension is
provided because of
improper timing of the
looper thread cam.
3-A) Excessive thread tension
4-A) Poor quality of the thread
5-A) Thread cut occurs when
the thread touches the
right needle at sewing
stop due to needle heat.
1-A) Front/rear and right/left needle
entry seems to be awkward
in conjunction with the needle
hole of the throat plate.
2-A) The needle breaks
because of the
interference between the
tip of the lower looper
and the needle.
3-A) The needle breaks
because of the strong
interference between the
rear of the lower looper
and the needle tip.
4-A) Excessive clearance
between the needle and
rear needle guard causes
needle shaking and then
interference between
the needle and the lower
looper tip resulting in
needle breakage.
5-A) For the case that the
needle is too thin for the
material that is now used
6-A) Excessive needle
thread tension
7-A) Too high feed tooth
causes needle sidewise
movement resulting in
needle breakage.
− 48 −
Check and corrective measures
Take measures to remove fl aws, burrs,
etc., and fi nish the thread path neatly.
In this case, however, the throat plate,
lower looper, looper thread cam, and such
important parts should be replaced if their
shapes seem to have changed.
Refer to the standard adjustment values.
Reduce the tension in consideration of the
tension balance with the needle thread.
Use a high-quality thread.
Reduce the sewing speed.
Refer to the standard adjustment values.
Adjust the lower looper to prevent the
interference.
Refer to the standard adjustment values.
$- 6. Adjust the looper movement locus.
Refer to the standard adjustment values.
Adjust the clearance between the needle
and rear needle guard.
Refer to the standard adjustment values.
Use a thicker needle.
Reduce the needle thread tension.
Refer to the standard adjustment values.