JUKI MO-6700D Series Manual page 53

Trouble
2. Looper thread breakage
3. Needle breakage
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Case (1)
Thread path
Adjustment of the looper thread take-up
Thread tension
Thread
Position of the thread guides
(only for double chain stitch)
Double chain looper avoid
Needle heat
Needle entry
Upper looper position
Contact with the looper
Case (2)
Scratches, burrs, rust, etc, on the paw of
the throat plate, stitch tongue, looper,
looper thread take-up, thread guide,
or tension discs causes friction.
The looper thread take-up or thread guide
has been improperly positioned, causing
excessive thread tension.
The looper thread tension is too high.
The thread is weak because of its poor
quality.
The upper looper thread guide is too high,
and the thread taking balance is disturbed,
resulting in the thread breakage.
The double chain looper strikes the needle
at the back, causing the thread breakage.
The needle gets hot, and the looper thread
breaks when it comes in contact with the
hot needle at the time of needle stop.
The needle entry has not been correctly
adjusted, and the needle strikes the throat
plate or presser foot.
The upper looper juts out too much or
it is too low.
The needle strikes the looper, resulting
in needle breakage.
Check and Corrective measures
Remove such scratches, burrs, etc. and carry
out thread path finishing. Replace loopers or
other components which have been deformed,
causing thread breakage.
Refer to the pertinent Standard Adjustment.
Reduce the tension while checking the tension
balance other looper thread.
Replace the thread by one with good quality.
Refer to the pertinent Standard Adjustment.
Correct the longitudinal motion of the double
chain looper so as not to cause the looper to
strike the needle.
Refer to the clause relating to the needle heat
causing needle thread breakage.
Correct the needle entry.
Refer to the related Standard Adjustment.
Re-position the looper so that it does not come
in contact with the needle. Adjust the longitudinal
motion of the double chain looper for the contact
of its back with the needle.
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