JUKI MO-6700D Series Manual page 56

Trouble
7. Upper looer thread stitches are skipped.
The needle does not take the
upper looper thread.
Right side Wrong side
Lower
looper
Needle
thread
Upper looper
8. Double chain stitches are skipped.
The double chain looper tails to
catch needle thread loops.
Viewed from the
wrong side
Two stitches
are skipped.
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Case (1)
Threading
Needle height
Needle
Adjustment of the upper looper.
Amount of thread
Needle height
Needle
Double chain looper
Case (2)
The thread has been entangled with a
thread guide.
Threading has not been done correctly.
The needle, if positioned too high or low,
may fail to catch the upper looper thread.
The needle is bent or crushed, in its point.
The height of the blade point is not correct,
making the upper looper unable to properly
pass the thread to the needle.
The clearance between the needle and the
back of the upper looper is not correct.
Excessive upper looper thread is fed,
producing stack of thread.
Needle
Slack of thread
If the needle is not correct, stitch skipping
occurs even when the return of the chain
looper is correct.
The needle is bent or attached with wrong
orientation. A DC x1 needle is used.
The lower part of the blade point has been
deformed, and the blade point fells loops.
Check and Corrective measures
See the threading diagram.
(Refer to the Instruction Manual)
Refer to the related Standard Adjustment
Replace the needle. At this time, be sure to
eliminate the cause for such needle bend or
needle point crush.
Refer to the relevant Standard Adjustment.
Slightly lower the looper thread take-up (left)
(reduction in distance J), or slightly reduce
distance I to decrease the amount of thread.
Make the upper looper thread guide (right)
(shorter decrease in distance K), to reduce the
amount of thread.
Slightly raise the looper thread take-up (right)
(increase in dimension O) to decrease the
amount of thread.
If the thread tension is not enough, increase it.
Refer to the pertinent Standard Adjustment.
Replace the bent needle. (Remove the cause
for the needle bend.) Correct the orientation of
the needle. Use a DC x27 needle (with a better
recess configuration).
Replace the double chain looper.
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