JUKI MO-6000S series Engineer's Manual page 84

Trouble
7. Upper looer thread stitches are skipped.
The needle does not take the upper looper
thread.
Right side Wrong side
Lower looper
thread
Needle
Upper looper
8. Double chain stitches are skipped.
The double chain looper tails to catch needle
thread loops.
Needle Viewed from the
wrong side
Two stitches
are skipped.
Case (1)
Threading
Needle height
Needle
Adjustment of the upper looper.
Amount of thread
Needle height
Needle
Double chain looper
to the next page
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 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) (shprter
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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