JUKI MO-6000S series Engineer's Manual page 85

Trouble
From the previous page
9. Triangle double chain looper thread stitches
are skipped.
The needle fails to catch the double chain
looper thread.
Needle Viewed from the
wrong side
One stitch is skipped.
Case (1)
Adjustment of looper
Thread tension
Needle guards
Needle heat
The needle point is crushed.
Double chain looper
Adjustment of looper
Thread cam timing
Thread tension
Threading
Case(2)
Clearance or returning amount is not correct.
The thread tension is too high, preventing formation of
good loops.
A needle guard is too high, and loops are crushed. The
clearance is too big, causing the needle to shake.
The thread breaks due to heat generated on the needle,
depending on the type of materials, number of plies,
and sewing speed.
The needle point has been crushed and got thicker and
shorter.
The thread hole in the tip has worn, and the looper
thread does not reach the needle as shown at right.
Excessive return or longitudinal motion will often cause
this stitch skipping.
The thread cam timing is too early, causing the looper
thread to slack before the needle enters a thread
triangle.
The lower thread tension is very low, and the thread is
not stretched.
The area around the thread cam has threaded
erroneously.
Check and Corrective measures
Refer to the related Standard Adjustment.
Reduce the tension. However, be careful not to reduce
the tension too much, othrewise unstable loops will result.
Refer to the relevant Standard Adjustment.
Use a thinner needle. Reduce the sewing speed. Check
the coolant if necessary.
Refer to the clause relating to the needle point crush.
Replace the double chain looper.
Refer to the pertinent Standard Adjustment.
Refer to the pertinent Standard Adjustment.
Increase the thread tension a little.
Correct the threading.
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