JUKI MO-6700D Series Manual page 57

Trouble
From the previous page
9. Triangle double chain looper thread
stitches are skipped.
The needle fails to catch the
double chain looper thread.
Needl
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.
he 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, otherwise
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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