JUKI MO-6000S series Engineer's Manual page 83

Trouble
From the previous page
6. Lower looper stitches are skipped.
The upper looper does not catch the lower
looper thread.
Right side Wrong side
Case (1)
Height of needle
Needle heat
Positioning of the needle thread take-up guide and
needle thread guide
Threading
Threading
Upper looper
Lower looper
Adjustment of the loopers
Thread amount
Case(2)
The needle has incorrect height and does not properly
pick up loops even if the looper has a correct return.
Stitch skipping occurs before the thread breaks due to
needle heat.
They are positioned too high, and the needle thread
take-up takes too much thread, producing too small
loops.
The thread has been entangled with a thread guide.
The reading has bot been correctly done.
The thread has been entangled with a thread guide.
Threading has not been done correctly.
The blade point has a bad shape, and fails to catch the
loops.
The clearance between the needle and the back of lower
looper are not correct.
The feed amount of the lower looper, height of the upper
looper, or clearance produced at time of crossing of the
upper and lower loopers is not correct.
Too much lower looper thread is fed, giving slack of
thread.
Check and Corrective measures
Refer to the related Standard Adjustment.
Refer to the clause relating to the needle thread breakage
due to needle heat.
Refer to the pertinent Standard Adjustment.
See the threading diagram.
Refer to the threading diagram.
Replace the upper looper with badly deformed blade point.
Replace the lower looper having a deformed tip.
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.
Slightly raise the looper thread take-up (right) (increase
in dimension O) to decrease the amount of thread.
Lower the lower looper thread guide (increase in distance
L), and decrease distance N to reduce the amount of
thread.
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