JUKI MO-6700D Series Manual page 55

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
oopers 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 Instruction Manual)
Refer to the threading diagram.
(Refer to the Instruction Manual)
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.
Page
4, 8
36
8, 14
36
36