JUKI MO-6800S Series Engineer's Manual page 58

WARNING :
Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine.
Trouble
From the previous page
2. Looper thread breakage
Cause (1)
1-10) Deffective double 10-A) Refer to the clause referring to defective
chain-off thread
(only for double
chainstitch)
1-11) Threading 11-A) The thread is entangled with the thread
2-1) Thread path 1-A)
2-2) Adjustment of the 2-A)
looper thread take-
up
2-3) Thread tension 3-A)
2-4) Thread 4-A)
2-5) Position of the 5-A)
thread guides
2-6) Double chain looper 6-A)
avoid (only for dou-
ble chainstitch)
2-7) Needle heat 7-A)
Cause (2)
double chain-off thread.
guide, or the looper has been incorrect-
ly threaded.
Scratches, burrs, rust, etc, on the paw
of the throat plate, stitch tongue, looper,
looper thread take-up, thread guide, or
tension discs causes friction.
The looper thread take-up or thread
guide has been improperly positioned,
causing excessive thread tension.
The looper thread tension is too high.
The thread is weak because of its poor
quality.
The upper looper thread guide is too
high, and the thread taking balance is
disturbed, resulting in the thread break-
age.
The double chain looper strikes the
needle at the back, causing the thread
breakage.
The needle gets hot, and the looper
thread breaks when it comes in contact
with the hot needle at the time of needle
stop.
Checking order and adjusting procedure
Refer to the treading diagram.
Remove such scratches, burrs, etc. and carry out
thread path finishing. Replace loopers or other
components which have been deformed, causing
thread breakage.
Refer to the pertinent Standard Adjustment.
Reduce the tension while checking the tension
balance other looper thread.
Replace the thread by one with good quality.
Refer to the pertinent Standard Adjustment.
Correct the longitudinal motion of the double
chain looper so as not to cause the looper to
strike the needle.
Refer to the clause relating to the needle heat
causing needle thread breakage.