JUKI MO-6800S Series Engineer's Manual page 39

Adjustment procedures
1) Adjusting the thread cam
1. Adjust the position of the thread cam ❽ by its setscrew ❶ with
the needle  at their upper dead point so that the straight section
of the thread cam ❽ is leveled.
2. Laterally position the thread cam ❽ so that the thread cam nail ❻
is located at the center of groove A of the thread cam ❽ .
[How to check for proper positioning]
Check that the thread cam ❽ releases the looper thread when the
needle  tip begins to come out of the bottom surface of the throat
plate  by 1 to 2 mm.
2) Adjusting the thread cam thread guides A and B and the
thread cam nail
1. Install looper thread cam thread guides A ❷ and B ❸ to the direc-
tion B until the full length of the elongated hole with setscrews A
❹ and B ❺ .
⊕ means to have more thread amount while sewing.
⊖ means to have less thread amount while sewing.
2. Install thread cam nail ❻ with setscrew ❼ so that the straight
section of the forked portion is leveled.
3) Positioning the chain looper thread guide
1. Fix the chain looper thread guide  by the setscrew  so that a
thread path provided between the double chain looper  and the
thread cam thread guide base ❾ is straight line.
Results of Improper adjustment
If the timing of the thread cam
o
❽ is too early, the needle  tip
will fail to enter a thread triangle,
resulting in looper thread stitch
skipping.
If the timing of the thread cam
o
❽ is too late, puckering and
loose looper thread stitches will
results.
If the thread cam thread guide is
o
moved away from you, the take-
up amount of the lower looper
thread will decrease. In this
case, puckering may result there
by impairing the feeling of the
finished product.
In the case the looper thread
o
is not appropriately adjusted,
thread loops cannot be formed
with consistency. (Thread can be
excessively loosened or thread
loops cannot be formed.)
If a thread path has not been
o
straight line, stitch perforation
becomes unstable. Also, looper
thread is caught by the thread
guide base stopper  .
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