JUKI LZ-2280N SERIES Engineer's Manual page 35

Adjustment Procedures
1) Loosen nut 3 in the knife driving arm 7 , and adjust the initial
position of the moving knife.
Loosen/tighten nut 3 after roller 4 has fitted in the groove on
the thread trimming cam 8 by pressing roller arm 6 with
fingers. This will prevent knife driving arm 7 from moving out
of position thereby allowing you to perform the adjustment in
safety.
2) After adjusting the initial position of the moving knife, turn the
handwheel in the state that roller 4 has fitted in the groove on
the thread trimming cam 8, and check that the latch has
securely entered when the moving knife moves forward or
backward until it will go no further. (You can hear "click" when
the latch has entered.)
(Caution) When a feed dog other than that which is delivered
as standard is used, there is a case where the feed dog
interferes with counter knife according to its shape. In case
of interference, move the feed dog to the left side from the
engraved dot and check that there is no interference with
each other.
Adjustment Procedures
If the timing of the thread trimming cam is not correct, adjust it in
the following steps of procedure.
1) Loosen two screws 5 in the cam.
2) Turn the main shaft handwheel until the red marker dot
engraved on the handwheel is aligned with the marker dot
engraved on the machine arm.
3) Push roller arm 6 until roller 4 fits in the groove in thread
trimming cam 8. Lightly push thread trimming cam 8 on the
handwheel side and turn it in the reverse direction until it will
go no further. Now, tighten two screws 5 in the cam.
Results of Improper Adjustment
™ If the initial position of the moving
knife is not properly adjusted, the
moving knife will fail to cut the
thread or cut the thread at a
wrong position reducing the
length of remaining thread after
thread trimming.
Results of Improper Adjustment
™ If the timing of the thread
trimming cam is excessively
advanced, the knife will fail to cut
the thread or the length of the
thread remaining after thread
trimming will be decreased
resulting in slip-off of the thread.
™ If the timing of the thread
trimming cam is excessively
retarded, the knife will fail to cut
the thread or the moving knife
will fail to fully return to the home
position making the moving knife
projects at the start of sewing.
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