JUKI LK-1900AN Engineer's Manual page 113

Trouble
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5. Thread breakage at the time of
thread trimming
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Cause (1)
4-4) Clearance between the
shuttle driver and the inner
hook is too small.
4-5) Scratches on the needle
hole guide.
4-6) Finish of the needle hole is
rough.
4-7) Thread take-up spring is
maladjusted.
4-8) Rotation of the inner hook
is defective.
4-9) Needle thread clamp OFF
5-1) Thread release timing is
defective.
5-2) Thread spreading section
of the moving knife has
scratches.
5-3) Shuttle upper spring has
scratches.
5-4) Level difference between
the needle hole guide and
the counter knife is too high.
Cause (2)
7-A) Stroke of the thread take-up
spring is too large.
7-B) Thread take-up spring tension is
too high.
8-A) Race face of the shuttle is
clogged with thread waste.
8-B) Oil amount is insufficient.
9-A) Needle thread length is inad-
equate.
1-A) Floating amount of the thread
tension disk No. 2 is small.
4-A) Thread is cut before trimming
with the blade section of the
moving knife.
Check and corrective measures
Properly adjust the clearance between the
shuttle driver and the inner hook.
Remove the scratches and polish with buff,
or replace the needle hole guide.
Replace the needle.
Properly adjust the thread take-up spring.
Properly adjust the thread take-up spring.
Remove the inner hook and remove the
thread waste.
Supply oil to the shuttle components.
Adjust the needle thread length and turn
the needle thread clamp ON.
Adjust the amount of thread tension No. 2
floating.
Paying attention to the blade section, polish
with polishing powder.
Remove the scratches.
Properly adjust the position of counter
knife.