Sewing Conditions - JUKI LK-1900AN Engineer's Manual

(2) Sewing conditions

Trouble
1. Thread comes off at the start of
sewing.
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Cause (1)
1-1) Stitch skipping at the 1st
stitch
1-2) Length of thread remaining
at the needle is not sufficient.
1-3) Length of bobbin thread
remaining is not sufficient.
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Cause (2)
1-A) Penetration resistance of the
thread against the cloth is small.
2-A) Tension controller No. 1 provides
an excessive tension.
2-B) Floating of the AT thread tension
disc is insufficient.
2-C) Stroke of the thread take-up
spring is excessive.
2-D) The thread take-up spring ten-
sion is insufficient.
2-E) Level difference between the
needle hole guide and the coun-
ter knife is excessively high.
2-F) Needle thread tension is high and
the thread is excessively stretched.
2-G) Thread spreading section of the
moving knife has scratches.
3-A) Level difference between the
needle hole guide and the coun-
ter knife is excessively high.
3-B) Lower face of the needle hole
guide has scratches.
3-C) Thread spreading section of the
moving knife has scratches.
3-D) Shuttle upper spring has scratch-
es.
Check and corrective measures
Decrease the sewing speed at the start of
sewing.
Use a thinner needle. (Lower the needle
count to be used.)
Properly adjust the tension controller No. 1.
Adjust the amount of AT thread tension
floating.
Adjust the stroke of the thread take-up
spring.
Adjust the thread take-up spring tension.
Adjust the height of the counter knife.
Adjust the needle thread tension.
Polish the thread spreading section of the
moving knife with buff or replace the knife.
Adjust the height of the counter knife. (Oth-
erwise, widen the gap.)
Polish the needle hole guide with a buff or
replace it.
Polish the thread spreading section of the
moving knife with buff or replace the knife.
Polish the shuttle upper race with a buff or
replace it.