JUKI LU-2800 Series Engineer's Manual page 130

WARNING :
Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine.
Trouble
2. Thread slips off the 2-1) Needle thread slips off the needle eye-
needle eyelet. let immediately after thread trimming.
2-2) Needle thread slips off the needle eye-
let at the start of sewing.
3. Defective thread 3-1) Thread cannot be trimmed.
trimming
3-2) Thread remains uncut after thread trim-
ming.
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Cause
1-A) Check whether the needle thread re-
maining at the needle top after thread
trimming is short.
2-A) Check whether the needle thread re-
maining at the needle top at the start of
sewing is short.
2-B) Hard-to-slip thread is used.
1-A) The blades of moving knife and counter
knife have been improperly adjusted.
1-B) The blades of moving knife and counter
knife have worn out or broken.
1-C) Pressure of the counter knife is insuffi-
cient.
1-D) Presser foot drops from cloth at the time
of thread trimming.
2-A) The blades of moving knife and counter
knife have been improperly adjusted.
2-B) The blades of moving knife and counter
knife have worn out or broken.
2-C) Thread trimmer timing is excessively
retarded.
2-D) Pressure of the counter knife is insuffi-
cient.
2-E) Presser foot drops from cloth at the time
of thread trimming.
Checking
Refer to the cause of previous section "Needle
thread remaining at the needle top after thread trim-
ming is short".
Decrease the number of times of threading needle
thread.
Refer to "2.-(16)-6) Adjusting the knife pressure" and
"2.-(16)-1), 2) and 3) Position of the moving knife
and Position of the counter knife".
Replace the moving knife and counter knife with new
ones.
Refer to "2.-(16)-6) Adjusting the knife pressure".
Perform thread trimming on cloth.
Refer to "2.-(16)-6) Adjusting the knife pressure" and
"2.-(16)-1), 2) and 3) Position of the moving knife
and Position of the counter knife".
Replace the moving knife and counter knife with new
ones.
Refer to "2.-(16)-4) Thread trimmer cam timing".
Refer to "2.-(16)-6) Adjusting the knife pressure".
Perform thread trimming on cloth.
Corrective measures