Troubles And Corrective Measures; With Regard To Sewing - JUKI LU-2800 Series Engineer's Manual

8. Troubles and corrective measures

(1) With regard to sewing

WARNING :
Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine.
Trouble
1. Thread breakage
2. Thread is worn out.
Cause
1-1) Thread path, needle point, hook blade
point or innerhook resting groove on
the throat plate has sharp edges or
burrs.
2-1) Needle thread tension is too high.
2-2) Needle comes in contact with the
blade point of hook.
2-3) Clearance of opener is too large.
2-4) Amount of oil in the hook is insuffi-
cient.
2-5) Trimmed with the tooth of the feed
dog.
Checking
1-A) Check the sharp edge or burr
on the respective parts.
2-A) Check the clearance.
3-A) Check the clearance.
4-A) Check the amount of oil in the
hook.
5-A) Check the feed dog.
5-B) Check the alternate vertical
movement.
5-C) Check the sewing speed.
Corrective measures
Remove the sharp edges or burrs on the blade
point of hook using a fine emery paper.
Buff up the groove section on the throat plate.
Replace the needle with a new one.
Adjust the needle thread tension.
Refer to "2.-(6) Needle-to-hook timing".
Decrease the clearance.
Refer to "2.-(5) Adjusting the opener".
Adjust the amount of oil in the hook.
Refer to "2.-(15) Lubrication".
Provide a groove behind the feed dog needle hole.
Reduce the amount of alternate vertical move-
ment.
Reduce the sewing speed.