JUKI LK-1900AN Engineer's Manual page 110

Trouble
From the previous page
2. Needle breakage
To the next page
Cause (1)
From the previous page
1-4) Material to be sewn is not
properly stretched.
1-5) Unstable needle thread
clamp
1-6) Threading the needle bar
thread guide is wrong.
1-7) Bobbin runs idle and the
bobbin thread is drawn out.
2-1) Inadequate clearance
between the shuttle driver
and the needle
2-2) Inadequate clearance be-
tween the needle and the
inner hook
2-3) Feed timing is defective.
Cause (2)
3-E) The bobbin thread tension is
excessive.
3-F) The bobbin or bobbin case has
scratches.
5-A) Thread tends to be extended or
sliding efficiency is worse.
5-B) Pitch of 1st stitch is too small.
7-A) Initial positioning of the moving
knife is inadequate.
3-A) Feed timing is slow in regard to
the work pressure.
Check and corrective measures
Adjust the bobbin thread tension.
Polish it with a buff or replace it.
Remove the slack of the material to be
sewn.
Increase the needle thread clamp needle
number to 3 to 4 stitches.
Lower the speed of the 1st stitch. (600 to
1000 sti/min)
Lower the needle thread tension of 1st
stitch.
Increase the pitch of 1st stitch.
Refer to the item "Threading the needle bar
thread Guide".
Use a stronger idling prevention spring.
Adjust the initial position of the moving
knife.
Adjust the clearance between needle and
shuttle driver.
Adjust the clearance between the needle
and the inner hook.
Change the feed timing by the use of the
memory switch.