JUKI LU-2800 Series Engineer's Manual page 128

WARNING :
Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine.
Trouble
6. Loose stitches (Needle thread
rises.)
7. Irregular stitches
8. Loose stitches at the time of
corner stitching
Adjustment of the thread take-up spring
Decrease the tension of the thread take-up spring and decrease the stroke of the spring to improve irregular stitches.
o
Cause
6-1) Needle thread has not been fully
pulled up.
7-1) Stroke of the thread take-up spring is
improper.
7-2) Thread paths have been poorly fin-
ished.
7-3) Bobbin fails to move smoothly.
7-4) Bobbin thread tension is too low.
7-5) Bobbin has been wound too tight or
too weak.
7-6) Direction of setting bobbin is reverse.
8-1) Needle thread on the stopping side is
drawn out more than is necessary.
Checking
1-A) Check the stroke of the thread
take-up spring.
2-A) Check the finish of the respec-
tive thread paths.
3-A) Check the change of bobbin
thread tension.
5-A) Check the state of bobbin wind-
ing.
6-A) Check the setting.
1-A) Check the stroke of the thread
take-up spring.
1-B) Check the hook timing.
Corrective measures
Increase the needle thread ension.
Use the optional walking foot. (Top-divided type)
Adjust the thread take-up spring to move to ap-
proximately 1 mm from the initial position when
hook draws thread maximumly.
Finish with a fine emery paper or buff.
Replace the bobbin or the hook with new ones.
Increase the tension of the bobbin thread.
Decrease or increase the tension applied to the
bobbin winder.
Properly set the bobbin.
In crease the stroke of the thread take-up spring.
Retard the hook timing.
Use the optional walking foot. (Top divided type)