JUKI MO-6000S series Engineer's Manual page 90

Trouble
20. Uneven material feed
21. Puckering
(Mainly concerned with double chain stitch)
Case (1)
Presser foot pressure
Presser foot
Tilt of feed dogs
Height of feed dogs
Adjustment of differential feed
Needle
Thread
Thread tension
Throat plate
Thread cam timing
Feed dogs
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Case(2)
The presser foot pressure is too high.
The hinge is too stiff.
Scratches on or defective finish on the presser foot sole
produce friction between the presser foot and materials.
The front is too high.
A different in level exists between the main feed dog
and differential feed dog.
The differential feed has been improperly adjusted.
The needle is too thick.
The thread used is too thick.
Both the needle thread and looper thread tensions are
too high.
The throat plate has a large needle hole.
The thread cam timing is too late.
The leading edge of the feed dog teeth has been
rounded off.
A difference in level exists between the main feed dog
and differential feed dog.
Check and Corrective measures
Reduce the presser foot pressure except for the uneven
material feed due to packering.
Remove the stiffness provided no hinge play is produced.
Buff the presser foot sole for good surface finish.
Make the front down. However, be sure to align the
differential feed dog with the main feed dog.
Eliminate the difference in level.
Provide differential feed suited to the material.
Use a thin needle as much as possible.
Use a thin needle as much as possible.
Reduce the both thread tensions to a minimum.
Replace the throat plate with one with a small needle hole.
Advance the cam timing. Refer to the related Standard
Adjustment.
Replace the feed dog.
Eliminate such difference in level.
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