JUKI LK-1900B series, Engineer'S Manual

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WARNING :
Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine.
Trouble Cause (1) Cause (2) Check and corrective measures
6. Defective thread trim-
ming
6-1) Sharpness of the knife is defective. 1-A) Worn-out of the moving and counter knives. Replace the moving and counter knives.
1-B) Engagement of the moving and counter knives is
defective.
Properly adjust the height and position of the
moving and counter knives.
1-C) Parallel of the blade section of counter knife is de-
fective.
Properly adjust the parallel of the blade section
of counter knife.
1-D) Attaching position of the counter knife is defective. Properly adjust the attaching position of counter
knife.
6-2) Double cutting for the needle thread.
(Thread waste remains inside the
cylinder arm cap.)
2-A) There is a burr on thread spread-
ing section
A
of the moving knife.
The shape of the thread trimmed
becomes and thread
waste remains.
Paying attention to the blade section, polish with
polishing power, or replace the moving knife.
2-B) Shuttle upper spring has scratches. (The shape of
the thread trimmed becomes and thread
waste remains.)
Remove the scratches.
6-3) Moving knife does not spread threads. 3-A) Initial position of the moving knife is maladjusted. Adjust the initial position of the moving knife.
3-B) Thread trimmer cam position is inadequate. Adjust the thread trimmer cam position.
3-C) Position of the shuttle upper spring is defective. Adjust the position of shuttle upper spring.
6-4) Stitch skipping at the final stitch 4-A) Timing of the needle to the inner hook and the
clearance between them are defective.
Adjust the timing and the clearance.
4-B) Work clamp foot is large. Let the beginning of stitch come closer to the
work clamp foot by moving the pattern.
4-C) Loop of the needle thread falls down. Attach the needle with the long groove orienting
slightly to the right (approximately 20°)
6-5) Bobbin thread cannot be cut. 5-A) Bobbin thread tension is low. Strong then the bobbin thread tension.
5-B) Needle hole size of the needle hole guide is large. Replace the needle hole guide with a new one
having a smaller hole diameter.