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Trouble
From the previous page
2-3) The needle thread slips
2-4) Knot tying between the
3. The thread tension is
3-1) The tension of the needle
inappropriate at sewing
start.
4. The needle thread is un-
4-1) Stitch skipping at the final
trimmed. (But the bobbin
thread is trimmed.)
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Cause (1)
3-A) Too early cam timing or too late hook
off the needle immediate-
ly after thread trimming.
4-A) The sewing speed at sewing start is
needle and bobbin threads
is not easy at sewing start.
1-A) Bobbin idling causes the bobbin thread
thread is too low at sew-
ing start.
1-B) The tensions of the bobbin thread and
1-C) The presser or throat plate is inappro-
1-A) The needle is inappropriately mount-
stitch occurs.
1-B) The stroke of the thread take-up spring
1-C) The hook is inappropriately adjusted.
Cause (2)
timing causes the moving knife to cut
the needle thread to hold 3 threads
before thread separation.
too fast to knot the needle and bobbin
threads together.
tension at sewing start to decrease.
needle thread are too low.
priate.
ed.
is too long.
Check and corrective measures
Slipping of the needle thread from the needle immedi-
ately after thread trimming results from cutting the nee-
dle thread passing though the needle due to defective
thread spreading by the moving knife. In such a case,
Thread chips of 40 mm level exist under the throat
plate or on the underside cover. In this case, delay the
timing of the thread trimming cam.
Conduct 1 or 2 stitches of soft-start (800 sti/min) at the
sewing start.
Adjust the hook thread presser in accordance with 3.-
(9)-7.
Increase the tensions of the bobbin thread and needle
thread.
Refer to the previous item, [An inappropriate needle,
throat plate, or presser is used. Alternatively, he pres-
sure of the presser is too low].
Mount a needle appropriately and make sure that the
needle is not bent.
Shorten the stroke of the thread take-up spring. (5 to 7
mm)
Check for stitch skipping at low sewing speed, and re-
adjust the hook timing (Hasten the timing of the hook.).
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