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47
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Troubles
Cause (1)
Cause (2)
Checking orders and corrective measures
4.
Thread slips off the needle eyelet at the
sewing start.
5.
Defective stitching tightness at the sewing
start
Length of needle thread remaining at the
top end of needle after thread trimming
varies.
Same cause and corrective measure as “1.
Stitch skipping of 1 to 2 stitches occurs at
the sewing start.”
Needle thread slips off needle eyelet
immediately after thread trimming.
Knotting of needle and bobbin threads at
the sewing start is hard to be performed.
Needle thread tension at the sewing start
is too low.
Tension of thread tension No. 1 is too high
since thread trimming timing is too late, and
thread is trimmed before moving knife
engages with counter knife. (Trimming on
the way)
Depth of thread take-up picker to enter
bobbin case is shallow, and needle thread
slips off thread take-up picker from time to
time.
Sharpening the blade of counter knife is
improper. (Too sharp)
There are scratches on knife thread guide,
moving knife or hook.
Needle is too thick.
Timing is too early, or hook timing is too
late. Moving knife trims the needle thread
since moving knife clamps three threads
before separating threads.
Speed of the sewing machine at the sewing
start is high, and needle and bobbin threads
are hard to be interlaced with each other.
Installation of thread take-up picker is
improper.
Bobbin runs idle and bobbin thread tension
at the sewing start is low.
Bobbin thread tension or needle thread
tension is too low.
Presser foot or throat plate is improper.
Turn OFF the power switch, press by hand thread take-up picker
to bobbin csase at the position where needle is lowered, slowly
turn handwheel by hand to this side, perform thread trimming,
and stop the thread take-up at the upper dead point.
At this time, if the length of needle thread remaining at the top
end of needle is shorter by 10 mm or more than that when
performing thread trimming by pedal operation, the thread is
trimmed on the way. In this case, advance thread trimmer cam
timing, or decrease the tension of thread tension No. 1.
Adjust the thread take-up picker referring to the item (3-12).
Resharpen the counter knife, or replace the counter knife referring
to the item (3-9).
Correct the scratches with buff, or replace the parts.
Replace the needle with a thin one.
If needle thread slips off immediately after thread trimming, it is
because needle thread remaining on the needle is trimmed due
to defective thread separation of the moving knife. In this case,
thread waste of approximately 40 mm falls under throat plate or
under cover.
At this time, delay the thread trimmer cam timing.
Perform one to two stitches of soft start at the sewing start.
Adjust the thread take-up picker referring to the item (3-12).
Adjust the thread take-up picker referring to the item (3-12).
Adjust the tension of the idle-prevention spring of bobbin case.
Increase needle thread tension or bobbin thread tension.
Refer to the previous item [Needle, throat plate and presser foot
used are improper. Presser foot pressure is too low.]
