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Trouble
From the previous page
1-5) Knot tying between
2. The needle thread slips
2-1) The length of the needle
off the needle at the sew-
ing start.
2-2) The cause and measures
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Cause (1)
5-A) The sewing speed at sewing start is
the needle and bobbin
threads is not easy at
sewing start.
5-B) If the thread trimming speed is fast,
1-A) Too high 1st thread tension due to
thread passing through
the needle varies after
thread trimming.
2-A) The blade of the counter knife has been
are the same as those for
the item, "1. Skipping of
one or more stitches oc-
curs at the start of sewing".
2-B) The knife thread guide, moving knife,
2-C) The needle is too thick.
Cause (2)
too fast to knot the needle and bobbin
threads together.
thread is cut short at thread trimming.
delayed thread trimming timing causes
the thread to be cut before engage-
ment between the moving and counter
knives. (midway cut)
sharpened excessively, and thread is
trimmed only by the counter knife.
or hook has a flaw.
Check and corrective measures
Conduct 1 or 2 stitches of soft-start (800 sti/min) at the
sewing start.
The factory-configured thread trimming speed (No. 49 :
210sti/min, No. 50 : 180sti/min) is lowered.
Stop the motor, fully push the thread trimming solenoid
by hand when the needle reaches the lowest point,
trim the thread while turning the hand wheel slowly,
and stop the hand wheel when the thread take-up lever
comes to the upper dead point.
If the length of the needle thread passing through the needle
at this moment is 10 mm or more shorter than that of the
pedal operation, hasten the timing of thread trimming or de-
crease the 1st thread tension because this is a midway cut.
Re-sharpen the blade of the knife in accordance.
Remove the scratches or burrs, or replace the defec-
tive component.
Change the needle.
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