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Trouble
Cause (1)
Cause (2)
Check and corrective measures
1. Skipping of one or more
stitches occurs at the start
of sewing.
1-1) The needle thread pass-
ing through the needle
is too short after thread
trimming.
1-A) Something is wrong with the needle
threat route and the needle thread
tension is too high at thread trimming.
Check needle thread routing, thread entangled on
thread guide rod the direction, and position of thread
stand or thread entangled on it.
1-B) The tension of the 1st thread tension
disk is too high.
Turn the thread tension nut of the 1st thread tension
disk counterclockwise to decrease the tension.
1-C)
The floating amount of the 2nd thread
tension disk is insufficient at thread
trimming.
Check whether the floating amount of the 2nd thread
tension disk reads between 0.5 and 1 mm when the
hook thread presser is pushed into until the tip of the
presser reaches the bobbin.
The floating amount is adjustable by moving the ten
-
sion release wire on the underside of the bed.
Check whether the disk is horizontally loosened. If not,
turn the thread tension spring 180 degrees or correct
the spring inclination.
1-D) The timing of the tread trimming cam
is too early.
Check and correct the cam timing in accordance with
3.-(9)-3).
1-E) The needle thread is detached at
thread trimming due to wrong position
of the hook thread presser.
If there is a clearance at the tip of the hook thread
presser when the plunger is pushed by a finger to put
the thread trimming solenoid into the suction state and
the hook thread presser is pushed into until the tip of
the presser reaches the bobbin, conduct readjustment
with reference to 3.-(9) -4).
1-F) The counter knife is too close to the
needle, or the knife tip is too sharp.
Removing the throat plate, check and correct the po-
sition of the counter knife, or check for any scratch on
the moving knife (Refer to 3.-(9) -4)).
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11. Troubles and corrective measures
(1) Mechanical components
