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7. TROUBLES AND CORRECTIVE MEASURES
(1) With regard to mechanical components
1. Stitch skipping of 1 to
several stitches
occurs at the start of
sewing.
1-1) Needle thread remaining on
the needle tip after thread
trimming is too short.
1-2) Needle used is improper.
1-3) Needle thread is not caught
at the blade point of hook.
(Stitch skipping)
1)-A Needle thread path is
abnormal and needle
thread resistance at the
time of thread trimming is
strong.
1)-B Tension of thread tension
No. 1 is too high.
1)-C Rising amount of tension
disk No. 2 at the time of
thread trimming is small.
1)-D Thread trimming timing is
too early.
1)-E receding amount of
moving knife is
insufficient and needle
thread is not caught in the
thread-draw of knife unit.
1)-F Counter knife is
excessively near to
needle.
Blade tip is too sharp.
1)-G There are scratches on
knife thread guide,
moving knife, hook, and
thread-draw.
1)-H Stroke or tension of
thread take-up spring is
too large or too high.
2)-A Thread is not held and apt
to slip off since needle
hole of material does not
recover.
3)-A Timing between hook and
needle is improper.
3)-B Clearance between hook
and needle when needle
thread is caught is too
large.
3)-C Stroke or tension of
thread take-up spring is
too large or too high.
3)-D Worn-out of blade point of
hook.
3)-E Installation of needle is
improper.
3)-F Position where needle
thread is caught is
improper.
3)-G Pressure of presser foot
is too low and cloth flops.
Check the inside of needle thread paths
such as thread tangling or orientation of
thread guide bar, position (height) and
orientation (twist) of thread stand, mistake
of threading at each section, etc.
Decrease tension of thread tension No. 1
within the range where rough motion of
thread does not occur between thread
tensions No. 1 and No. 2.
Correct the rising amount of the disk
according to 4-(9). In addition, when the
disk is obliquely rising, turn 180fl the
thread tension No. 2 spring or correct the
inclination of the spring.
Correct the thread trimmer cam timing
according to 4-(6).
Correct the receding amount of moving
knife according to 4-(4).
Check and adjust the position, shape,
etc. of counter knife according to 4-(7).
Check the hook (especially, blade point
and blade), edge of knife thread guide,
moving knife (especially, thread catching
section), and scratch of thread draw-out.
If there is a scratch, polish it with buff.
When the scratch is large, replace the
part.
Adjust the stroke or the tension to a
proper one.
Aim of the machine is as follows.
Stroke : 8 mm
Tension : 0.2N
Use a needle which is as thin as
possible to adjust it to cloth or thread
count.
Correct the hook timing (aim of return
amount : 1.8 mm) according to the 4-(2).
(Use the gauge supplied as accessories.)
Correct the clearance to 0 to 0.06 mm.
Adjust the stroke to a proper one (8 mm)
or the tension to a proper one (0.2N).
Correct the blade point or replace the
hook.
Adjust the inclination of needle. (Replace
the needle when it is bent.)
Adjust the height of the needle. (Refer to
4.- (1).)
Check whether the needle is fully
inserted.
Adjust the pressure of the presser foot
according to the Instruction Manual.
Cause (1)
Troubles
Cause (2) Corrective measures
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