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Cause (1)
Troubles
Cause (2)
Corrective measures
From the previous page
5. Needle thread is not
cut. (Bobbin thread
is cut.)
5-1) Stitch skipping at the last sti
5-2) Slackness of needle thread
during thread trimming motion is
large and needle thread cannot be
caught when moving knife returns.
5-3) When moving knife draws out
thread during thread trimming
motion, two pieces of needle
thread are simultaneously caught
at the concave section of top end
of moving knife.
5-4) A part of cutting blade section
of knife is dull.
1)-D There is a scratch on
knife thread guide, moving
knife, hook, or thread draw-
out, and trimming on the way
occurs.
1)-E Tension releasing timing
is too late and trimming on the
way occurs.
1)-F Lateral position of knife
unit is improper and thread
draw-out with moving knife
cannot be performed. (3 pcs.
trimming)
1)-G Hook timing is too early
and thread draw-out with
moving knife cannot be
performed.
1)-H Tension release timing is
too early and thread draw-out
with moving knife cannot be
performed.
1)-I Thread trimming timing is
too late and thread draw-out
cannot be performed.
1)-A Installation of needle is
wrong.
1)-B Stroke of thread take-up
spring is too large.
1)-C Hook adjustment is
wrong.
2)-A Tension release timing is
too early.
2)-B Hook timing is too late.
2)-C Thread trimming timing is
too early.
3)-A Lateral position of knife
unit is improper.
4)-A Cutting blade sections of
moving knife and counter knife
are not completely fit at the
time of thread trimming.
(Installing angle, position and
inclination of blade plane of
counter knife are not fit for the
blade section of moving knife.)
Correct the scratch with buff or replace the
part.
Check the set value of LS (Output start
angle of L output of G mode) according
to 5. Reference.
When waste thread of approximately 40
mm is fallen under throat plate, it is 3
pcs. trimming. Correct the position of
knife unit according to (5).
* When adjusting the lateral position of
knife unit, the receding amount of
moving knife varies and re-adjustment is
necessary.
(Refer to 4. - (2) Hook timing.) Correct
the hook timing (aim of return amount :
1.8 mm).
(Use the gauge supplied as
accessories.)
Refer to 5. SETTING OF SC-380. Check
the set value of LS (Output start angle of
L output of G mode).
Correct the thread trimmer cam timing
according to 4-(6).
Correctly install the needle according to
the Instruction Manual. In addition, check
the bend of needle.
Decrease the stroke of thread take-up
spring.
Check stitch skipping with sewing at low
speed and try again the hook adjusting.
(Make the hook timing somewhat
earlier.)
Check the set value of LS (Output start
angle of L output of G mode) according
to 5.
Correct the hook timing (aim of return
amount : 1.8 mm) according to the 4-(2).
(Use the gauge supplied as accessories.)
Correct the thread trimmer cam timing
according to 4-(6).
Adjust the lateral position of knife unit
according to 4-(5).
* When adjusting the lateral position of
knife unit, the receding amount of
moving knife varies and re-adjustment is
necessary.
Remove the throat plate, and move the
moving knife by hand. It is good that 3
pcs. of cotton thread #50 are evenly cut
when 3 pcs. of the thread are cut. If not,
adjust the position and sharpening
procedure of counter knife according to
4-(7) and 6-(1).
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