Table of Contents
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No
Symptom
Upper thread
4
does not sink.
Lower thread
5
does not sink.
Tension of fixed blade
Edge of movable and
fixed blades
6
Trimming errors
Direction of needle
Check the crossing of
trimmer cam notch
mark and blade
Upper thread
is pulled out
7
when sewing
Check the Up-stop
commences.
position of needle
Checkpoints
Too tight upper thread tension.
Too loose lower thread tension.
Too weak upper thread tension.
Too strong lower thread tension.
Tension not aligned between
movable and fixed blades.
Abrasion in blade groove of
movable and fixed blades.
Wrong needle insertion.
Insufficient crossing quantity of
movable and fixed blade.
Too strong upper thread tension.
Too thick a needle for thread.
Take-up lever pulls out the upper
thread because the needle up and
down position is too high.
Root cause
Reduce tension of upper thread.
Increase tension of lower thread.
Increase upper thread tension.
Decrease tension of lower thread.
Adjust tension of movable and fixed
blade.
Replace movable and fixed blades.
Reinsert the needle correctly.
Adjust the strokes of movable and
fixed blades.
Adjust tension of upper thread.
Check thickness of needle.
Adjust the up-stop position of
needle.
Corrective action
43
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