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Bad
Cause
condition
Too short bobbin thread by
bobbin spinning after
trimming
Bobbin thread tension is too
3.
tight
Skip stitch
Thread tail from needle is
happens at
very short after trimming
start sewing
Pre-tension is too loose
4.
Trimmer timing is delayed
Thread tail
from needle is
Upper thread tension release
too long after
timing is too fast
trimming
Tread guide is in wrong
position
Trimmer function is canceled
Fixed knife is dull
Movable Knife is in wrong
5.
position
Trimming is
Skip stitching happens at
not functioned
trimming
Trimmer timing is wrong
Needle and shuttle hook
clearance is too big
Needle and shuttle hook
timing is not correct
6.
Needle is bent
Skip stitching
Needle is bent by driver
often happens
Needle is in wrong position
Presser foot position is not
correct
From the library of: Superior Sewing Machine & Supply LLC
Remedy
Use non racing spring with bobbin
Loosen bobbin thread tension spring
Decrease pre-tension
Adjust trimmer cam position
Adjust synchronizer position
Make thread take up swing stroke smaller
Advance thread tension release timing
Adjust thread guide position properly
Make pre-tension tighter
Adjust trimmer cam position
Adjust synchronizer position
Delay tension release timing
Adjust thread guide position properly
Resume trimmer function
Change it new knife
Adjust movable knife position properly
Fix skip stitching
Adjust trimmer cam position
Adjust synchronizer position
Adjust needle and shuttle hook timing
properly
Adjust needle and shuttle hook timing
properly
Change it new needle
Adjust needle and diver clearance
properly
Amend needle position
Adjust presser foot position properly
28
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Ref. page &
item
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6-3
7-16
7-10
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7-13
Control unit
7-5
7-14
7-10
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Control unit
7-5
Control unit
7-11
7-11
7-6
7-10
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7-2
7-2
—
7-4
7-2
7-6
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