JUKI lbh-1790 series Engineer's Manual page 29

Adjustment Procedures
1. Put the sewing machine in the bobbin thread trimming
adjustment mode with level 2
"1) Bobbin thread trimmer adjustment mode".
2. Put the position to thread trimming position (state in the figure
on the left side) with ITEM SELECTION key !0
Remove setscrews 1 and 2, and replace bobbin thread
trimmer 3.
(Caution) After replacing the bobbin thread trimmer 3, check
the motion with "1) Bobbin thread trimmer
adjustment mode".
1. Start up 1) Bobbin thread trimmer adjustment mode.
2. Assembling parts
(1) Making the center of the long hole of bobbin thread trimmer
working link 1 as the reference, adjust thread holding
position and open amount at the start of opening position
and, fix them.
3. Bobbin thread trimmer motion at the start of opening
(1) After start of sewing,
start distance) feed moves and
release amount at sewing start) trimmer opens.
After "Open amount at start of opening", the trimmer
gradually opens and it opens up to the release position of
K52 (Bobbin thread trimmer adjustment mode).
4. Adjustment with the operation panel
(1) Open timing and open amount can be adjusted using the
operation panel.
™ Thread at the sewing start is not interlocked or when
bobbin thread at the sewing start protrudes upward :
.... Make the bobbin thread holding section longer.
+, K21 –
™ Seams at the sewing start are gathered cramped or when
seams at the sewing start look stitch like skipping :
.... Make the bobbin thread holding shorter.
K21 +
(Caution) Change the set value little by little because of
delicate adjustment.
K52 of memory switch. Refer to
U24 (Bobbin thread trimmer motion
K21 (Bobbin thread trimer
24
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Results of Improper Adjustment
.
™ When bobbin thread is not held
at the start of sewing, it does not
interlace with needle thread and
seams may not be formed.
™ When bobbin thread holding
section is excessively long,
seams are gathered and may
look like stitch skipping.
™ When bobbin thread holding
section is excessively short,
bobbin thread at the sewing start
may be drawn out to the upside.
U24
U24 –,
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