JUKI lbh-1790 series Engineer's Manual page 25

Adjustment Procedures
1. Loosen setscrews 2 in draw-in link B 1 and move needle
thread draw-in arm 3 to adjust needle thread draw-in amount
A (position of needle thread draw-in lever 4) at the time of
needle thread trimming.
2. Reference of adjustment is to adjust A to "0" when draw-in link
B 1 is assembled in the center of long hole and loosen
setscrews 2 in the direction of increasing the needle thread
draw-in amount.
Adjustment Procedures
1. Press MODE key 4
enter memory switch level 2 of the adjustment mode.
with ITEM SELECTION key !0
2. Select K52
READY key 2
to enter bobbin thread trimmer adjustment
mode.
3. Every time ITEM SELECTION key !0
four positions as shown in the figure are repeatedly moved
and can be changed over in order.
Thread release position / Waiting position / Thread trimming
position / Thread holding position
4. To change the set value, move the state to the position you
desire to set, and set the value with DATA CHANGE key !1
.
5. Adjust the thread release position so that the distance from
the top end of lower knife to the holding spring is 3 to 4 mm.
6. Adjust the thread trimming position so that the lower knife and
the holding spring are almost flush with each other.
7. When READY key 2
performed from any position and the position moves to the
origin position.
8. When STOP button is pressed when the position is moved to
the thread holding position, the position moves from the thread
holding position to the open amount at the start of opening
(value set with K21 , initial value : 8). Then it can be checked
that how much the bobbin thread trimmer opens when it starts
opening at the start of sewing. Every time STOP button is
pressed, the move between thread holding position and open
amount at start of opening repeats. For the setting procedure,
refer to "4) Open timing and open amount.
9. When RESET key 3
values are memorized in EEPROM of the machine head and
the bobbin thread trimmer adjustment mode is completed.
for approximately three seconds to
is pressed, the
is pressed, origin retrieval can be
is pressed, the respective moving set
20
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Results of Improper Adjustment
™ When needle thread draw-in
a m o u n t i s e x c e s s i v e l y
increased, or needle thread
draw-in arm 3 is excessively
tilted, malfunction occurs.
Results of Improper Adjustment
When the set value at each position is
changed, it becomes as follows.
, and press ™ Thread release position
(Initial value : -22 pulses)
When the value is decreased,
opening amount is increased.
When the value is increased, it is
decreased. When the trimmer is
opened, be careful that the trimmer
is not caught in the needle hole.
When the opening amount is
excessively small, bobbin thread
may not be trimmed.
™ Waiting position
(Initial value : "0" pulse)
Waiting position of the trimmer
before thread trimming can be
adjusted. When the set value is
changed, the trimmer may interfere
with needle.
™ Thread trimming position
(Initial value : 50 pulses)
When the value is increased,
overlapping of upper/lower knives
of trimmer is increased and when it
is decreased, the overlapping is
decreased. When the value is
excessively increased, thread
holding after trimming bobbin
thread cannot be prerformed.
When the value is excessively
decreased, the trimmer cannot be
fully closed and thread is not
trimmed.
™ Thread holding position
(Initial value : "0" pulse)
Thread holding position at the start
of sewing can be adjusted.
When the set value is changed, the
trimmer may interfere with needle.
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