JUKI LK-1900AN Engineer's Manual page 61

Adjustment procedures
1. Start the test mode CP-7.
2. Tread on the pedal for needle thread clamp 3 origin retrieval.
3. Press the key twice and set the needle thread clamp
support plate complete 4 in the needle thread clamp position.
4. Confirm that the clearance A becomes 0 between the needle
thread clamp 3 and the needle thread clamp support plate
complete 4 when the "−" key is pressed 3 to 4 times (for 3 to
4 pulses), and that both the needle thread clamp 3 and the
needle thread clamp support plate complete 4 move together
when the "−" key is pressed again.
5. If the clearance A becomes 0 with 5 or more pulses, loosen the
setscrew 1 and fix the sensor mounting plate 2 after moving
it in the direction B.
6. If the clearance A becomes 0 with less than 3 pulses, loosen
the setscrew 1 and fix the sensor mounting plate 2 after mov-
ing it in the direction C.
7. After the sensor mounting plate 2 has been fixed, check the
above mentioned steps 2. to 4.
8. Using 3 to 4 pulses, repeat the steps 2. to 6. above until the
clearance A becomes 0.
9. Tread on the pedal for needle thread clamp 3 origin retrieval
and define the most advanced position by pressing the
key once.
10. Confirm that the distances between the needle thread clamp
support plate complete 4 and the needle 5 are kept at 3 to 4
mm and 1.7 to 2.3 mm, respectively.
11. If the distance is found to be inadequate, adjust the position
toward the needle 5 according to "(36) Needle thread clamp
device connection/disconnection." Since then, make the above-
mentioned sensor adjustments again.
Results of Improper adjustment
If there are too many pulses
o
used until the clearance A be-
comes 0, this can be a cause of
unthreading at the beginning of
sewing.
If the number of pulses is too
o
small until the clearance A be-
comes 0, the resistance toward
the needle thread becomes
large and this can be a cause of
thread breakage at the begin-
ning of sewing.
If the distance is improper be-
o
tween the needle thread clamp
support plate complete 4 and
the needle 5 , this will give rise
to interference between the
needle thread clamp 3 and the
needle 5 .
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