JUKI MF-7800D Series, Engineer'S Manual

Page: 109 / 165

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Speed of the lower thread trimmer device can be changed with speed
controllers and of air cylinder .
(1) When you desire to change the protruding speed of lower knife,
loosen the nut of speed controller , and turn the adjustment screw.
When you desire to change the returning speed of lower knife, loosen
the nut of speed controller , and turn the adjustment screw.
(2) After the adjustment, tighten the nuts of speed controllers and
.
1. Adjusting the disk-rise
(1) Loosen setscrew in adjustment cam , turn adjustment cam
and disk-rise plate moves up or down.
(2) Adjust the clearance between the click section of disk-rise plate
and thread tension disk to 0 to –0.5mm (Click section
enters thread tension disk .) and tighten setscrew .
(3) If the click section of disk-rise plate comes in contact with
thread tension disk , sewing trouble will be caused. So, be careful.
2. Adjusting the thread release hook
(1) Loosen setscrew adjust the dimension from the top end of thread
release rod to the top end of thread guide to 33 to 36 mm, and
tighten setscrew .
(2) Loosen setscrew , move the position of thread release hook
up or down, and the thread remaining length at the start of sewing
can be adjusted.
o When the protruding speed of
lower knife is slow, thread trim-
ming failure will be caused.
o When the returning speed of
lower knife is fast, lower thread
clamp failure or uneven needle
thread remaining length will be
caused.
o When the position of thread re-
lease hook is raised, the
thread remaining length at the
start of sewing is decreased and
when it is lowered, the thread re-
maining length at the start of sew-
ing is increased.
o When the thread remaining
length at the start of sewing is
short, stitch skipping or slip-off of
thread from needle eyelet at the
start of sewing is apt to occur.
Adjustment Procedure
Results of Improper Adjustment
UT25