JUKI MF-7800D Series, Engineer'S Manual

Page: 43 / 165

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1. When making the stitch length more than 3.6 mm, loosen setscrew
of the feed adjustment stopper pin, turn feed adjust knob
clockwise, and adjust the stitch length. By turning feed adjust knob
, pin is pushed out. Fix pin with setscrew in the feed
adjustment stopper pin after adjusting the stitch length.
Maximum stitch length is 4.5 mm.
2. Changing the differential feed ratio
(1) Loosen differential feed lock nut and raise lever to increase
the different feed ratio, and the finished material gathers. Lower lever
to decrease the differential feed ratio, and the finished material
stretches. Fine adjustment of the differential feed ratio can be
performed with micro-adjust knob .
(2) <When setting the differential feed ratio to 1 : 0.6 to 1 : 1.1>
Remove setscrew in differential feed link .
Tighten differential feed link into screw hole with setscrew
which has been removed. (Differential feed ratio becomes
A
to
B
.)
(Caution) When the adjustment is performed, both feed dogs or
feed dog and throat plate may come in contact with each
other and be broken due to the relation between the
stitch length and the differential feed ratio. So, be careful.
o When the stitch length is set to
more than 3.6 mm, the contact
of main feed dog, differential feed
dog and throat plate occurs due
to the adjustment in case of the
standard position of the feed dog.
Additionally machine the feed
dog to satisfy the need.
o When using the machine with the
stitch length of more than 2.5 mm
and the maximum differential
feed ratio, turn the machine by
hand and check whether there is
any contact with feed dog and
throat plate.
In addition, when more gathering
is necessary, grind the differential
feed dog.
Adjustment Procedure
Results of Improper Adjustment
A B
Differential feed ratio :
1 : 0.9 to 1 : 1.8
1 : 1.8
1 : 1
1 : 0.9
Differential feed ratio :
1 : 0.6 to 1 : 1.1
1 : 1.1
1 : 0.6
1 : 0.9