JUKI MF-7900 Series Engineer's Manual page 53

Adjustment procedures
1. Changing the stitch length
(1) When making the stitch length more than 3.6 mm, loosen set-
screw ❷ of the feed adjustment stopper pin, turn feed adjust
knob ❶ clockwise, and adjust the stitch length. By turning feed
adjust knob ❶ , pin ❸ is pushed out. Fix pin ❸ with setscrew
❷ 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 lock nut ❹ and raise lever ❺ to increase
the differential feed ratio (shrinkage in stitched material cloth).
When the lever is lowered, the differential feed ratio becomes
small (elongation in stitched material cloth).
Fine adjustment of the differential feed ratio can be performed
with micro-adjust knob ❻ .
(2) When setting the differential feed ratio to 1 : 0.6 to 1 : 1.1 ;
Remove setscrew ❼ in differential feed link ❽ .
Tighten differential feed link ❽ into screw hole C with setscrew
❼ which has been removed.
(3) The differential feed ratio can be changed from A to B by
changing the position of differential feed link ❽ to screw hole
C with setscrew ❼ .
(Caution) For some stitch lengths and differential feed ratios,
improper adjustments may give rise to breakage as a
result of contact between feed dogs or between feed
dog and throat plate.
Results of Improper adjustment
◦ 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.
◦ When using the machine with
the stitch length of more than 2.5
mm and the maximum differen-
tial 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 differen-
tial feed dog.
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