JUKI MF-7900 Series Engineer's Manual page 105

Adjustment procedures
1. Adjusting the engagement of knives
(1) Adjust so that the engagement of fixed knife ❶ with moving
knife ❷ is 0.5 mm.
(2) When adjusting the engagement, loosen setscrews ❹ and
move knife holder ❺ up or down to adjust.
2. Adjusting the pressure of clamp spring
(1) Top covering thread is held with clamp spring ❸ after thread
trimming.
(2) Holding pressure can be adjusted by loosening nut ❻ and turn-
ing screw ❼ .
(3) Holding pressure is increased when tightening screw ❼ and it
is decreased when loosening screw ❼ .
(4) After the adjustment, tighten nut ❻ .
(5) Make the holding pressure as low as possible within the range
of holding the top covering thread.
3. Adjusting the position of the blade point of moving knife
(1) Bring the needle bar to its highest position.
(2) When hinge screw ❽ is lowered, moving knife ❷ lowers togeth-
er.
(3) Adjust so that the hook of moving knife ❷ enters the recess in
the top face of spreader ❾ to be brought to the position where
the moving knife ❷ catches the top covering thread when mov-
ing knife ❷ is brought to the lowermost position. Then, tighten
screws  ,  and  .
Adjust the moving knife ❷ vertically so that a clearance of 0.5
mm is provided between the recess section of spreader ❾ and
the moving knife ❷ , and laterally so that the moving knife ❷ is
brought to the center of the width of recess in spreader ❾ , as
illustrated in Figure A.
(4) Screws  are for adjusting vertical position of the knife, screws
 for adjusting lateral position of the knife, and screws  for
adjusting angle of the knife.
(Caution) Make sure that the moving knife does not interfere
with other components such as presser, needle,
spreader ❾ , etc. within the working range of moving
knife ❷ .
4. Adjusting the speed of moving knife
Stroke of air cylinder  is 20 mm.
Speed of the moving knife ❷ can be changed with speed controllers
 and  .
(1) When you desire to change the protruding speed of moving
knife ❷ , loosen the nut of speed controller  and turn the ad-
justment screw.
When you desire to change the returning speed of moving knife
❷ , loosen the nut of speed controller  and turn the adjust-
ment screw.
(2) After the adjustment, tighten the nuts of speed controllers 
and  .
1. When the protruding speed of moving knife ❷ is
(Caution)
slow, thread trimming failure will be caused.
2. When the returning speed of moving knife ❷ is
fast, needle thread clamp failure will be caused.
Results of Improper adjustment
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