JUKI MF-7900 Series Engineer's Manual page 103

Adjustment procedures
1. Adjusting the thread trimmer air cylinder
(1) Stroke of air cylinder ❸ is 18 mm.
When adjusting the stroke, loosen setscrew ❷ of collar ❶ and
move collar ❶ to the right or left to adjust.
2. Adjusting the thread trimmer sensor
The safety switch is installed so that the sewing machine does not
start unless the looper thread trimmer device returns to its home
position.
(1) Loosen setscrews ❹ .
(2) Adjust switch plate ❺ so that LED of thread trimmer sensor
❻ lights up in the state that the thread trimmer device is fully
returned to its home position.
(3) Tighten setscrews ❹ .
(Caution) Perform the work with the needle bar at the highest
position when actuating the thread trimmer mecha-
nism by hand.
3. Adjusting the speed of looper thread trimmer
Speed of the looper thread trimmer device can be changed with
speed controllers ❼ and ❽ of air cylinder ❸ .
(1) When you desire to change the protruding speed of lower knife,
loosen the nut of speed controller ❼ , and turn the adjustment
screw.
When you desire to change the returning speed of lower knife,
loosen the nut of speed controller ❽ , and turn the adjustment
screw.
(2) After the adjustment, tighten the nuts of speed controllers ❼
and ❽ .
(Caution) 1. When the protruding speed of lower knife is
slow, thread trimming failure will be caused.
2. When the returning speed of lower knife is fast,
lower thread clamp failure or uneven needle
thread remaining length will be caused.
Results of Improper adjustment
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