JUKI MF-7900 Series Engineer's Manual page 63

Adjustment procedures
When performing balloon stitch, carry out the
adjustment referring to the adjustment values de-
scribed below.
(Caution) Balloon stitches may not be formed
smoothly according to the type of
thread and fabric.
[2-needle balloon stitch without top covering]
① Feed timing
Feed driving eccentric cam : Retard the timing
Feed rocking eccentric cam : Retard the timing
* Refer to "4.-(14)-3. Adjusting the feed locus".
② Looper thread cam timing
Looper thread comes off the looper thread cam ❷ in the middle
between the lower end face and upper end face of the looper ❹ .
[Adjusting the looper thread cam]
Adjust so that the looper thread comes off the looper thread cam ❷
when the top end of the lowering left needle ❸ comes to the middle
between the lower end face and upper end face of the looper ❹
when the lowering left needle. Then, fix the looper thread cam with
setscrews ❶ .
③ Hauling amount of the looper thread cam
The position 6 mm lower than the standard position
(Standard: Aligns with the upper marker line)
④ Matchstick height
Matchstick height
Right needle 17 mm
Left needle 29 mm
⑤ Needle bar thread take-up thread receiver
The needle bar thread take-up thread receiver ❺ aligns with the top
end of the needle bar thread take-up when the needle bar is in its
lower dead point.
⑥ D claw (standard: B claw)
⑦ Differential feed ratio
Slightly stretch the material.
Results of Improper adjustment
– 49 –