JUKI MF-7900 Series User manual

INSTRUCTION MANUAL
M)'/UT59

i
CONTENTS
I. SPECIFICATIONS.............................................................................................................1
II. AT THE BEGINNING........................................................................................................1
III. INSTALLING THE ACCESSORIES................................................................................2
1. Installing the air regulator ................................................................................................................... 2
2. Installing the manifold ......................................................................................................................... 2
3. Connecting the cords .......................................................................................................................... 3
4. Setting procedure of the machine head............................................................................................. 4
IV. AIR PIPING DRAWING...................................................................................................5
1. Piping of the thread trimmer device................................................................................................... 5
2. Adjusting the air regulator................................................................................................................... 5
V. THREADING THE MACHINE HEAD...............................................................................6
VI. ADJUSTING THE LOOPER THREAD TRIMMER MECHANISM ..................................7
1. Initial position of the looper thread trimmer mechanism................................................................. 7
VII. INSTALLING THE SS LEVER UNIT .............................................................................8
1. Installing the SS lever unit .................................................................................................................. 8
2. Adjusting the SS lever unit.................................................................................................................. 8
VIII. DRAWING OF THE TABLE..........................................................................................9
IX. SETTING THE UPPER STOP POSITION OF THE NEEDLE BAR .............................10
X. SETTING THE RAVELING PREVENTION PARAMETER ............................................12

– 1 –
I. SPECIFICATIONS
Model name High-speed, cylinder-bed coverstitch machine
Model MF-7900 series
Stitch type ISO standard 406, 407, 602, and 605
Example of application For preventing thread from raveling at the end of hemming or other processes
Sewing speed Max. 6,000 sti/min (at the time of intermittent operation) Direct-drive type
Speed of stitch at the delivery: 4,500 sti/min (at the time of intermittent operation)
Needle gauge 3-needle ..... 5.6 mm and 6.4 mm
2-needle ..... 4.0 mm and 4.8 mm
Differential feed ratio 1 : 0.9 to 1 : 1.4 (stitch length : less than 2.5 mm) * Only for H23
(1 : 0.6 to 1 :1 .1, when the differential link hinge screw is changed)
Micro-differential feed adjustment mechanism is provided. (Micro-adjustment)
Stitch length 0.9 mm to 3.6 mm (can be adjusted up to 4.5 mm)
Needle UY128GAS #9S to #14S (standard #10S)
Needle bar stroke 31mm (33 mm when the eccentric pin is changed over)
Dimensions (Height) 450 x (Width) 456 x (Length) 299
Weight 45 kg (With pneumatic type thread trimmer)
Lift of presser foot 8 mm (needle gauge : 5.6 mm without top covering), and 5 mm (with top covering)
Micro-lifter mechanism is provided.
Feed adjustment
method
Main feed............... dial type stitch pitch adjustment method
Differential feed ..... lever adjustment method (micro-adjustment mechanism is provided.)
Looper mechanism Spherical rod drive method
Lubricating system Forced lubrication method by gear pump
Lubricating oil JUKI GENUINE OIL 18
Oil reservoir capacity Oil gauge lower line : 600 cc to upper line : 900 cc
Installation Table-mount type, Semi-submerged type
Noise - Equivalent continuous emission sound pressure level (LpA) at the workstation:
A-weighted value of 79.5 dB; (Includes KpA = 2.5 dB); according to ISO 10821- C.6.2 -ISO 11204 GR2 at 4,500
sti/min.
Remove xed band ❶for transportation before setting
up the sewing machine.
II. AT THE BEGINNING
❶

– 2 –
❶
❷
III. INSTALLING THE ACCESSORIES
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the
following work after turning the power off and ascertaining that the motor is at rest.
1) Install air regulator asm. ❶under the table with
wood screws ❷.
1. Installing the air regulator
Install manifold asm. ❶on the table with wood screw
❷.
2. Installing the manifold
❷
❶

– 3 –
2) Loosen screw Bin cover ❷with a screwdriver to
open the cover.
3) Connect 14P code ❸coming
from the machine head to con-
nector ❻(CN36).
4) Insert 3P cord ❾coming from
the machine head into connec-
tor 󱢳(CN42).
5) Insert presser foot lifter cord 2P
❹into connector ❼(CN37).
6) Connect connector ❺coming
from the motor to connector ❽
(CN30) on the circuit board.
7) Insert pedal sensor cable 󱢴into connector 󱢵(CN34).
8) Insert motor fan cord 󱢶into connector 󱢷.
9) Insert 8P cord 󱢸to connector 󱢹(CN56).
[Connecting the connector for the operation panel]
Be sure to turn OFF the power before con-
necting the connector.
Be sure to securely insert the respective connectors after checking the inserting directions since all connec-
tors have the inserting directions. (When using a type with lock, insert the connectors until they go to the
lock.) The sewing machine is not actuated unless the connectors are inserted properly. In addition, not only
the problem of error warning or the like occurs, but also the sewing machine and the control box are damaged.
The connector for the operation panel is provided.
Paying attention to the orientation of the connector 󱢸,
connect it to connector (CN38) 󱢹located on the circuit
board. After the insertion, securely lock the connectors
to prevent them from coming off easily.
󱢸
󱢹
❷
B
3. Connecting the cords
1) Pass cords ❶and 󱢸of the thread-trimming sole-
noid, reverse feed stitching, motor signal etc. and
the motor cord through the hole Ain the table to
route them to the underside of the table.
❶
󱢸
A
❼
❹
❺
❽
❸
❻
❾
󱢵
󱢳
󱢴
󱢶
󱢷
󱢸
󱢹

– 4 –
❹
❸❷❶
Type of machine head Model name
F799 MF-7900/UT59
For the operation panel other than CP-18, refer to the Instruction Manual for the operation panel to be used
for the setting procedure of the machine head.
1) Call function setting No. 95.
2) The type of machine head can be se-
lected by pressing switch
❸
(
switch
❹
).
* Refer to the "MACHINE HEAD LIST"
on the separate sheet or the Instruc-
tion Manual for the machine head of
your sewing machine for the type of
the machine head.
3) After selecting the type of machine
head, by pressing switch ❶(
switch ❷), the step proceeds to 96
or 94, and the display automatically
changes to the contents of the setting
corresponding with the type of ma-
chine head.
❹
❸❷❶
❹
❸❷❶
4. Setting procedure of the machine head

– 5 –
IV. AIR PIPING DRAWING
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the
following work after turning the power off and ascertaining that the motor is at rest. In addition, cut the air
supply from air compressor.
1. Piping of the thread trimmer device
❶
❷
❸A
󰽈
Air hose
1) Insert the air hose to air regulator ❶.
2) Use the air pressure at 0.4 to 0.5 MPa (4 to 5 kgf/
cm2).
3) Draw up regulator knob ❷, turn knob ❷and ad-
just the pointer to 0.4 to 0.5 MPa to adjust the air
pressure.
4) After the adjustment, press downward regulator
knob ❷.
5) When drainage is collected at section Aof regula-
tor ❶during using, press drain cock ❸to dis-
charge the drainage.
2. Adjusting the air regulator

– 6 –
* For the adjustment procedure other than the above, refer to the Instruction Manual for MF-7900.
❶❷
Thread the machine head according to the following threading illustrations.
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the
following work after turning the power off and ascertaining that the motor is at rest. If threading is wrong,
stitch skipping, thread breakage, needle breakage or irregular stitches will be caused. So, be careful.
V. THREADING THE MACHINE HEAD
When the small thread tension in the face plate is used for the machine with the thread trimmer device,
the length of remaining needle thread after thread trimming becomes short and slip-off of thread at the
start of sewing may occur.
❶
❷

– 7 –
VI. ADJUSTING THE LOOPER THREAD TRIMMER MECHANISM
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the
following work after turning the power off and ascertaining that the motor is at rest. In addition, cut the air
supply from air compressor.
When lower knife ❹is located at its leftmost position,
the top end of the lower knife ❹has to be spaced 24 ±
0.5 mm from the center of needle bar.
1. Initial position of the looper
thread trimmer mechanism
Center of needle
bar
24 ± 0.5 mm
❹
Perform the work with the needle bar at the
highest position when actuating the thread
trimmer mechanism by hand.

– 8 –
VII. INSTALLING THE SS LEVER UNIT
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the
following work after turning the power off and ascertaining that the motor is at rest.
1. Installing the SS lever unit
❷
❸
❹
❶
1) Install SS lever unit ❹using SS lever unit setscrews 1 ❶, SS lever unit setscrews 2 ❷and SS lever unit
washers ❸supplied as accessories.
* Temporarily tighten SS lever unit setscrews 2 ❷at the center position of the slot and securely tight-
en the setscrews after performing the trial sewing and adjusting the stitch pitch of the short stitch.
 Inaddition,installtheSScoverafternishingtheworkofsecurelytighteningofthesetscrews.
Refer to "2. Adjusting the SS lever unit" p.8 for how to adjust and install the SS lever unit.
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the
following work after turning the power off and ascertaining that the motor is at rest. In addition, cut the air
supply from air compressor.
2. Adjusting the SS lever unit
❷
❸
❹
❺
❶
A
B
1) Loosen setscrews ❷in SS lever ❶, move the lever up and down to adjust the position, and the stitch pitch
of the short stitch can be adjusted.
* Commendable stitch pitch is 1.4 mm. (The center position of the slot of SS lever is the standard.)
Turn SS lever ❶in the direction of Ato increase the stitch pitch, and turn it in the direction of Bto decrease
the stitch pitch.
2) When the adjustment is completed, install SS cover
❹
using setscrew
❸
supplied as accessories. Setscrew
❺
has to
be tightened together with the pitch scale plate.

– 9 –
VIII. DRAWING OF THE TABLE
DRAWING OF TABLE (SEMI-SUBMERGED TYPE) H22/23-UT59 DIRECT-DRIVE TYPE
(Drill a hole at the
time of set-up.)
Installing position of drawer
stopper (on the reverse side)
Drilled hole 17
(Drill a hole at the time
of set-up.)
Z-Z (four locations)
4 - ø 3.4 on the bottom
surface, depth 20
2 - ø 3.4 on the bottom surface, depth 10
4 - 10.5 hole, 26 hole facing
depth 3.5

– 10 –
IX. SETTING THE UPPER STOP POSITION OF THE NEEDLE BAR
Ⓑ
❻
❺❹❸
Ⓐ
❸❻ ❺❹
❻
❺❹❸
Ⓑ
4) In this state, give the pulley of the machine head
another turn by hand to align marker line ❶on the
hand pulley with recess ❷in the frame as shown
in the gure.
The direction of rotation is clockwise. If the
pulley is turned counterclockwise, the degree
of the aforementioned angle can differ by
approximately two degrees.
1) Simultaneously pressing switch
❹and switch ❺, turn ON the
power switch.
2) is displayed ( Ⓐ) in the indica-
tor and the mode is changed over to
the adjustment mode.
3) Give the pulley of the machine head
a turn by hand. Then, the main shaft
reference signal is detected. The
degree of an angle given by the main
shaft reference signal is indicated on
display section Ⓑwith a blip.
(The value is the reference value.)
5) Press switch ❻.
(The value is the reference value.)
Take a note of the numeric value
shown on display section Ⓑsince it is
used for "X. SETTING THE RAVEL-
ING PREVENTION PARAMETER"
p.12".
❶
❷

– 11 –
When the needle
moves in the
descending
direction
6) Remaining in the needle-bar upper stop position
setting mode, turn the hand pulley of the machine
head by hand to lower the needle until the position
where its tip is aligned with the center of the looper
is reached. Keeping the needle at that position,
take a note of the numeric value shown on display
section Ⓑ. It is necessary to take a note of the
numeric value shown on display section Ⓑsince it
is used for "X. SETTING THE RAVELING PRE-
VENTION PARAMETER" p.12".
If you press switch ❻in this state, the
upper stop position of the needle bar is set
again. To prevent this, be sure to turn off the
power once without pressing any switch.
❻
❺❹❸
ⒷThe direction of rotation is clock-
wise. If the pulley is turned coun-
terclockwise, the degree of the
aforementioned angle can differ
by approximately two degrees.

– 12 –
1) Turn ON the power with switch
❼held pressed.
(The item which has been changed
during the previous work is displayed.)
* If the screen display does not change,
re-carry out operation described in
step 1).
(Caution) Be sure to re-turn ON the power
switch when one or more seconds
have passed after turning it OFF. If the
power switch is re-turned ON immedi-
ately after turning it OFF, the sewing
machine may fail to operate normally.
In such a case, be sure to turn ON the
power switch again properly.
Ⓑ
Ⓐ
Ⓒ
Ⓓ
❻❺❹❸
❶
❷❼
Ⓔ
X. SETTING THE RAVELING PREVENTION PARAMETER
2) Press switch ❸or switch ❹
to set the setting number at 128. The
current set value is shown on display
section Ⓑ.
Press switch ❺or switch ❻
to lower the left needle until its tip is
aligned with the center of the looper.
At this time, read the displayed value.
Change the value shown on display
section Ⓑto a value which is ob-
tained by subtracting the value shown
on display section Ⓑin 5) "IX. SET-
TING THE UPPER STOP POSITION
OF THE NEEDLE BAR" p.10 from
the aforementioned value.
3) After completion of the changing procedure, press switch ❸or switch ❹ to conrm the updated value.
(Caution) If the power is turned OFF before carrying out this procedure, the changed content is not updated.
When switch ❸is pressed, the display on the panel changes to the previous setting No. When
switch ❹is pressed, the display on the panel changes to the subsequent setting No. After completion
of the operation, the machine is returned to the normal sewing state by turning OFF the power and
re-turning it ON.
❻
❺❹❸
Example) The value shown on display section Ⓑin 5) "IX. SETTING THE UPPER STOP POSITION OF THE
NEEDLE BAR" p.10 is 5. The value displayed when the descending left needle tip is aligned with the cen-
ter of the looper is 90. Subtract the former value 5 from the latter value 90. (i.e., 90 - 5 = 85)
Press switch ❺or switch ❻to change the value shown on display section Ⓑto 85.