JUKI MF-7900D/UT55, MF-7900D/UT57, MF-7900D/UT56, MF-7900/UT55, MF-7900/UT57 Instruction Manual

MF-7900(D)/UT55,56,57

INSTRUCTION MANUAL

No.01

2

70002031

Be sure to securely insert the respective connectors after checking the inserting directions since all connectors 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.

[Connecting the connector for the operation panel]

!6

!5

The connector for the operation panel is provided. Paying attention to the orientation of the connector !5, connect it to connector (CN38) !6 located on the circuit board. After the insertion, securely lock the connectors to prevent them from coming off easily.

Be sure to turn OFF the power before connecting the connector.

– 4 –

(4) Setting procedure of the machine head

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.

321

4

2) The type of machine head can be

selected by pressing

switch 4).

* Refer to the

on the separate sheet or the

LIST"

"MACHINE HEAD

switch 3 (

Instruction Manual for the machine head of your sewing machine for the type of the machine head.

321

4

Type of machine head Model name

MF-7900/UT55

F79

F79d

MF-7900/UT56

MF-7900/UT57

MF-7900D/UT55

MF-7900D/UT56

MF-7900D/UT57

3) After selecting the type of machine

head, by pressing switch

1

(

switch 2), the step proceeds to

96 or 94, and the display automatically changes to the contents of the setting corresponding with the type of machine head.

321

4

– 5 –

(5) Setting the lower stop position of the needle bar

Call function setting No. 122. Check to be sure that the lower stop position of the needle bar is as shown in not, adjust the lower stop position of the needle bar properly using function setting No. 122. (Adjustment can be made within the range of ±15°).

Fig. 1

. If

Fig. 1

321

4

– 6 –

$

. 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 (UT57)

3

4

!1

@3

2

!1

9

!0

!1

1

– 7 –

2. Piping of the thread trimmer device (UT55)

3

4

@3

!1

9

– 8 –

3. Piping drawing for air blow (UT56)

3

4

5

3

5

6

@3

4. Adjusting the air regulator

2

Air hose

1

3

@3

A

2

1

1) Insert the air hose to air regulator

1

.

2) Use the air pressure at 0.4 to 0.5 MPa (4 to 5 kgf/ cm2).

3) Draw up regulator knob

, turn knob 2 and adjust

2

the pointer to 0.4 to 0.5 MPa to adjust the air pressure.

4) After the adjustment, press downward regulator knob 2.

5) When drainage is collected at section A of regulator

during using, press drain cock

1

3

to

discharge the drainage.

– 9 –

%

. THREADING THE MACHINE HEAD

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.

Thread the machine head according to the following threading illustrations.

2

1

* For the adjustment procedure other than the above, refer to the Instruction Manual for MF-7900.

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.

1

2

– 10 –

^

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.

1. Adjusting the thread trimmer air cylinder

1) Stroke of air cylinder 3 is 18 mm.

2

1

3

18 mm

When adjusting the stroke, loosen setscrew

collar 1 and move collar adjust.

1

of

2

to the right or left to

– 11 –

4

0.5 mm

4

65.5 mm

2.5 ± 0.5 mm

!0

8

7

6

5

9

2. Adjusting the Lower knife

1) Set lower knife 4 and lower knife holder 5 with setscrews 6 at the position of the illustration.

3. Adjusting the position of clampAdjusting the position of clamp pressure adjusting spring

1) Loosen screws 9.

2) Adjust so that a clearance of 2.5 ± 0.5 mm is provided between the top end of clamp pressure adjusting spring !2 and the top end of lower knife 4 when the lower knife 4 is brought to the rightmost position.

3) After the adjustment, tighten screws 9.

4. Adjusting the knifeAdjusting the knife engagement and the knife pressure adjusting spring

1) Loosen screws 7 and 8, and adjust the position of upper knife !0 so that the engagement of the upper knife !0 with the lower knife is 0.5 mm when lower knife 4 moves to the extreme right.

2) At the same time, adjust so that a clearance of

0.5 to 1 mm is provided between knife pressure adjusting spring !1 and clamp pressure adjusting spring !2.

3) After the adjustment, tighten screws 7.

!2

4

!1

Clearance of 0.5 to 1 mm

!2

5. Adjusting the pressure of clamp spring

1) The looper thread is held by clamp pressure adjusting spring !2 after thread trimming.

2) Holding pressure of the looper thread can be adjusted by turning screw 8.

3) When screw 8 is turned clockwise, the holding pressure is increased and turned counterclockwise, the pressure is decreased.

4) Make the holding pressure as low as possible within the range of holding the looper thread.

!1

– 12 –

4

Center of needle bar

6. Initial position of the looper thread trimmer mechanism

When lower knifeknife 4 is located at its leftmost position, the top end of the lower knifeknife

0.5 mm from the center of needle bar.

has to be spaced 22 ±

4

22 ± 0.5 mm

!4

0 to 0.1 mm

!3

4

!2

0.3 to 1 mm

7. Adjusting the stopper

Check the leftmost point with the pneumatic device turned on. Adjustment should be carried out with the air pressure set at 0.5 MPa. Adjust the position of stopper

0.3 to 1 mm is provided between looper !3 and clampclamp pressure adjusting spring !2 when the counter knife is located at its leftmost position (forward end).

so that a clearance of

!4

8. Adjusting the height of the lower knife

When the needle is positioned at its upper dead point, the clearance of 0 to 0.1 mm has to be provided between the under surface of lower knife surface of looper !3.

Perform the work with the needle bar at the highest position when actuating the thread trimmer mechanism by hand.

and the top

4

!3

9. Adjusting the lower knife holder guide

When the lower knife moves from right to left, the lower knife guide holder should lightly comes in contact with the guide.

Light contact

– 13 –

Blade point of lower knife is in the center of thickness of looper.

!3

9 mm

4

!5

5

10. Adjusting the longitudinal position of the blade point of lower knife

1) Bring the needle bar to its highest position.

2) Adjust so that the blade point of lower knife 4 is in the center of the thickness of looper !3 when the clearance between the right-hand edge of looper

and the blade point of lower knife 4 is 9 mm.

!3

3) Loosen nut !5, move lower knife holder 5 to and fro, and adjust the position of the blade point of lower knife 4.

4) After the adjustment, tighten nut !5.

Perform the work with the needle bar at the highest position when actuating the thread trimmer mechanism by hand.

!7

!6

!8

@2

3

@3

11. 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 !6.

2) Adjust switch plate !7 so that LED of thread trimmer sensor !8 lights up in the state that the thread trimmer device is fully returned to its home position.

3) Tighten setscrews !6.

Perform the work with the needle bar at the highest position when actuating the thread trimmer mechanism by hand.

12. Adjusting the speed of looper thread trimmer

Speed of the looper thread trimmer device can be changed with speed controllers @2 and @3 of air cylinder

.

3

1) When you desire to change the protruding speed of lower knife, loosen the nut of speed controller @2, and turn the adjustment screw.

When you desire to change the returning speed of

lower knife, loosen the nut of speed controller @3, and turn the adjustment screw.

2) After the adjustment, tighten the nuts of speed controllers @2 and @3.

– 14 –

• When the protruding speed of lower knife is slow, thread trimming failure will be caused.

• When the returning speed of lower knife is fast, lower thread clamp failure or uneven needle thread remaining length will be caused.

&

ADJUSTING THE THREAD RELEASE 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.

*A Clearance between click and disk is 0.2 to 0.5 mm. (5 places)

9

7

4

1

2

3

5

!0

45 ± 1mm

*A

6

8

1. Adjusting the disk-rise

.

, turn

1

moves up

3

to 0.2

4

1) Loosen setscrew 2 in adjustment cam adjustment cam or down.

2) Adjust the clearance between the click section of disk-rise plate 3 and thread tension disk to 0.5 mm, and tighten setscrew

3) If the click section of disk-rise plate 3 comes in contact with thread tension disk 4, sewing trouble will be caused. So, be careful.

and disk-rise plate

1

2

2. Adjusting the thread release hook

1) Loosen setscrew tension release rod 6 is spaced 45 ± 1 mm from the top end of take-up thread guide tighten setscrew

2) Loosen setscrew 9, move the position of thread release hook 8 up or down, and the thread remaining length at the start of sewing can be adjusted.

• When the position of thread release hook 8 is raised, the thread remaining length at the start of sewing is decreased and when it is lowered, the thread remaining length at the start of sewing is increased.

• If stitch skipping occurs at the beginning of sewing when using non-elastic thread, properly adjust the remaining length of top-covering thread at the start of sewing using setscrew !0 and minimize the remaining length of looper thread at the start of sewing using screw !1.

. Adjust so that the top end of

5

. Then,

7

.

5

!1

When the thread remaining length at the start of sewing is short, stitch skipping or slip-off of thread from needle eyelet at the start of sewing is apt to occur.

– 15 –

*

. ADJUSTING THE TOP COVERING 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.

1. Adjusting the engagement of knives

1) Adjust so that the engagement of xed knife 1

with moving knife 2 is 0.5 mm.

4

5

2) When adjusting the engagement, loosen setscrews and move knife holder 5 up or down to adjust.

4

2. Adjusting the pressure of

1

!0

2

8

7

0.5 mm

6

3

!2

clamp spring

1) Top covering thread is held with clamp spring

after thread trimming.

2) Holding pressure can be adjusted by loosening nut and turning screw 7.

6

3) Holding pressure is increased when tightening

screw 7 and it is decreased when loosening screw

.

7

4) After the adjustment, tighten nut 6.

5) Make the holding pressure as low as possible

within the range of holding the top covering thread.

3

!1

9

2

9

2

0.5 mm

3. Adjusting the position of the blade point of moving knife

1) Bring the needle bar to its highest position.

2) When hinge screw 8 is lowered, moving knife lowers together.

3) Adjust so that the hook of moving knife 2 enters the recess in the top face of spreader 9 to be brought to the position where the moving knife catches the top covering thread when moving knife 2 is brought to the lowermost position. Then, tighten screws !0, !1 and !2.

Adjust the moving knife vertically so that a

clearance of 0.5 mm is provided between the recess section of spreader 9 and the moving knife, and laterally so that the moving knife 2 is brought to the center of the width of recess in spreader, as illustrated in Figure A.

4) Screws !2 are for adjusting vertical position of the knife, screws !0 for adjusting lateral position of the knife, and screws !1 for adjusting angle of the knife.

Make sure that the moving knife does not interfere with other components such as presser, needle, spreader, etc. within the working range of moving knife 2.

2

Fig. A

– 16 –

3

2

1

4. Adjusting the speed of moving knife

Stroke of air cylinder 1 is 20 mm. Speed of the moving knife can be changed with speed controllers 2 and 3.

1) When you desire to change the protruding speed of moving knife, loosen the nut of speed controller

and turn the adjustment screw.

2

When you desire to change the returning speed of

moving knife, loosen the nut of speed controller and turn the adjustment screw.

2) After the adjustment, tighten the nuts of speed controllers 2 and 3.

When the protruding speed of moving

・

knife is slow, thread trimming failure will be caused.

When the returning speed of moving knife

・

is fast, needle thread clamp failure will be caused.

3

– 17 –

(

. ADJUSTING THE AIR-BLOW WIPER (UT56)

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. Installing the air-blow wiper

1) When using air-blow wiper 1, remove the top covering thread trimmer device.

2) Tighten air-blow wiper 1 with setscrews 2.

3) Perform piping referring to

2

1

DRAWING” p.7

$

.

“

AIR PIPING

.

2. Adjusting the air-blow wiper

3

Adjust the air-blow position of air-blow wiper1.

1) Adjust so that the air outlet of air-blow wiper 1 is positioned in the rear of needle and slightly on the lower side of needle eyelet of the left needle when the needle bar is in the highest position.

2) After the adjustment, temporarily tighten setscrews

.

2

3) Supply air from the air compressor and turn the power ON.

4) When the back part of the pedal of sewing machine is depressed, the presser goes up and simultaneously air blows from air-blow wiper 1. Re-adjust the position of air-blow wiper 1 so that air blows only to the needle thread in the rear of the needle eyelet.

5) After the re-adjustment, tighten setscrews 2.

When air blows in front of the needle,

・

needle thread slips from the needle eyelet. So, be careful.

Adjust the air-blow strength with speed

・

controller 3.

 Handwheelmayrotateuptothexedposi-

・

tion when turning ON the power. So, be careful.

– 18 –

)

ADJUSTING THE NEEDLE THREAD WIPER (UT55)

.

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.

Top end of the clamp spring should not protrude the wiper.

1

4

Center of needle bar

5

8mm

15mm

4mm

4

7

6

3

2

3

8

9

!0

5

1. Adjusting the clamp spring

Adjust the leaf spring which clamps the needle thread after the wiper operates.

1) Install clamp spring 8 on wiper 5 with screw

9

so

that they are in parallel to each other.

2) Fix clamp spring with the screw so that the top end of clamp spring section at the top end of wiper

does not protrude the slanted

8

.

5

2. Installing the needle thread wiper

1) Bring the needle bar to the uppermost position.

2) Make mounting base by tightening screw

3) Adjust so that the lever 3 is horizontally positioned relative to mounting base 1 and a clearance of 4 mm is provided between them. In this state, tighten screw 4.

4) Adjust wiper 5 so that its top end is spaced 15 mm from the center of the needle bar and its height is 8 mm above the top surface of throat plate 6 when wiper 5 is brought to the leftmost position.

5) Adjust the position of the top end of wiper 5 by means of screw

7

wiper 5 by means of screw !0 respectively.

6) After the completion of the adjustment, tighten screws 2.

When the solenoid operates, the solenoid shaft moves forward by 0.9 mm while rotating. To adjust the solenoid, rotate it while pulling lever tion of the adjustment, activate the solenoid to check that it does not interfere with other parts such as the presser foot and needle in the operating range of wiper

level and temporarily x it

1

at the center of the slot.

2

and the height of the top end of

toward you. After the comple-

3

.

5

– 19 –

_

. MAINTENANCE

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. Cleaning the motor fan

1

2

3

Open the motor cover Clean up the periphery of the motor fan 3 and the motor cover 1. After the completion of cleaning, re-install the motor fan

and the motor cover 1.

3

and remove the screws 2.

1

– 20 –

JUKI MF-7900D/UT55, MF-7900D/UT57, MF-7900D/UT56, MF-7900/UT55, MF-7900/UT57 Instruction Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

CONTENTS

1. Installing the presser lifting cylinder

2. Installing the air regulator

3. Installation and setting SC-921

(1) Installing the SC-921 on the table ( Table-mount type )

(2) Installing the SC-921 on the table ( Semi-submerged type )

(3) Connecting the cords

(4) Setting procedure of the machine head

(5) Setting the lower stop position of the needle bar

1. Piping of the thread trimmer device (UT57)

2. Piping of the thread trimmer device (UT55)

3. Piping drawing for air blow (UT56)

4. Adjusting the air regulator

1. Adjusting the thread trimmer air cylinder

2. Adjusting the Lower knife

3. Adjusting the position of clampAdjusting the position of clamp pressure adjusting spring

4. Adjusting the knifeAdjusting the knife engagement and the knife pressure adjusting spring

5. Adjusting the pressure of clamp spring

6. Initial position of the looper thread trimmer mechanism

7. Adjusting the stopper

8. Adjusting the height of the lower knife

9. Adjusting the lower knife holder guide

10. Adjusting the longitudinal position of the blade point of lower knife

11. Adjusting the thread trimmer sensor

12. Adjusting the speed of looper thread trimmer

1. Adjusting the disk-rise

2. Adjusting the thread release hook

1. Adjusting the engagement of knives

3. Adjusting the position of the blade point of moving knife

4. Adjusting the speed of moving knife

1. Installing the air-blow wiper

2. Adjusting the air-blow wiper

1. Adjusting the clamp spring

2. Installing the needle thread wiper

1. Cleaning the motor fan