JUKI MB-1800, MB-1800A Engineer's Manual

R

Dry-head Type, High-speed, Computer-controlled, Single Thread,
Chainstich Button Sewing Machine
(with Automatic Thread Trimmer and Knot-tying Mechanism)

MB-1800
MB-1800A

ENGINEER’S MANUAL

29345105

No.00

PREFACE

This Engineer’s Manual is written for the technical personnel who are responsible for the service and maintenance
of the machine.
The Instruction Manual for these machines intended for the maintenance personnel and operators at an apparel
factory contains operating instructions in detail. And this manual describes “Standard Adjustment”, “Adjustment
Procedures”, “Results of Improper Adjutment”, and other important information which are not covered by the
Instruction Manual. It is advisable to use the revevant Instruction Manual and Parts List together with this
Engineer’s Manual when carrying out the maintenance of these machines.

CONTENTS

1. SPECIFICATIONS...................................................................................................................................1

2. NAME OF EACH COMPONENT.............................................................................................................2

(1) Name of the main unit ................................................................................................................................................. 2

3. OPERATION OF THE SEWING MACHINE ............................................................................................3

(1) Names of the operation panel switches .................................................................................................................... 3

(2) Pattern table ................................................................................................................................................................. 4

(3) How to operate and use the memory switch (User level) ........................................................................................ 5

4. STANDARD ADJUSTMENT ...................................................................................................................6

(1) Height of the needle bar.............................................................................................................................................. 6

(2) Positioning the needle and the looper....................................................................................................................... 6

(3) Timing the travel of the yoke slide............................................................................................................................. 8

(4) Timing of the tension disc No. 2 ................................................................................................................................ 8

(5) Lift and pressure of the button clamp ..................................................................................................................... 10

5. ADJUSTMENT OF THE THREAD TRIMMING MECHANISM ..............................................................10

(1) The mechanism and the name of each component of the thread trimmer .......................................................... 10

(2) Adjusting the position of the moving knife............................................................................................................. 12

(3) Adjusting the height of the thread separating claw of the moving knife ............................................................. 12

6. PROCEDURES IN DISASSEMBLING AND ASSEMBLING ................................................................14

(1) Name of each component ......................................................................................................................................... 14

(2) Disassembling the circuit board .............................................................................................................................. 16

(3) Disassembling the machine arm and bed ............................................................................................................... 18

(4) Disassembling the looper shaft ............................................................................................................................... 20

(5) Disassembling the driving shaft .............................................................................................................................. 22

7. ADJUSTMENT OF THE SENSORS......................................................................................................26

(1) Adjusting the starting sensor................................................................................................................................... 26

(2) Adjusting the presser lifter sensor .......................................................................................................................... 26

(3) Adjusting the feed origin sensor ............................................................................................................................. 28

(4) Adjusting the presser lifter stopper......................................................................................................................... 28

8. HOW TO OPERATE AND USE THE MEMORY SWITCH (SERVICE LEVEL) ....................................30

(1) Memory switch function table .................................................................................................................................. 31

9. HOW TO OPERATE AND USE THE INPUT CHECK MODE FUNCTION ........................................... 33

(1) INPUT CHECK CORRESPONDENCE TABLE .......................................................................................................... 34

10. HOW TO OPERATE AND USE THE ALL CLEAR FUNCTION ........................................................... 35

11. PARTS TO BE GREASESD..................................................................................................................36

12. ERROR LIST .........................................................................................................................................37

13. CHANGE-OVER OF THE POWER SOURCE VOLTAGE .................................................................... 38

14. CAUSE OF TROUBLES AND THE CORRECTIVE MEASURES.........................................................39

(1) Thread trimming troubles and the corrective measures ....................................................................................... 39

(2) Cause of troubles and the corrective measures for MB-1800 ............................................................................... 40

15. CIRCUIT BOARD DIAGRAM ................................................................................................................41

(1) MAIN circuit board..................................................................................................................................................... 41

(2) PWR circuit board ..................................................................................................................................................... 42

(3) PANEL circuit board.................................................................................................................................................. 42

16. BLOCK DIAGRAM 1/2 ..........................................................................................................................43

17. CONNECTION DIAGRAM AND CIRCUIT DIAGRAM ..........................................................................45

(1) Power connection diagram....................................................................................................................................... 45

(2) Sensor connection diagram ..................................................................................................................................... 46

(3) Motor circuit diagram ................................................................................................................................................ 47

(4) Encoder circuit diagram ........................................................................................................................................... 48

(5) Solenoid circuit diagram........................................................................................................................................... 48

18. DRAWING OF THE TABLE ..................................................................................................................49

−1−

1. SPECIFICATIONS

1) Sewing area : X (lateral) direction 10 mm
Y (longitudinal) direction 6.5 mm (0.2 mm pitch)

2) Max. sewing speed : 1,800 rpm

3) Feed motion of button clamp : Intermittent feed (2-shaft drive by stepping motor)

4) Needle bar stroke : 48.6 mm

5) Needle : TQx7, TQx1 (TQx7 #16 at the time of delivery)

6) Button size : 10 to 28 mm

7) Lift of button clamp : Standard 10 mm Max. 14 mm

8) Memory of pattern data : EEP-ROM (32K byte)

9) Enlargement/reduction system : Increase/decrease of stitch length system

10) Limitation of sewing speed : Sewing speed can be optionally limited to 400 to 1,800 rpm with the
up/down key. (Adjustable in 100 rpm unit)

11) Pattern selection function : 1 to 99 patterns can be specified by selecting the pattern Nos.

12) Memory back-up : In case of a power interruption, the pattern being used will be
automatically stored in memory.

13) Sewing machine motor : 100W servo motor (direct-drive)

14) Dimensions of machine head : W : 240 mm L : 550 mm H : 360 mm

15) Mass : 25 kg

16) Power consumption : 150 W

17) Operating temperature range : 5 to 35˚C

18) Operating humidity range : 35 to 85% (no dew condensation)

19) Line voltage : Rated voltage ±10% 50/60 Hz

20) Noise : Workplace - related noise at sewing speed
n= 1,800 min-1 : LPA ≦ 80 dB(A)
Noise measurement according to DIN 45635-48-B-1.

＊ Reduce the max. sewing speed in accordance with the sewing conditions.

−2−

2. NAME OF EACH COMPONENT

(1) Name of the main unit

• Machine head

• Electrical
components

• Operation panel

• Thread stand

• Button tray

• Power switch

• Starting pedal

−3−

3. OPERATION OF THE SEWING MACHINE

(1) Names of the operation panel switches

1 Set ready switch

This switch is used when making the sewing
machine from setting status to sewing
possible status.

2 Button clamp lifting switch

This switch performs up/down of the button
clamp.

3 Stitch shape selection LED

4 Stitch shape selection switch

This switch is used when changing the stitch
shape.

5 ＋/ Forward switch

This switch increases the set value or performs
traveling forward when confirming the feed.

6 −/ Backward switch

This switch decreases the set value or performs
traveling backward when confirming the feed.

7 Item selection switch

This switch is used when selecting the item
desired to be changed.

8 Item selection LED

9 Reset switch

This switch returns the various set values
to the original status or performs release
when an error occurs.

!0 Display section A

−4−

(2) Pattern table

Three same sewing sizes and numbers of stitches for each stitch shape have been stored in pattern Nos. 1 to
51 at the time of delivery.
By selecting sewing size and number of stitches from the table below, the stitch shape can be changed to the
three different kinds of patterns of the same stitch shape and be stored in memory.

Pattern No.

1
2
3

4
5
6

7
8
9

10
11
12

13
14
15

16
17
18

19
20
21

22
23
24

25
26
27

28
29
30

31
32
33

34
35
36

37
38
39

40
41
42

43
44
45

46
47
48

49
50
51

4-holed
( , crossover stitch : with)

4-holed
( , crossover stitch : without)

4-holed
( X, crossover stitch : with)

4-holed
( X, crossover stitch : without)

4-holed
( Z, crossover stitch : with)

2-holed (crosswise)

2-holed (lengthwise)

4-holed
( , crossover stitch : with)

4-holed
( , crossover stitch : without)

3-holed ( )

3-holed ( )

3-holed ( )

3-holed ( )

2-holed
(crosswise) label attaching

Wrapped-around
(crosswize size : 4 mm)

Wrapped-around
(crosswise size : 5 mm)

Wrapped-around
(crosswise size : 6 mm)

Initial value

2.6

2.6

2.6

2.6

2.6

2.6

2.6

2.6

2.6

2.6

2.6

2.6

2.6

10.0

2.6

2.6

2.6

Range

2.0 to 6.5

2.0 to 6.5

2.0 to 6.5

2.0 to 6.5

2.0 to 6.5

2.0 to 6.5

2.0 to 6.5

2.0 to 6.5

2.0 to 6.5

2.6, 2.8, 3.0

2.6, 2.8, 3.0

2.6, 2.8, 3.0

2.6, 2.8, 3.0

6.0, 8.0, 10.0

0.0 to 6.5

0.0 to 6.5

0.0 to 6.5

Unit

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

2.0

0.2

0.2

0.2

Initial value

15

16

15

16

15

8

8

15

16

17

17

17

17

5

16

16

16

Range

15, 19, 23, 27

16, 20, 24, 28

15, 19, 23, 27

16, 20, 24, 28

15, 19, 23, 27

8, 10, 12, 14

8, 10, 12, 14

15, 19, 23, 27

16, 20, 24, 28

17, 23

17, 23

17, 23

17, 23

5, 7

6, 10, 16

6, 10, 16

6, 10, 16

Stich size (mm) Number of stitches

Stich shape

−5−

(3) How to operate and use the memory switch (User level)

1) The speed up to 3rd stitch can be set so that the sewing speed at the start of sewing is controlled and the
stitch is stabilized.

2) Effective/ineffective of the knot-tying functon can be selected.

3) Operating/non operating of the wiper can be selected.
In case the wiper is installed and set to the non-operating setting, when the pattern without crossover
thread is selected, the wiper works only when the crossover thread is trimmed, and it does not work after
thread trimming at the time of completion of sewing.
In case of the pattern with crossover thread as well, the wiper does not work after thread trimming at the
time of completion of sewing with this setting.
In case of the setting of operating the wiper, the wiper always works at the time of thread trimming.

1 Starting of the memory switches

In the state that ＋/− switches 2 are simultaneously
pressed, turn ON the power, and the memory switches
are in the state of setting.

At this time, “ ” is displayed in display section A 3.
Press set ready switch 5 and all 5 stitch shape
selection LEDs 9 flash on and off. This state means

that the memory switches are being inputted.

2 Setting procedure of the memory switches

There are the memory switches 1 to 8.
Switch N0. “ ” is displayed in the display section A 3 and item selection LED !0 of the pattern No.

lights up. In this state, press item selection switch 4, and the memory switch No. and the description
are alternately displayed in display section A 3.

In the state that the memory switch No. is displayed, press the ＋ switch 8 and the memory switch No.
increases by one.
When the description of the memory switch is displayed, item selection LED !0 of the pattern No. goes
off.

When setting is completed, turn OFF the power. Return ON the power to return to the normal setting state.

Remarks
400 to 1,800 rpm
400 to 1,800 rpm

400 to 1,800 rpm

400 to 1,800 rpm
400 to 1,800 rpm

400 to 1,800 rpm

Switch No.

1
2
3
4
5
6
7
8

Description
Speed of 1st stitch of soft start
Speed of 2nd stitch of soft start
Speed of 3rd stitch of soft start
Speed of 1st stitch after trimming crossover thread
Speed of 2nd stitch after trimming crossover thread
Speed of 3rd stitch after trimming crossover thread
Knot-tying function 0 : Ineffective 1 : Effective
Wiper operation 0 : Non operating 1 : Operating

Initial setting
18＊ 100 [rpm]
18＊ 100 [rpm]
18＊ 100 [rpm]
18＊ 100 [rpm]
18＊ 100 [rpm]
18＊ 100 [rpm]

1 (Operating)

0 (Non operating)

Setting range

4 to 18
4 to 18
4 to 18
4 to 18
4 to 18
4 to 18

0.1

0.1

1

2

3

4

5

6

7

8

9

!0

−6 −

(1) Height of the needle bar

The upper engraved line of the two engraved lines for TQx1 and TQx7 should be aligned with the bottom of
the lower bushing when the needle bar is at its lowest position.

4. STANDARD ADJUSTMENT

(2) Positioning the needle and the looper

1) Looper timing
When the needle bar is ascending from its lowest
position and the lower engraved line on the needle
bar is aligned with the bottom of the lower bushing,
the looper’s blade point should coincide with the
center of the needle.
(When the needle bar is ascending.)

2) Clearance between the needle and looper
The clearance is 0.05 to 0.1 mm when the looper’s
blade point coincides with the center of the needle.

3) Clearance between the needle guide and needle
The clearance between the needle guide and
needle is 0.05 to 0.1 mm when the needle bar is at
its lowest position.

Height of the needle bar

For TQx1

For TQx1

Engraved line
(upper engraved line)

Lower
bushing

Looper timing

Lower bushing

Engraved line

Looper’s blade
point coincides
with center of
needle.

Clearance between needle and looper

0.05 to 0.1 mm

Looper’s blade point

Clearance between needle guide and looper

Needle guide

0.05 to 0.1 mm

Screw

1

2

3

4

1

2

3

4

Standard Adjustment

−7 −

™ If the needle bar is too high, skipped

stitches will be produced.
If the needle bar is too low, the needle
will come in contact with the looper.

1) Adjusting the looper timing
™ Loosen the two screws 3 in the looper and cam sleeve

and adjust in the rotating direction of the looper and
cam sleeve so that the looper’s blade point aligns with
the center of the needle when the lower engraved line
of the needle bar is aligned with the bottom of the lower
bushing. Then tighten the screws 3.

2) Clearance between the needle and looper

Loosen two screws 4 in the looper support ring and adjust
in the longitudinal position of the looper when the looper’s
blade point is aligned with the center of the needle. Then
tighten the screws 4.

3) Clearance between the needle guide and needle

Loosen the screw 2 in the needle guide 1 and adjust in
the longitudinal position of the needle guide 1 so that the
clearance between the needle guide 1 and needle should
become 0.05 to 0.1 mm when the needle bar is at its lowest
position. Then tighten the screw 2.

™ If the clearance between the needle

and looper is too excessive, it is likely
to produce skipped stitches. If the
clearance is too small, in accordance
with the material used, the needle will
come in contact with the looper
resulting in needle breakage and
looper’s blade point breakage.

™ For thick materials and overlapped

sections, adjust the clearance between
the needle guide and needle so that
the needle guide touches the needle
by 0.1 to 0.2 mm.

1) Slightly loosen knob 1 and turn cover 2 in the direction

of the arrow and you will find hand pulley 3.

2) Turn the hand pulley by hand, loosen setscrew 4 in the

needle bar thread-take up lever and adjust so that the
upper engraved line of the two engraved lines on the
needle bar aligns with the bottom of the lower bushing
when the needle bar is at its lowest position.

Adjustment Procedures Results of Improper Adjustment

−8 −

(3) Timing the travel of the yoke slide

1) Crosswise travel timing of the yoke slide

The height of the descending needle bar is 53 to 58
mm when the yoke slide advances and begins to
travel from the right to the left (TQx7).
(In case of TQx1, 43 to 48 mm)

2) Lengthwise travel timing of the yoke slide

The yoke slide should go back immediately after
the blade point of the looper has passed the thread
triangle. And, it is good for the looper to go back
like a slant line of the movement of the triangle.

3) Lengthwise positioning of the yoke slide

Position the yoke slide so that the blade point of
the looper passes through the center of the thread
triangle.
(Use a 4-hole button, 9 or 10 stitches for positioning.)

(4) Timing of the tension disc No. 2

The tension disc No. 2 should float when the height of ascending needle bar becomes 54 to 57 mm.
(In case of TQx1, 44 to 47 mm)

Needle bar

53 to 58 mm

Advances and begins to
travel from right to left.

It is good for
the looper to
go back like
a slant line.

Yoke slide

(Begins to travel from right to left.)

Blade point of looper

54 to 57 mm

Begins to float

Screw driver

Needle bar

Standard Adjustment

−9 −

™ For adjusting the timing of the travel of the yoke slide,

align the engraved marks of the loop positioning finger
cam and the triangle loop positionig finger cam with the
engraved mark of the cam and looper sleeve after
completing the adjustment of looper so that the engraved
marks are on a straight line. Then temporarily tighten the
screw.

1) Adjust the crosswise travel timing of the yoke slide in the

rotational direction of the triangle loop positioning finger
cam.
When the timing is higher than 58 mm (48 mm), adjust
the timing in the rotational direction of the cam.
And when it is lower than 53 mm (43 mm), adjust in the
reverse rotational direction.
The center of the cam is aligned with the center of the
yoke slide support in the longitudinal position of the cam.

2) Adjust the lengthwise travel timing of the yoke slide in the

rotational direction of the loop positioning finger cam.
For the triangle movement of the yoke slide, it is good for
the yoke slide to go back in a slant line. When the yoke
slide goes back like a swollen line, adjust the cam in the
reverse rotational direction, and when it goes back like a
hollow line inside, adjust the cam in the rotational direction.

3) Adjust the longitudinal position of the yoke slide by moving

the loop positioning finger cam in the lengthwise direction.

™ If the triangle loop positioning finger

cam begins to travel too late, thread
breakage, thread remaining, baloon
stitch, and insufficient tightness of
stitches will result. On the contrary, if
it begins to move too early, the needle
will come in contact with the yoke slide.

™ If the loop positioning finger cam

begins to go back too early, the retreat
of the yoke slide will become like a
swollen line and the looper will hook
the thread twice.

™ On the other hand, if it begins to retreat

too late, its retreat will become like a
hollow line and the needle will come in
contact with the yoke slide.

™ If the longitudinal position of the yoke

slide is improper, the looper will hook
the thread twice or the needle will come
in contact with the yoke slide.

™ Loosen the adjusting nut of the tension post No. 2 and

insert a screwdriver into the tension post No. 2 to adjust
the timing.
The timing of the start of floating is when the thread
tension is lost after passing the thread through the thread
tension No. 2, holding it with fingers and turning the
handwheel by ha

™ If the thread tension is released too

early, thread remaining and/or poor
tightness of stitches will result.
On the other hand, if the timing of
thread tension release is too late,
thread will break.

Looper

Engraved points

Triangle loop
positioning
finger cam

Cam and looper sleeve

Loop positioning finger cam

Yoko slide retreats
like a swollen line.

Yoko slide retreats

like a hollow line.

Screw driver

Timing of start of floating
is when thread tenshon is
lost at the time of needle
bar ascending.

Nut

Adjustment Procedures Results of Improper Adjustment

−10 −

(5) Lift and pressure of the button clamp

1) Lift of the button clamp
A Standard : 12 mm

Max. : 9 mm

2) Pressure of the button clamp

Adjust the position of the pressure adjusting nut to
4 to 5 mm.

4 to 5 mm

5. ADJUSTMENT OF THE THREAD TRIMMING MECHANISM

(1) The mechanism and the name of each component of the thread trimmer

Throat plate

Presser lifter solenoid

Thread trimming arm

Thread trimming lever

Presser lifter sensor

Presser lifter link

Presser lifter lever

1

2

3

A

1

2

Standard Adjustment

−11 −

1) The knife moves in accordance with the lifting of the button

clamp. Therefore, the length of the remaining thread on
the wrong side of a fabric depends upon the height of the
button clamp at which the thread is trimmed.
For the adjustment, insert something of 10 mm thick into
section A and make a state that button clamp jaw levers
1 are lifted .
Loosen screw 2 and tighten screw 2 to fix the button
clamp in the state that lifting hook 3 is pressed to the
lower side.

2)

Make adjustment by turning the pressure adjusting nut 1.

™ Increasing the lifting amount of the

button clamp will increase the length
of the remaining thread. Especially in
case of MB-372, thread tightness
becomes strong at the end of sewing
resulting in thread breakage and thread
slip-off.

™ If the lifting amount of the button clamp

is too low, the length of the remaining
thread will become short resulting in
thread slip-off.

™ If the pressure of the button clamp is

too low, the thread end at the start of
sewing will come out on the wrong side
of the fabric unevenly by 10 to 20 mm.

Adjustment Procedures Results of Improper Adjustment

−12 −

(2) Adjusting the position of the moving knife

Adjust the position so that the distance between the thread trimming connecting plat (front) and the edge of
the slot in the throat plate should be 12 to 13 mm when the button clamp is at its highest position.

(3) Adjusting the height of the thread separating claw of the moving knife

Make adjustment so that the clearance between the thread separating claw 1 and the looper 2 should
become 0.5 to 0.7 mm.

0.5 to 0.7 mm

Top end of thread separation nail

1

2

3

4

5

6

7

8

9

1

2

Standard Adjustment

−13 −

1) Remove cover 1 with setscrew 2.

2) In order to place thread trimming connecting plate A 9 to

the most advanced position, lift the presser lifter lever to
such an extent that roller 4 and hook 5 of presser lifter
lever 3 come in contact with each other and insert spanner
6 as shown in the figure on the left.

3) Insert gauge 7 into the end face of the throat plate groove,

loosen screws 8, make the top end of thread trimming
connecting plate A 9 come in contact with gauge 7, and
tighten screws 8.

™ If the thread separating claw is too high,

the claw may fail to separate the thread
on the needle from that on a fabric. As
a result, thread may not be trimmed,
or the both threads are trimmed
together, causing thread slippage from
the needle in the subsequent stitching
start.

™ If this dimension is excessively large,

the thread trimming timing is delayed
and the remaining thread on the wrong
side of cloth is lengthened.
If the dimension is excessively small,
the thread trimming timing

becomes too

early, thread trimming

failure such as
poor tightness of stitche (easily frayed)
at the last stitch, simultaneous thread
trimming of two threads due to the
failure of thread separation, no thread
trimming, etc. is apt to occur.

™ Make adjustment by bending the thread separating claw

1.

Adjustment Procedures Results of Improper Adjustment