JUKI MOL-254 Quick start guide

R
ENGINEER’S MANUAL
29341005
No.00
2-needle, Automatic Belt-loop Attaching Machine
MOL-254

PREFACE
This Engineer’s Manual is written for the technical personnel who are responsible for the service and maintenance
of the sewing machine. This manual describes “Adjustment Procedure”, “Results of Improper Adjustment”, and
other functions which are not covered by the Instruction Book intended for the maintenance personnel and
sewing operators at a sewing factory.
All personnel engaged in repair of MOL-254 are required to carefully read Section 2 “Standard Adjustment”
which contains important information on the maintenance of MOL-254.
The “Standard Adjustment” consists of two parts; the former part presents illustration and simplified explanation
for the convenience of reconfirmation of the required adjustment values in carrying out actual adjustment after
reading this manual once; and the latter part provides “Results of Improper Adjustment” in which sewing and/or
mechanical failures, and the correcting procedures are explained for those persons who perform such adjustment
for the first time.
It is advisable to use “MOL-254 Parts Book” together with this Engineer’s Manual.

CONTENTS
1. SPECIFICATIONS ......................................................................................1
2. NAMES AND FUNCTIONS OF COMPONENTS........................................3
[1] Names and functions of the main unit.................................................................. 3
[2] Names and functions of operation box panel...................................................... 4
3. TIMING CHART ..........................................................................................6
4. STANDARD ADJUSTMENT ......................................................................7
[1] Machine head components.................................................................................... 7
(1) Adjustment of the main shaft components .................................................................................... 7
1) Removing the play of main shaft................................................................................................ 7
2) Installing the main shaft coupling ............................................................................................... 7
3) Adjusting the main shaft sensor ................................................................................................. 9
4) Stretching the timing belt (Main shaft-to-hook driving shaft for the front side timing) ................ 9
5) Adjusting the idler .................................................................................................................... 11
(2) Adjusting the hook driving shaft components.............................................................................. 11
1) Adjusting the longitudinal position of the oscillator .................................................................. 11
2) Adjusting the backlash of the oscillator gear............................................................................ 13
3) Removing the play of the hook driving shaft ............................................................................ 13
(3) Adjusting the thread trimmer mechanism components ............................................................... 15
1) Adjusting the position of the thread trimmer cam.................................................................... 15
2) Adjusting the thread trimmer link stopper screw ..................................................................... 15
3) Adjusting the thread trimming cylinder (front side).................................................................. 17
4) Position of the thread trimmer shaft .........................................................................................19
5) Position of the cam follower stopper ........................................................................................ 19
6) Position of the thread trimming solenoid .................................................................................. 21
7) Adjusting moving and counter knives ...................................................................................... 23
8) Height of the moving and counter knives ................................................................................. 25
9) Parallelism of the blade tip of the counter knife ....................................................................... 25
10) Adjusting the thread trimmer cam timing (only for this side) .................................................. 27
(4) Adjusting the tension release mechanism components .............................................................. 27
1) Installing position of the tension release notch ........................................................................ 27
2) Position of the tension release stopper .................................................................................... 29
3) Releasing amount of the thread tension disk ........................................................................... 29
(5) Adjusting the sensor components ............................................................................................... 31
1) Adjusting the Y origin sensor ................................................................................................... 31
2) Adjusting the X origin sensor ................................................................................................... 31
(6) Adjusting the feed mechanism components................................................................................ 33
1) Adjusting the position of the X/Y motors .................................................................................. 33
2) Adjusting the position of the cloth presser foot ........................................................................ 35
3) Adjusting the position of the cloth presser lower plate ............................................................. 37
4) Adjusting the lift of the cloth presser foot .................................................................................37
(7) Adjusting the position of the needle bar and the hook ................................................................ 39
1) Adjusting the height of the needle bar ..................................................................................... 39
2) Changing the position of the throat plate (hook base) (Adjustment of the 1st hook) ............... 39
3) Adjusting needle-to-inner hook timing (Same adjustment for this side and far side) ............... 41
4) Adjusting the position of the shuttle upper spring (Same adjustment for this side and far side) ..... 43
5) Form of the inner hook presser ................................................................................................ 43
6) Adjusting the timing of the hook on this side............................................................................ 45
7) Adjusting procedure of the hook removing sensor................................................................... 47
8) Adjusting the play in the hook removing ball screw ................................................................. 49
(8) With regard to sewing.................................................................................................................. 51
1) Adjusting the thread take-up spring ......................................................................................... 51
2) Adjusting the position of the wiper ........................................................................................... 53

(9) Disassembling/assembling of components ................................................................................. 55
1) Disassembling/assembling of the timing belt ........................................................................... 55
2) Disassembling/assembling of the throat plate ......................................................................... 69
3) Disassembling/assembling of the hook removing cross roller ................................................. 71
4) Disassembling/assembling of the ball spline ........................................................................... 73
[2] Device components.............................................................................................. 75
(1) Loop cut components .................................................................................................................. 75
1) Adjusting the height of the loop cut knife unit .......................................................................... 75
2) Adjusting the cross cut angle of the loop cut knife................................................................... 77
3) Adjusting the position of the loop cut center ............................................................................ 79
4) Changing the straight cutting ................................................................................................... 81
5) Adjusting the loop cut cylinder sensor ..................................................................................... 87
6) Adjusting the installation of the belt loop splice sensor............................................................ 89
(2) Loop clamp feed components ..................................................................................................... 93
1) Adjusting the loop clamp base plate front sensor .................................................................... 93
2) Adjusting the loop clamp base plate rear sensor ..................................................................... 95
3) Adjusting the loop clamp lever loop existence sensor ............................................................. 97
4) Adjusting the opening amount of the loop clamp base ............................................................ 99
5) Adjusting the position of the loop clamp feed unit.................................................................... 99
(3) Belt loop feed components ........................................................................................................ 101
1) Adjusting the height (clearance) of the loop feed roller.......................................................... 101
2) Adjusting the pressure of the loop feed roller ........................................................................ 103
3) Adjusting the tension of the loop feed roller belt .................................................................... 105
(4) Belt loop supply components .................................................................................................... 107
1) Adjusting the tension of the loop supply belt.......................................................................... 107
2) Adjusting the play in the rotation of the loop supply slide base ............................................. 109
3) Adjusting the loop supply slide base sensor .......................................................................... 111
4) Adjusting the height of the fork (up/down of this side and far side) ....................................... 113
5) Adjusting the height of the fork (up/down of the unit)............................................................. 115
6) Adjusting the position of the fork and the needle ................................................................... 117
(5) Adjusting the air speed controller .............................................................................................. 119
1) Cam up/down cylinder ........................................................................................................... 119
2) Belt presser removing base cylinder ...................................................................................... 119
3) Belt presser cylinder............................................................................................................... 119
4) Loop pull-out cylinder (Optional) ............................................................................................ 121
5) Fullness cylinder (Optional) ................................................................................................... 121
6) Needle cooler (Optional) ........................................................................................................ 121
(6) Adjusting the pressure reduction controller ............................................................................... 123
1) Loop folding cylinder .............................................................................................................. 123
(7) Disassembling/assembling ........................................................................................................ 125
1) Disassembling/assembling of the loop cut knife and the counter knife.................................. 125
2) Disassembling/assembling of the loop cut knife drive components ....................................... 127
3) Disassembling/assembling of the loop supply ....................................................................... 129
4) Disassembling/assembling of the loop supply cam components ........................................... 131
5) Disassembling/assembling of the loop supply belt components ............................................ 133
6) Disassembling/assembling of the loop supply unit ................................................................ 135
7) Disassembling/assembling of the loop feed roller components ............................................. 137
8) Disassembling/assembling of the belt presser unit ................................................................ 139
[8] Installing of the optional parts. ......................................................................... 141
1) Installing of the fullness device .............................................................................................. 141
2) Installing of the needle cooler ................................................................................................ 145
3) Installing of the thread breakage detector device .................................................................. 147
4) Installing of the loop pull-out device ....................................................................................... 149
5) Installing of the air gun ........................................................................................................... 151

5. OPERATION BOX PANEL.....................................................................153
[1] Operating procedure of the maintenance screen............................................ 153
(1) [CA] Setting of starting angle of the 1st hook thread trimming cylinder drive............................ 153
(2) [CB] Setting of ending angle of the 1st hook thread trimming cylinder drive............................. 153
(3) [CC] Setting of starting angle of the 2nd hook thread trimming solenoid drive ......................... 153
(4) [CD] Setting of the speed of the loop clamp feed unit ............................................................... 153
(5) [CE] Setting of the machine head X-Y drive timing ................................................................... 153
(6) [CF] Setting of the period of time during which the cloth presser foot stops ............................. 154
(7) [CG] Setting of traveling backward distance of the fork at low speed at the time of set back ... 154
(8) [CH] Setting of the length of time at the time of change-over of the supply slide base cam ..... 154
(9) [CI] Setting of waiting time when the supply slide base travels backward to the end ............... 154
(10) [CJ] Function of individual operation of the machine head...................................................... 155
(11) [CK] Setting of the number of revolutions of the machine head motor .................................... 155
(12) [CL] Setting of the machine head motor operating time .......................................................... 155
(13) [CM] Setting of the machine head motor stop time ................................................................. 155
(14) [CN] Setting of the position compensation of the machine head and the supply device......... 155
[2] Initial setting table .............................................................................................. 156
6. DIP SWITCHES ON THE CIRCUIT BOARD..........................................158
[1] DIP switches on MAIN circuit board ................................................................. 158
[2] DIP switches on SDC circuit board................................................................... 159
7. PARTS TO BE APPLIED WITH GREASE AND LOCKTITE PAINT .....160
[1] Needle bar components ..................................................................................... 160
[2] Main shaft components...................................................................................... 161
[3] Feed mechanism components .......................................................................... 162
[4] Tension release and thread trimmer mechanism components...................... 163
[5] Thread presser components ............................................................................. 164
[6] Hook base components (1)................................................................................ 165
[7] Hook base components (2)................................................................................ 166
[8] Hook driving shaft components........................................................................ 167
[9] Hook move components.................................................................................... 168
[10] Belt loop supply components ......................................................................... 169
[11] Belt receiver components................................................................................ 170
[12] Belt loop feed components.............................................................................. 171
[13] Clamp feed components .................................................................................. 172
[14] Knife components ............................................................................................ 173
[15] Supplying device base components............................................................... 174
8. PNEUMATIC CIRCUIT DIAGRAM .........................................................175
9. CONTROL BOX......................................................................................176
[1] Explanation of components............................................................................... 176
(1) MAIN CIRCUIT BOARD ............................................................................................................ 177
(2) SDC CIRCUIT BOARD ............................................................................................................. 178
(3) Power circuit board.................................................................................................................... 179
(4) PMDC circuit board ................................................................................................................... 179
(5) Transformer............................................................................................................................... 179
(6) Fan motor .................................................................................................................................. 179
(7) Power change-over tap ............................................................................................................. 179
(8) F1 fuse (6.3AT) ......................................................................................................................... 179

(9) F5 fuse (6.3AT) ......................................................................................................................... 179
(10) F6 fuse (6.3AT) ....................................................................................................................... 179
[2] Replacing the parts ............................................................................................ 180
(1) Replacing EPROM .................................................................................................................... 180
(2) Replacing the fuse..................................................................................................................... 181
[3] Change of the power specifications ................................................................. 182
(1) [General export]......................................................................................................................... 182
1) Setting of the power voltage specifications............................................................................ 182
2) Setting of the phase of power (Remodelling of the power cord) ............................................ 182
(2) [For CE and general export, high voltage]................................................................................. 183
1) Setting of the power voltage specifications............................................................................ 183
2) Setting of the phase of the power (Remodelling of the power cord) ...................................... 184
10. POWER SWITCH .................................................................................185
[1] Power switch for domestic and general export (low voltage) ........................ 185
[2] Power switch for general export (low voltage) ................................................ 185
[3] Power switch for CE marking and general export (high voltage) .................. 186
[4] Power switch for CE marking ............................................................................ 186
11. NAME AND INSTALLING POSITION OF THE SWITCH SENSOR ....187
12. CIRCUIT DIAGRAM .............................................................................188
[1] Block diagram..................................................................................................... 188
[2] Wiring diagram.................................................................................................... 191
(1) Power cable asm. circuit diagram A (for domestic and general export (low voltage))............... 191
(2) Power cable asm. circuit diagram B (for CE and general export (high voltage))....................... 191
(3) Transformer asm. circuit diagram.............................................................................................. 191
(4) DC power cable asm. circuit diagram........................................................................................ 192
(5) SDC•I/F cable asm. circuit diagram........................................................................................... 192
(6) PMDC•I/F cable asm. circuit diagram........................................................................................ 193
(7) CN10 wiring cable circuit diagram............................................................................................. 193
(8) CN13 wiring cable circuit diagram............................................................................................. 193
(9) CN15 wiring cable circuit diagram............................................................................................. 193
(10) CN11 wiring cable circuit diagram........................................................................................... 194
(11) CN12 wiring cable circuit diagram........................................................................................... 194
(12) CN14 wiring cable circuit diagram........................................................................................... 195
(13) X/Y table origin sensor wiring cable circuit diagram................................................................ 196
(14) SDET sensor wiring cable circuit diagram............................................................................... 196
(15) Stepping motor wiring cable circuit diagram............................................................................ 197
(16) X/Y table stepping motor wiring cable circuit diagram............................................................. 197
(17) Fork move servo motor wiring cable circuit diagram ............................................................... 198
(18) Thread trimming Mg. wiring cable circuit diagram................................................................... 198
(19) Solenoid valve wiring cable circuit diagram............................................................................. 199
[3] Sensor input/output table .................................................................................. 200
13. TROUBLES AND CORRECTIVE MEASURES....................................201
[1] Machine head components................................................................................ 201
[2] Device components............................................................................................ 213
(1) Trouble and corrective measure................................................................................................ 213
(2) Corrective measures for the dog-eared belt loop ...................................................................... 219
[3] Electrical components ....................................................................................... 221

Please do not hesitate to contact our distributors or agents in your area for further information when necessary.
＊The description covered in this engineer’s manual is subject to change for improvement of the
commodity without notice.
99 · 11 Printed in Japan (E)
R
INTERNATIONAL SALES H.Q.
8-2-1, KOKURYO-CHO,
CHOFU-SHI, TOKYO 182-8655, JAPAN
PHONE : [phone] to 4005
FAX : [phone] • 4914 • 4984
TELEX : J22967
Copyright (C) 1999 JUKI CORPORATION.
All rights reserved throughout the world.

−1−
1. SPECIFICATIONS
1) Max. sewing speed : 2,500 rpm (sewing pitch : 3.4 mm or less)
2) Hook : Horizontal semi-rotary hook (oil wick lubrication)
3) Bobbin : 1.8 fold hook
4) Thread take-up : Link thread take-up
5) Needle : DPx17 #19 to #21
For domestic : DPx17 #19
For export : DPx17 #21
6) Range of thread specification : Cotton thread #30 to #50, spun thread #30 to #50
7) Number of stitches : Panel selection method from among 28 stitches,
36 stitches and 42 stitches
( 28 stitches at the time of delivery)
(Max. 64 stitches when external ROM is used.)
8) Replacement of number of stitches : Panel selection method
9) Number of bartacking patterns stored in memory : Standard number of patterns : 9 patterns
(Max. 99 patterns when external ROM is used.)
10) Needle bar stroke : 45.7 mm
11) Stitch adjustment method : Panel input method
12) Bartacking width : 1.0 mm to 3.0 mm (2.3 mm at the time of delivery)
13) Bartacking length : 7.0 mm to 22.0 mm (10.0 mm at the time of
delivery)
14) Needle entry
15) Thread trimming method : Knife method (Hook on this side : Air cylinder drive
method)
Knifemethod (Hookon rear side : Electromagnetic
valve solenoid drive method)
16) Lift of cloth presser foot : 21 mm (from top surface of cloth presser lower
plate to bottom surface of cloth presser)
17) Cloth feed method : Intermittent feed (2-shaft drive by stepping motor)
18) Sewing machine drive method : DD • AC servomotor (450W) mounted onto
machine head
19) Thread presser drive method : Air cylinder drive
20) Cloth presser drive method : Air cylinder drive
21) Wiper drive method : Air cylinder drive
22) Sewing machine lubrication method : Manual oiling (centralized oil-wick lubrication)
23) Lubricating oil : New Defrix Oil No. 2
24) Center distance of needle adjustment method : Needle portion : manual moving method
Hook portion : stepping motor drive moving
method
(in 0.01 mm steps)
25) Length of center distance of bartacking : 40. 0 mm to 70.0 mm
(57.15 mm (2 and 1/4") at the time of delivery)
26) Loop width : 9 mm to 20 mm (12 mm at the time of delivery)
27) Allowance of loop folding : 11 mm (excluding cross cut section)
28) Allowance of loop presser : 4 mm
28
1
36
11
42
28 stitches 36 stitches 42 stitches

−2−
29) Loop cut method : Selection of cross cut and straight cut
(Range : 9 mm to 20 mm)
(Cross cut at the time of delivery)
30) Loop cut : Cutting method by engaging moving knife with
counter knife
31) Loop bending : Fork folding method
32) Loop supply drive method : Front and rear assisted drive method (stepping
motor)
33) Loop length setting : Automatic recognition method
34) Loop splice detection : Potentiometer automatic splice detection method
35) Bobbin thread winder device : Single and separated drive
36) Temporary stop function : Possible to stop the machine during sewing
37) Bobbin thread counter : Selection method of UP/DOWN counter
(Front and rear hooks can be separately set.
Device automatically stops at COUNT UP.)
38) Fork drive method : AC servomotor (120W)
39) Loosing loop mechanism : Optional
40) Loop pull-out mechanism : Optional
41) Needle thread breakage detector : Optional
42) Needle cooler : Optional
43) Air gun : Optional
44) Table height : Provided with adjustable stand function (Manual
type)
920 mm to 1,250 mm (from floor level to top
surface of throat plate)
45) Dimensions : Width : 1,200 mm
Length : 800 mm
Height : 1,350 mm (excluding thread
stand) (When table comes down to the lowest.)
46) Gross weight : 2,250N (230 kgf)
47) Power consumption : 350VA
48) Operating temperature range : 5 ℃to 35 ℃
49) Operating humidity range : 35% to 80% (no dew condensation)
50) Line voltage : AC200V, 220V, 230V, 240V, 380V, 400V ±10
%
(Power frequency : 50/60 Hz)
51) Air pressure used : 0.5 MPa (5 kgf/cm2)
52) Air consumption : 52 /min. (N / min)
(Splice processing : 1 cyclle/min, excluding
optional)

−3−
2. NAMES AND FUNCTIONS OF COMPONENTS
[1] Names and functions of the main unit
Temporary stop switch
The switch is used to temporarily stop
the machine operation.
Sewing machine head
The machine head
performs sewing while
making the motor drive
the needles.
Clamp feed device
The device is used to
assist in loop feeding.
Operation box panel <P29>
The panel is used to specify/display/
actuate functions.
Start switch
Start switch used
for starting up the
sewing.
Thread stand
The stand is used to
set needle thread
and the thread to be
supplied to the
bobbin winder.
Control box
Controls the whole
machine.
DIP switches
Used to select
functions.
(Note) 1. The <P 29> appearing in
the text above indicates
that a detailed explanation
for the relevant component
is given on page(s) 29.
Loop feeding
device
The device feeds
out the loop.
(Optional)
A type (standard)
ON : Press the
black button.
OFF : Press the red
button.
Bobbin winder
Used to wind a
bobbin with thread.
Power switch (varies in accordance with destination.)
B type (for high-voltage)
ON : Turn the center grip of the switch clockwise.
OFF : Turn it counterclockwise.
Loop supplying device
Performs a series of loop supplying
procedure.

−4−
[2] Names and functions of operation box panel
Sewing screen
Pattern No.
Number of stitches
Length of bartacking
Width of bartacking
Total counter
1st hook counter and set value
2nd hook counter and set value
Name of switch Function
 Set ready switch This switch is used to perform origin retrieval of the sewing machine and loop
supplying device. The machine is set to the sewing stand-by state. Display
screen moves to sewing screen.
Sewing ready lamp (green) lights up in the sewing stand-by state. When
pressing the set ready switch again, the lamp goes out and the setting screen
appears.
Caution : A hazardous state arises when this switch is turned ON,
since the belt loop supplying device operates at a high
speed. Keep your hands or any other part of your body away
from the area of loop supplying device drive and under the
presser foot of the machine.
Set-back switch
Counter key
a. This switch is used to re-set a belt loop at the stand-by position.
Caution : A hazardous state arises when this switch is turned ON,
since the belt loop supplying device operates at a high
speed. Keep your hands or any other part of your body away
from the area of the belt loop supplying device drive and
under the presser foot of the machine.
b. When selecting step operation, this switch acts as the step-feed switch.
This key is used to enter the counter setting screen.
(Refer to page 33 of the Instruction Manual.)

−5−
a. This key is used to enter the setting screen.
b. When changing the sewing data, keep pressing this key for 10 seconds
to release data-lock, In addition, data is locked when keeping pressing
this key again.
These keys are used when inputting various nemeric data.
Presser foot of the machine comes down and the threading is
facilitated.
Caution : A hazardous state arises when this switch is turned ON,
since the belt loop supplying device operates at a high
speed. Keep your hands or any other part of your body
away from the area of the belt loop supplying device
drive and under the presser foot of the machine.
This switch is used when replacing bobbin.
Center-to-center distance between 1st hook and 2nd hook can be
widened to the maximum.
Caution : A hazardous state arises when this switch is turned
ON, since the belt loop supplying device operates at a
high speed. Keep your hands or any other part of your
body away from the area of the belt loop supplying
device drive and under the presser foot of the
machine.
Screen returns from the alarm display screen or the like to the standard screen.
The following functions are performed.
1. Release of the alarm
(When the alarm screen is displayed.)
2. Reset of the sewing counter
(When the counter screen is displayed.)
(When the count up screen is displayed.)
3. Reset of the total counter
(When the counter screen is displayed.)
4. End of the machine adjustment screen
5. End of the check program
This switch is used to temporarily stop the operation or stop the
operation.
Caution : Re-start cannot be performed when the temporary stop
switch is operated during the operation.
a. This key scrolls setting item to the left when displaying setting
screen or the like.
b. This key performs presser foot jump feed operation (traveling
backward) when displaying the sewing screen.
(Refer to page 36 of the Instruction Manual.)
This key selects setting item.
a. This key scrolls setting item to the right when displaying setting
screen or the like.
b. This key performs presser foot jump feed operation (traveling
forward) when displaying the sewing screen.
(Refer to page 36 of the Instruction Manual.)
This screen performs various displays.
These switches change over various settings.
(Refer to page 50 of the Instruction Manual.)
Green color
Standard screen key
Ten key
Needle threading switch
Bobbin replacement switch
Reset switch
Temporary stop switch
Left cursor key
Screen change-over key
Right cursor key
Display screen
DIP switches
Set ready LED switch

−6−
3. TIMING CHART
This diagram gives a basic timing chart. It has to be noted that the operation may vary if an alarm occurs or
input from any of switches and sensors is made.
(Caution) For the basic operation flow, refer to page 25 of the Instruction Manual.
Standard operating timing chart
Start SW Machine rotation Machine stop Start SW
• Fork up/down
(Cam)
• Fork moving
(Servo motor)
• Fork rotation
• Clamp feed
(Stepping motor)
• Loop clamp
• Loop receiver
• Loop presser
• Cutter up/down
• Cutter rotation
• Wiper
• Presser foot of machine
• Machine rotation
Up
Down
Forward end
Wait position
Loop insertion
Backward end
Wind
Release
Forward
Backward
Backward end
Release
Clamp
Up
Down
Up
Down
Up
Down
Rotation
Stop
Forward
Backward
Up
Down
Rotation
Stop

−7−
Standard Adjustment
0.5 mm
2.5 mm
0
-1
4. STANDARD ADJUSTMENT
[1] Machine head components
(1) Adjustment of the main shaft components
1) Removing the play of main shaft
2) Installing the main shaft coupling
Machine arm
Main shaft
Main shaft bushing, middle
Thrust collar
Thread trimmer cam
Main shaft
Machine arm
Main shaft rear bearing
Rubber ring
Flat section
Screw No. 1
Coupling
Servo motor

−8−
Adjustment Procedures Results of Improper Adjustment
○Pulling the thread trimmer cam in the direction of the arrow
mark, lightly press the thrust collar to the main shaft
bushing, middle to fit the thrust collar.
①Provide a clearance of 0.5 mm between the servo motor
and the coupling, and fit the screw No. 1 to the flat section
to install the coupling.
②Insert the rubber ring (R0154240100) in between the main
shaft rear bearing and the coupling, provide a clearance
of 2.5 mm between them, and fit the screw No. 1 to the
flat section to install the coupling.
③Be sure to align the positions of the two screws in the
direction of rotation when making the respective couplings
engage with each other.
○If the phase of the coupling is
improper, the main shaft does
not stop at the normal angle.
○If the coupling installing
clearance is larger than the
specified value, moving gap of
the coupling in the axial direction
is lost. As a result, main shaft
torque will occur.

−9−
3) Adjusting the main shaft sensor
4) Stretching the timing belt (Main shaft-to-hook driving shaft for the front side timing)
Standard Adjustment
Sensor
Main shaft
Pass the center.
Sensor installing base
Sensor
Slit plate
Coupling
Idler pulley
AA

−10 −
Adjustment Procedures Results of Improper Adjustment
○Adjust so that the slit plate passes almost the center of
the sensor and there is no interference, then tighten
setscrew .
1) Bring the needle bar to the lowest position of its stroke.
2) Loosen the idler pulley and loosen the timing belt.
3) Adjust the setscrews in connecting collar at the lowest
position of the needle bar as shown in the figure on the
left.
4) Stretch the timing belt with the idler pulley and check the
position of the setscrews. (The position becomes as form
A.)
(Caution) The position of the screw may be shifted when
stretching the belt. Stretch the belt again since
the crest of the belt is shifted by one.
Timing with the hook on the rear
side is improper and stitch skipping
or defective thread pulling will result.

−11 −
Standard Adjustment
1 kgf 4 mm
5) Adjusting the idler
(2) Adjusting the hook driving shaft components
1) Adjusting the longitudinal position of the oscillator
Oscillator
Hook driving shaft gear
Thrust collar
Face A

−12 −
Adjustment Procedures Results of Improper Adjustment
①Loosen setscrews and adjust the idler.
②Using the belt tension as the standard, adjust the tension
so that the belt sags 4 mm when the center of the belt is
applied with a 1 kgf load.
①Loosen setscrews and .
②When turning the main shaft several times, the oscillator
moves in the direction of the arrow mark and naturally
moves to the position where there is no load.
③Temporarily tighten setscrew .
④Make the thrust collar come in contact with face A on the
machine bed and tighten setscrew .
If the timing belt is excessiuely
pressed, main shaft torque is
increased.
As a result, heat is produced or
worn-out of bearing is advanced, or
belt is damaged early.
○If the longitudinal position of the
oscillator is improper, seizure of
the oscillator or main shaft crank
will result.

−13 −
Standard Adjustment
2) Adjusting the backlash of the oscillator gear
3) Removing the play of the hook driving shaft
Thrust collar (small)
0.1 mm or less
Face A
Thrust collar (large)