SunStar KM-1070 SERIES, KM-1072 SERIES User Manual

USER S MANUAL

KM-1070 SERIES

1-Needle, Unison Feed
Lock Stitch M/C

KM-1072 SERIES

2-Needle, Unison Feed
Lock Stitch M/C

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Best Quality

Best Price

Best Service

SunStar CO., LTD.

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1.

Thank you for purchasing our product. Based on the rich expertise and
experience accumulated in industrial sewing machine production, SUNSTAR
will manufacture industrial sewing machines, which deliver more diverse
functions, high performance, powerful operation, enhanced durability, and
more sophisticated design to meet a number of user’s needs.

2. Please read this user’s manual thoroughly before using the machine. Make
sure to properly use the machine to enjoy its full performance.

3. The specifications of the machine are subject to change, aimed to enhance
product performance, without prior notice.

4.

This product is designed, manufactured, and sold as an industrial sewing
machine. It should not be used for other than industrial purpose.

4

Contents

1. Machine safety regulations --------------------------------------------------------------------- 6

1-1) Transporting machine --------------------------------------------------------------------------- 6
1-2) Installing machine --------------------------------------------------------------------------------- 6
1-3) Repairing machine -------------------------------------------------------------------------------- 6
1-4) Operating machine ------------------------------------------------------------------------------- 7
1-5) Safety devices ------------------------------------------------------------------------------------- 7
1-6) Caution mark position ---------------------------------------------------------------------------- 8
1-7) Contents of marks -------------------------------------------------------------------------------- 8

2. Names of main parts ------------------------------------------------------------------------------- 9

3. Specifications

--------------------------------------------------------------------------------------- 10

4. Installation

--------------------------------------------------------------------------------------------- 11

4.1) Installation place --------------------------------------------------------------------------------- 11

4.2) Machine delivery --------------------------------------------------------------------------------- 11

4.3) Bending the machine backwards ----------------------------------------------------------- 11

4.4) Table drawing ------------------------------------------------------------------------------------ 12

4.5) Installation of Sewing Machine Body ------------------------------------------------------- 13

4.6) Supplying oil -------------------------------------------------------------------------------------- 18

4.7) Trial run (Pedal operation) -------------------------------------------------------------------- 19

4.8) Machine Stop Position Check ---------------------------------------------------------------- 19

4.9) Back tack button (thread trimming type) -------------------------------------------------- 20

4.10) Functional description of function switches --------------------------------------------- 20

4.11) Adjusting Parameter of Sub Thread Adjusting Device ------------------------------- 21

4.12) How to Use Dual Tension ------------------------------------------------------------------- 21

5. Preparations for sewing ------------------------------------------------------------------------ 23

5.1) Installing needle --------------------------------------------------------------------------------- 23

5.2) Bobbin Insertion and Removal --------------------------------------------------------------- 23

5.3) Winding lower thread --------------------------------------------------------------------------- 24

5.4) Inserting upper thread -------------------------------------------------------------------------- 24

6. Sewing -------------------------------------------------------------------------------------------------- 25

6.1) Sewing --------------------------------------------------------------------------------------------- 25

6.2) Adjusting thread tension ----------------------------------------------------------------------- 25

6.3) Adjusting upper thread length after trimming -------------------------------------------- 27

6.4) Adjustment of the stitch length --------------------------------------------------------------- 28

6.5) Adjustment of Presser Foot Lift -------------------------------------------------------------- 28

5

6.6) Adjustment of Presser Foot Pressure ------------------------------------------------------ 29

7. Inspecting and checking ---------------------------------------------------------------------- 30

7.1) Daily Cleaning ------------------------------------------------------------------------------------ 30

8. Maintenance and repair ------------------------------------------------------------------------- 32

8.1) Adjustment of Thread Take-up Lever Spring -------------------------------------------- 32

8.2) Adjustment of Thread Guide on Thread Adjusting Device --------------------------- 33

8.3) Adjustment of Feed Dog Position ----------------------------------------------------------- 33

8.4) Height adjustment of feed dog --------------------------------------------------------------- 34

8.5) Adjustment of feed lift shaft cam and lower feed cam -------------------------------- 34

8.6) Needle and Hook Timing ---------------------------------------------------------------------- 35

8.7) Clearance adjustment of hook and opener ----------------------------------------------- 36

8.8) Lubrication adjustment of hook -------------------------------------------------------------- 36

8.9) Adjustment of Presser Foot Height --------------------------------------------------------- 36

8.10) Timing adjustment of the main auxiliary presser foot and needle -------------- 37

8.11) Trimmer ------------------------------------------------------------------------------------------ 38

8.12) Safety Clutch ------------------------------------------------------------------------------------ 40

9. Causes of troubles and troubleshooting ----------------------------------------------- 41

6

Machine safety regulations

Safety instructions on this manual are defined as Danger, Warning and Notice.
If you do not follow the instructoins, physical injuries and machine damages might be occurred.

:

This indication should be observed definitely. If not, there will be a danger during the installation,
conveyance and maintenance of the machine.

:

When you follow this indication, injuries from the machine can be prevented.

:

When you follow this indication, error on the machine can be prevented.

Caution

Warning

Danger

1-1) Transporting

machine

Danger

1-2) Installing

machine

Warning

1-3) Repairing

machine

Caution

Those in charge of transporting the machine should have a full understanding of the
machine. The following indications should be followed when the machine is being
transported.

More than 2 people must transport the machine.
To prevent accidents from occurring during transportation, wipe off the oil on the
machine compeletely.

The machine may not work properly or breakdown, if installed in certain places, Install
the machine where the following qualifications agree.

Remove the package and wrappings from the top. Take special notice on the nails
on the wooden boxes.
Dust and moisture stains and rusts the machine. Install an airconditioner and clean
the machine regularly.
Keep the machine out of the sun.
Leave sufficient space of more than 50cm behind, and on the right and left side of
the machine for repairing.

EXPLOSION HAZARDS

Do not operate in explosive atmospheres. To avoid explosion, do not operate this
machine in an explosive atomsphere including a place where large quantities of
aerosol spray product are being used or where oxygen is being administered unless
it has been specifically certified for such operation.

[Refer] Details for machine installation are described in 4. Installation.

When the machine needs to be repaired, only the assigned troubleshooting engineer
educated at the company should take charge.

Before cleaning or repairing the machine, turn off the main power and wait 4
minutes till the machine is completely out of power.

Not any of the machine specifications or parts should be changed without consulting

the company. Such changes may make the operation dangerous.
Spare parts produced by the company should only be used for
replacements.
Put all the safety covers back on the machine after the machine has been repaired.

7

KM-1070/KM-1072 Series were designed as industrial sewing machines to perform
sewing on fabric, leather, and other similar materials. Please observe the following
instructions during machine operation.

Read through this manual carefully and completely before operating the machine.
Wear proper clothes for work.
Keep hands or other parts of the body away from the machine’s operation parts
(needle, shuttle, thread take-up lever, pulley, etc.) when the machine is operating.
Keep the covers and finger guard on the machine during operation.
Be sure to connect the earthing conductor.
Turn off the main power and check if the switch is turned off before opening
electric boxes such as the control box.
Stop the machine before threading the needle or checking after work.
Do not step on the pedal when turning the power on.
If possible, install the machine away from source of strong electrical noise such as
high frequency welding machines

1-4) Operating

machine

Warning

Caution

[ Warning ]
Keep motor cover in place before operating, turn off power before inspecting or
adjusting.

1-5) Safety

devices

Safety label : It describes cautions during the machine operation.
Thread take-up cover : It prevents any contact between body and take-up lever.
Belt cover : A device intended to avoid potential risks of getting hands, feet or
clothes jammed by the belt
Label for specification of power : It describes cautions for safety to protect electric
shock during the motors’ rotation. (Voltage input / use Hz)
Finger guard : It prevent contacts between finger and needle.

8

Caution

1)

3)

2)

1-7) Contents of

marks

Warning

Caution mark is attached on the machine for safety.
When you operate the machine, follow the directions on the mark.

1-6) Caution mark

position

9

Names of main parts

① Presser Foot ② Reverse Button
③ Function Switches ④ Oil Window
⑤ Climb Dial ⑥ Thread Winder
⑦ Thread Stand ⑧ Pulley
⑨ Stitch Length Dial ⑩ OP Unit and Panel
⑪ LED Lamp SMPS ⑫ Control Box
⑬ Oil Fan ⑭ Lap Switch

⑮ LED Lamp

Safety Devices

⒃ Thread Take-up Lever Cover ⒔ Finger Guard

Belt Cover

[Fig. 2-1]

Usage

Lubrication method

Max. sewing speed [spm]

Needle in use

Gauge [mm]

Max. stitch length [mm]
Needle bar stroke [mm]

Thread take-up lever stroke [mm]

Manual [mm]
Automatic [mm]

Hook

Sewing space [mm]

Bed size [mm]

Main motor

Manual backtack lever

Automatic backtack device

Automatic trimmer

Automatic presser foot lift device

10

Specifications

Machine Type

Code

Medium and heavy materials

Super heavy materials

None

H

Sewing materials

KM-1070BLX

KM-1070BLX-7

KM-1072BLX

KM-1072BLX-7

KM-1070BLXH(-7)

KM-1072BLXH

Model name

Specifications

For medium/heavy materials For super heavy materials

3.2~12

- 6~12

-

Automatic lubrication type

12
34

82.8
10
16

Horizontal large hook (2.5x)

335

603 × 178

Servo motor (750W)

Basic specifications Basic specifications Basic specifications Basic specifications Basic specifications Basic specifications

- Basic specifications - Basic specifications Basic specifications Basic specifications

- Basic specifications - Basic specifications Basic specifications -

Basic specifications Basic specifications Basic specifications Basic specifications Basic specifications Basic specifications

3,500(P=1~7mm)

2,000(P=8~12mm)

DP×35 (#12∼#23)

134~35 (Nm80~160)

DP×35 (#22∼#25)

134~35 (Nm140~200)

2,800(P=1~7mm)

1,600(P=8~12mm)

2,000(P=1~7mm)

1,600(P=8~12mm)

Presser Foot life

※The speed is varied depending on stitch length. ※Equal to commercial rpm.

Code

1 Needle
2 Needle

0
2

Needle

Code

Non-trimming

Trimming

None

7

Trimming

KM-1070BLX/KM-1070BLX-7 KM-1072BLX/KM-1072BLX-7 KM-1070BLXH/KM-1072BLXH-7

KM-1072BLXH

Max. sewing speed [SPM]

Presser foot overlap

3,500(3,000)
3,200 3,000
2,900 2,800

2,600
2,400
2,200
2,000

2,800 2,000
2,600 1,900
2,400 1,800

2,20 1,750
2,000 1,700
1,800 1,650
1,600 1,600

2.5 or below

2.5~3.0

3.0~3.5

3.5~4.0

4.0~4.5

4.5~5.0

5.0 or above

KM-1070BLX/KM-1070BLX-7 KM-1072BLX/KM-1072BLX-7

Max. sewing speed [SPM]

KM-1070BLXH/KM-1072BLXH-7

KM-1072BLXH

Stitch length [mm]

Presser foot overlap-based control

2,000 1,600

7.0 or below

8.0 or above

11

Installation

4.1) Installation place

1) Do not install the machine near television, radio or
telephone; or the operation of machine can be
interfered with by the noise from the appliances.

2) Connect the ground (earth) wire. An unstable
connection may result in malfunction

4.2) Machine delivery

1) There should be two people to move the machine, as
in the Figure.

4.3) Bending the machine backwards

1) Bend the machine backwards with two hands
grabbing upper part of the body. Make sure to press
the lower part of the board leg of the machine, or the
whole body of machine falls backwards, leading to
physical injuries.

[Fig. 4-1]

[Fig. 4-2]

[Fig. 4-3]

Only trained technicians should install and wire up the machine.
The machine weighs over 50 kg. More than two persons should install the machine.
Do not plug in the machine until installation is completed.
If the operator mistakenly steps down on the pedal with the plug in, the machine will start
automatically and can cause physical injuries.
Use both hands when bending the machine backwards or returning it to the original position. Using
only one hand can lead to severe hand injuries due to the weight of the machine.

Caution

12

4.4) Table drawing

Please use the table provided by Sunstar. When using self-made table , the thick of table should be more than 40mm. Please use table strong enough to sustain

the weight of the machine.

[Fig. 4-4]

13

4.5) Installation of Sewing Machine Body

4.5.1) Hinge and Bed Supporting Rubber

Fix the hinge rubber ① (2EA) and the bed
supporting rubber ② (4EA) at the grooves on the
table using nails ③.

4.5.2) Presser Foot Lift Cylinder Bracket

Fix the presser foot lift cylinder bracket① under the
table② as in the figure using the M8 hexagonal bolt
③.

4.5.3) Oil Fan

Find the oil fan ① in the accessory box and attach it
aligned with the presser foot lift cylinder bracket ②
using screws.

[Fig. 4-5]

[Fig. 4-6]

[Fig. 4-7]

14

4.5.4) Lap Switch

Attach the lap switch ① beneath the table ②
considering the user’s working position with screws.

4.5.5) OP Panel

Fix the operating panel① to the bracket② using a
bolt③ and then fix it to the upper part of the rear arm
using a bolt④.
(Optional：Fix the OP bracket⑤ to the table face
using a tapping screw⑥.)

4.5.6) Control Box and LED Lamp SMPS

Attach the control box① and the LED lamp SMPS②
beneath the right side of the table③ using screws
and fix them at the places as in the figure.

[Fig. 4-8]

[Fig. 4-9]

[Fig. 4-10]

15

4.5.7) Pedal switch and connecting rod

1) Attach pedal switch to pedal switch bracket

with four bolts .

2) As in the Figure, attach pedal switch bracket

to the lower part of table.

3) Connect one end of the connecting rod

with
pedal switch and the other end with pedal, and
then adjust length of the rod.

4.5.9) Adjustment of Belt Tension

Install the motor and sufficiently loosen the fixing
nuts

, . Then due to the weight of the motor ,

tension is generated at the belt

. Fix the fixing nut

in this position and then tightly fasten the fixing

nut

.
Adjust the tension of the belt to make the belt
pressed 10mm when the center is pressed by a finger
as in the figure, and tightly fasten the fixing nut

.

4.5.8) Sewing Machine Body

1) Place the two hinges on the rear bed of the

sewing machine and tightly fasten them using the
screw

.

2) Settle the hinge① on the hinge rubber② of the

table③ and place the sewing machine body on
the bed base rubber⑥.

3) Insert the machine body sustaining pole

into

table

completely. If the pole is not inserted
completely, that may cause accidents because the
pole cannot sustain the weight of machine body
firmly, when the body bent backwards.

4) Install the sewing machine body on the table and
fix the grounding wire

on the hinge using a

screw

.

[Fig. 4-11]

[Fig. 4-12]

[Fig. 4-13]

16

4.5.10) Belt Cover Installation

1) Fix the belt cover on the upper right side of the
arm

and the fixing grooves of the belt cover

using screws .

2) Accurately assemble the belt covers

, and fix

the belt cover

using screws following the same
method. When the assembled belt cover is fixed
to the stud bolt

using screws , the belt cover

installation is complete.

4.5.11) Pneumatic Parts Installation and
Function Check

1)

As in the figure, fix the pneumatic unit

to the
lower part of the table using the wood screw and fix
the regulator to the table T-leg stiffened plate

.

2) Connect the pneumatic tubes according to label
signs and bind the tubes with other lead lines
using the belt clips

.

3) Use the regulator

to set the default pneumatic

pressure at 0.5Mpa.

4) When applying the seam center guide presser
foot, make sure that the pneumatic pressure of the
regualtor

is no highr than 0.3Mpa.

4.5.12) Description of label symbols

Label Sign

Cylinder Function

S1
S2
S3

S4

S5

S6
S7
S8

Backtack
Trimming
Hem height difference

Stitch length conversion

Thread release(Main)

Thread release(Sub)
Presser foot
Seam guide

Add the initial and last backtack sewing function and perform reverse sewing
Perform trimming
When the cylinder is in motion, sewing is performed using the higher

value of the two climb dials attached to the machine.
When the cylinder is in motion, sewing is performed using the lower

value of the two stitch length dials attached to the machine.
It operates when trimming and presser foot automatic lift are

performed to loosen the tension of the upper thread.
Turn on/off the tension of the upper thread using the function switch.
Lift the presser foot 18mm from the needle plate face.
It is used to create sewing lines in parallel along the seam in case of

using two needles.

[Fig. 4-14]

[Fig. 4-15]

However, when the left/right removable thread adjustment device, an optional device is applied, S6
refers to SubL, and S9 refers to SubR.

Note

17

4.5.14) Thread spool stand assembly

Secure the thread spool stand assembly onto the
table using washer

and nut on the right side.

[Fig. 4-16]

4.5.13) Pnematic wiring diagram by model

KM-1070BLX
KM-1072BLX

KM-1072BLXH KM-1072BLX-7(Option)

Button switch
cable

KM-1070BLX-7
KM-1070BLXH-7

KM-1070BLXH

18

[Fig. 4-17] [Fig. 4-19]

[Fig. 4-18] [Fig. 4-20]

1) Lubrication to Bed
Loosen the oil tank entrance screw

and supply oil until the oil gauge reaches the “HIGH” mark . When oil

supply is completed, tightly fasten the screw

. Upon initial installation, run the machine for 30 minutes and

supply oil until the “HIGH” mark.

2) Lubrication to Face Plate
Loosen the two fixing screws for the face plate for disassembly. Supply lubricant through the entrance marked
with an arrow. When oil supply is completed, reassemble the face plate.

3) Lubrication to Hook
Open the sliding plate

and supply oil through the entrance marked with an arrow.

4) Oil Window Check
When oil supply to oiled parts is completed, turn on the power. Operate the sewing machine for five minutes at a
low speed and check for any oil flow in the oil hose which runs through the oil window

on the front part of the
arm. Operate the sewing machine at the speed of 2,000 spm per minute for the first four to five days of operation,
and use the machine at the normal speed afterwards. Then it is able to keep the machine at the best conditions.

4.6) Supplying oil

Operate the machine only after supplying oil when the machine is used for the first time or has been
left unused for a long time.
Only use genuine lubricant of this company. (Lubricant is in the accessory box.)

Caution

Plug in only after oil supply is finished. If the operator mistakenly steps on the pedal with the plug in,
the machine will start automatically and can cause severe injuries.
When handling lubricants, wear protective glasses or gloves to prevent lubricants from contacting
with your eyes or skin. Wash your hands in running water with soap when they are smeared with
lubricant. If lubricant is in the eye, instantly wash it with running water and see a doctor.
Never drink lubricants since they can cause vomiting or diarrhoea. Go to see a doctor, if you
mistakenly drink lubricant.
Keep lubricant away from the reach of children and the youth.

Caution

19

4.8) Machine Stop Position Check

Press the reverse button to make the needle to the highest and lowest position, and check the stop position of the
machine. When the stop position is improper, trimming may be faulty. In this case, the position of the magnetic
holder imbedded in the pulley should be corrected.

4.8.1) Check for up-stop position of needle
bar

The up-stop position of needle bar is where the take­up lever

stops 2mm off of its highest position. For

adjustment, move the magnetic holder

built in a

carved N.U. sign of the pulley to the left and right.

4.8.2) Needle Bar Lower Stop Position Check

The lower stop position of the needle bar is the
position where the punched mark

of the needle

bar meets the end of the needle bar frame

. When
the position is not correct, the position of the
magnetic holders

embedded in the N, D punched
marks of the pulley should be moved left or right for
readjustment.

[Fig. 4-22]

4.7) Trial run (Pedal operation)

1) Press pedal lightly to the position of B to check if the
machine is operating low-speed sewing.

2) Press pedal to the position of C to check if the
machine is operating high-speed sewing.

3) Press pedal backward and forward. And then put the
pedal at neutral position of A to check if needle stops
lower than the upper surface of needle plate.(in case
that needle down stop is set)

4) When pressing pedal to the position of D(or pressing
pedal the position of to D and then replacing pedal
to the position of A), needle will stop higher than the
upper surface of needle plate after trimming.

[Fig. 4-21]

Make sure not to touch or press down parts that are operating or moving during operation. Failure to
follow the safety rules may result in physical injuries or mechanical damages.

Caution

20

4.9)

Back tack button (thread trimming type)

Pressing the back tack button or reverse button during
forward sewing will start reverse sewing immediately .
When you stop the machine and restart it by stepping
down on the pedal with the reverse button

already
pressed down, you can perform reverse sewing from the
beginning. When the machine is in a

stop mode, you
can change up-down position of the needle bar by
pressing the reverse button. Lightly pressing the button
once will stop the needle bar in a high position.
Pressing the reverse button

twice within less than a
second will stop the needle bar in a low position. In
short, the button delivers two functions: one for reverse
sewing and the other for converting vertical position of
the needle.

4.10) Functional description of function switches

1) : Stitch length conversion switch
When the switch is turned on, the lower positioned
dial among the two stitch length setting dials
attached to the machine is applied. When the switch
is turned off, the higher located dial among the two
stitch length dials is applied.

2) : Auto backtack select switch
The switch selects the addition or deletion of the
initial and last backtack sewing function.

3) : Presser bar overlapping change switch
When pressing the switch, the lamp is on. Then the
presser bar overlapping volume is changed to the value
set at the top cover dial B. When pressing it again, the
lamp is off. Then the value set at the top cover dial A
becomes the presser bar overlapping volume.

4) : Supplementary thread tension switch
When the switch is not pressed, the tread tension is
low. When the switch is pressed, the dish is closed,
and the thread tension increases.

5) : Needle bar upper stop switch
Regardless of the machine stop position, the switch sends the needle bar to the highest stop position.

6) : Seam guide operation switch (Exclusive for KM-1072)
The switch is used in case of using two needles. It creates sewing lines in parallel along the seam of the sewing
fabric.

7) : Left auxiliary thread tension switch
When the switch is not in operation, the thread tension is released. When the switch is pressed, the left auxiliary

dish is closed, and the thread tension increases.

8) : Right auxiliary thread tension switch
When the switch is not in operation, the thread tension is released. When the stitch is pressed, the right auxiliary

dish is closed, and the thread tension increases.

[Fig. 4-23]

[Fig. 4-24]

21

4.11) Adjusting Parameter of Sub Thread Adjusting Device

- The default value of A-95 is “0”.

Parameter No. Set Value

Function Name

A-95 0

1

Use the main thread adjusting device①. In order to run the sub thread adjusting
device② while using the main device, press the sub thread tension switch. Then
with the lamp turned on, the dish for the sub thread adjusting device② is closed.
After trimming, the sub thread tension switch is automatically turned off.

In the case where A-95’s parameter is set at “1”, the lamp of the sub thread tension
switch is on, and the sub thread adjusting device ② is running like the main thread
adjusting device①.
In this case, even after trimming, the sub thread tension switch is not automatically
turned off.
In order to release the tension of the sub thread adjusting device②, press the sub
thread tension switch to turn it off.

[Fig. 4-25]

4.12) How to Use Dual Tension

1) Main Thread Adjusting Device

- Adjust tension of the main thread adjusting device① in line with the main sewing material conditions.

- Adjust the main thread adjusting device① and the tension of the lower thread in order to create loops at the
center of the sewing material at even stitch length.

2) Sub Thread Adjusting Device

- The sub thread adjusting device② enables users to easily increase the tension of the upper thread according to
the sewing material height difference and conditions.
For two-needle model, if a dual tension individual operating type (optional) is used, the left and right tension of
the upper thread can be independently adjusted while sewing materials with height difference on the left and
right sides.

- The sub thread adjusting device② should be adjusted in line with the tension of the main thread adjusting
device① and the conditions of sewing materials with height difference.

3) Operating Main·Sub Thread Adjusting Devices

- The main·sub thread adjusting devices①, ② are run by pneumatic pressure. In particular, the sub thread
adjusting device② can be turned on and off easily with functional switches.

- The sub thread adjusting device can be left, right independently run as an optional function. The left, right
function switches can be used to turn on and off the tension.

- During sewing, when the sub thread adjusting device or the left, right sub thread adjusting device in terms of
independently running type is pressed, the lamp is turned on and at the same time the tension of the upper thread
increases. When the button is pressed again, the lamp is turned off, and the tension of the upper thread
decreases.

22

4) Examples of Dual Tension Application
4-1) Basic Specifications

- For the sewing process of handling significant height difference of sewing material, the presser foot°Øs
cross overlap and the tension of the upper thread should be increased to get best sewing quality.

- Turn off the dual tension button C and adjust the tension of the main thread adjusting device according to
the conditions of the main sewing material A.

- Turn on the dual tension button C and adjust the tension of the sub thread adjusting device according to the
conditions of the thick sewing material B.

- Proceed with general sewing work after the dual tension button C is turned off. When the machine reaches
Point B on the sewing material, press the dual tension button C to increase the upper thread tension. When
the sewing for height difference is completed, press the dual tension button C to decrease the upper thread
tension and continue sewing.

4-2) Optional Specifications

- When sewing the materials with different height on left and right sides, the independently
operating (optional) dual tension can be used to get the best sewing quality.

- As in Figure 4-26, when sewing the materials with different height on left and right sides,
upper thread tension should be given differently to the left and right sides to get the best
sewing quality. As such, the sub thread adjusting device should be adjusted as follows:

① Basic specifications: The sub thread adjusting device that supplies upper thread to the thick

part A is reset every time of operation.

② Optional specifications: Turn on the button to operate the sub thread adjusting device that

supplies upper thread to the thick part A between the independently operating function
switch’s dual tension L and R.

- After the sewing with height difference is done, manually adjust the tension of the sub thread
adjusting device to return to default value in case of basic specifications, and press the dual
tension L, R button to reduce the upper thread tension in case of the optional specifications.

[Fig. 4-26]

A

B

C

[Fig. 4-27]

A

23

Preparations for sewing

5.1) Installing needle

5.2.1) Bobbin Removal

Turn the sewing machine pulley to place the
needle above the needle plate.
Open the sliding plate and vertically erect the
flaps holding the bobbin.
Remove the bobbin from the bobbin case using
tweezers.

5.2.2) Bobbin Insertion

Take out the lower thread from the bobbin through
the thread passage

and below the tension spring

plate

, and make the loose lower thread length
50mm.
Bobbin can be inserted in the reverse order of the
bobbin removal.

[Fig. 5-2]

1) Turn the pulley of machine to raise needle bar to its
highest position.

2) Unfasten the fixing screw

.

3) As in the figure

, insert needle straight to the end
with the needle’s long groove facing left and fasten
the fixing screw

firmly.

5.2) Bobbin Insertion and Removal

[Fig. 5-1]

Always turn off the power when mounting a needle.
If the pedal is accidentally stepped, the machine might unexpectedly operate, causing injury.

Caution

Make sure to turn off the power switch when removing the bobbin case.
If the pedal is accidentally stepped, the machine might unexpectedly operate, causing injury.

Caution

24

5.4) Inserting upper thread

1) Place the thread take-up at its the highest position
by turning pulley before inserting the upper thread.

2) The adequate length of upper thread extending from
the needle hole is 50mm.

[Fig. 5-4]

5.3) Winding lower thread

1) Turn on the power switch.

2) Insert bobbin

into bobbin winder shaft .

3) Wind thread on bobbin

several times in the arrow

direction.

4) Push bobbin operating plate

in the direction of

bobbin.

5) Raise presser bar with presser bar lifter.

6) When pressing pedal, the machine starts to operate
and thread winds on bobbin.

7) When thread winding is done, bobbin operating plate

returns automatically.

8) Remove bobbin and cut thread with bobbin winder
knife

.

※ To adjust the amount of bobbin winding, loosen

screw

and adjust bobbin winder adjusting plate

.

[Fig. 5-3]

Make sure not to touch or press down parts that are operating or moving during thread winding.
Failure to follow the safety rules may result in physical injuries or mechanical damages.

Caution

Make sure that thread should be regulated to wind 80% of bobbin capacity.

Caution

Always turn off the power when inserting upper thread.
If the pedal is accidentally stepped, the machine might unexpectedly operate, causing injury.

Caution

25

Sewing

6.1) Sewing

1) Press ON button of power switch .

2) Lamp on the control panel

turns on and machine

is ready to operate.

3) Control sewing conditions by using control panel

.

(See user’s manual of Fortuna IV.)

4) When the button

is pressed to LED On, LED

lamp blinks.

5) Step on the pedal to operate.

[Fig. 6-1]

Wear protective gears for safety. Operation without them may lead to physical injuries.
Turn off the machine in the following situations.
If the operator mistakenly steps on the pedal with the plug in, the machine will start automatically
and can cause severe injuries.

When inserting upper thread
When replacing bobbin or needle
When the machine not in use or the operator leaving the work place.

Caution

6.2) Adjusting thread tension

Sewing Type

Cause Troubleshooting

Good sewing in balance

Upper thread tension is too weak
Lower thread tension is too strong

Upper thread tension is too strong
Lower thread tension is too weak

Make upper thread tension strong or make
lower thread tension weak

Make upper thread tension weak or make
lower thread tension strong

When inserting and removing bobbin case, make sure to turn off the power switch.
If the pedal is accidentally stepped, the machine might unexpectedly operate, causing injury.

Caution

26

6.2.1) Tension adjustment of the lower thread

If you turn screw② on the spring plate① mounted
in hook in a clockwise direction, the lower thread
tension will become stronger and when turned in a
counterclockwise direction, weaker.

①

②

[Fig. 6-2]

6.2.2) Upper arm thread guide

The tension of the upper arm thread guide① should
be set lower than that of the main thread adjusting
devices②. When the nut③ is turned clockwise, the
tension increases. When the nut is turned counter­clockwise, the tension weakens.

[Fig. 6-3]

6.2.3) Main thread adjusting device

1) The tension of the main thread adjusting devices
① should be set at the minimum as possible.

2) Loops should be created at the center of the
sewing material. Make sure that thread break
does not occur on the ultra light material due to
strong thread tension.

3) Adjust the main thread adjusting devices① to
create stitches at regular length. When the nut is
turned clockwise, the tension increases. When the
nut is turned counter-clockwise, the tension
weakens.

[Fig. 6-4]

After the upper arm thread guide is adjusted, the tension of the main thread adjusting devices should
be reset.

Caution

①

②

③

①

27

6.2.4) Supplementary thread adjusting device

1) The supplementary thread adjusting devices①
play a supplementary role in strengthening thread
tension in a prompt manner.

2) The tension of the supplementary thread adjusting
devices① should be set lower than that of the
main thread adjusting devices②. The tension can
be turned on/off with the functional switch.

3) The tension of the supplementary thread adjusting
device gets stronger when it is turned clockwise.
It gets weaker when the device is turned counter­clockwise.

[Fig. 6-5]

6.2.5) Operation of thread adjusting device

The main and supplementary thread adjusting
devices①,② are automatically in operation.
※ When trimming or auto presser bar lift③ is

activated, the tension of the main and
supplementary thread adjusting devices is
released. The supplementary thread adjusting
devices② can be turned on/off with the
functional switch④.

[Fig. 6-6]

[Fig. 6-7]

6.3) Adjusting upper thread length after
trimming

1) During the trimming process, main thread release
tension is not created but only auxiliary thread
release

tension is created.

2) The adequate length of upper thread after trimming
is 50 ~ 60mm.

3) Increasing auxiliary thread release

tension will
make upper thread after trimming short and
decreasing the tension will make it long.

28

6.4) Adjustment of the stitch length

Adjusting dial and designed to control the stitch
length can be set up with two different lengths, and
change the stitch length whenever switch

is pressed

down. After pressing down switch

to turn the switch
on, the sewing machine will carry out sewing at the
stitch length as set on dial

. When pressing down

switch

again to turn the switch off, the machine will

start sewing at the stitch length as set on dial

. Set the

desired stitch length to a carved sign

.

6.5) Adjustment of Presser Foot Lift

The overlap between the main presser foot and the
sub presser foot

could be set at 1~7mm using the

climb dials

, which adjust the presser foot lift. Place

the desired numbers of the climb dials

, at the

punched mark

, and the main presser foot and the

sub presser foot

overlap according to the set value. In
addition, during the sewing process when the hem
height difference is high, the lap switch

can be used.

When the lap switch is pressed, the set value at the dial

becomes the overlap value of the presser feet. When
the lap switch is pressed once again, the overlap value is
converted back into the value of the dial

.

[Fig. 6-8]

[Fig. 6-9]

The value set on the stitch length dial should always be smaller than that of dial . Nonetheless, if
you force turning the dial to set the value of dial to be greater than that of dial , the machine can
be severely damaged.
The function of the stitch length dial is available only for trimming type machines. Stitch length dial

is installed for non-trimming types.

Caution

The value of the climb dial should be bigger than that of the climb dial all the time. If the dial is
adjusted to have a lower value than the dial , it may cause damage to the machine.

Caution

29

[Fig. 6-10]

6.6) Adjustment of Presser Foot Pressure

6.6.1) Presser Foot Pressure

1) Adjust the presser foot pressure to remain weak if
possible (to the extent that the sewing fabric is
slipped away)

2) Turn the pressure adjusting dial① to adjust the
presser foot pressure.

3) When the dial is turned clockwise, the pressure
gets stronger. Otherwise, the pressure gets
weaker.

Stitch Type

Cause Solution

Balanced good stitch

Stitch skipped, inconsistent stitch length

Puckering

Increase pressure

Decrease pressure

Inspecting and checking

30

7.1) Daily Cleaning

7.1.1) Cleaning

1) Open the sliding plate and separate the bobbin
from the hook .

2) Remove dust from the hook

using a soft cloth
or brush and check if any damage is caused to the
hook.

3) When cleaning is completed, install the bobbin
into the hook .

[Fig. 7-1]

Turn off the power switch before operation.
Pressing pedal by mistake may operate machine and result in injuries.
When handling lubricants, wear protective glasses or gloves to prevent lubricant from contacting
with your eyes or skin. Wash your hands in running water with soap when they are smeared with
lubricant. If lubricant is in the eye, instantly wash it with running water and see a doctor.
Never drink lubricants since they can cause vomiting or diarrhea. Go to see a doctor, if you
mistakenly drink lubricant.
Keep the oil out of the reach of children. Keep the oil away from heat.
Use both hands when bending the machine backwards or returning it to the original position. Using
only one hand can lead to severe hand injuries due to the weight of the machine.

Caution

To maintain proper performance of machine and use it for a long time, clean machine regularly
according to the following way. Evan when machine is not in use for a long time, clean according to the
following way before using the sewing machine.

Caution

31

7.1.2) Oil Supply

1) Oil Volume Check
Look at the oil window on the bed cover.
When the oil is at the “HIGH” mark

, it
means oil is sufficient.
If oil is below the “LOW” line , supply
more lubricant following the order below.

2) Oil Supply
Use the authentic SunStar lubricant.
(Lubricant can be found in the accessory box).
Loosen the oil supply entrance screw .
Supply lubricant until the oil reaches the
“HIGH” line

on the oil window of the bed
cover. Make sure that lubricant does not
overflow.

[Fig. 7-2]

7.1.3) Checking

1) When needle is deformed or the end of needle is
damaged, change the needle.

2) Check if upper thread is inserted correctly. (Refer
to 5.4 Inserting upper thread)

3) Run trial sewing.

[Fig. 7-3]

1) Make sure that lubricant does not move above the “HIGH” line . If not, lubricant might leak.
When oil supply is completed, tightly fasten the oil tank entrance screw .

2) When the oil tank settles at the table, make sure that it is vertically positioned.
If it leans to one side, oil might leak out.

3) Make sure to place the reflux felt at the groove of the oil fan.
Otherwise, oil cannot be properly inhaled.

Caution

88

Maintenance and repair

32

8.1) Adjustment of Thread Take-up Lever
Spring

1) Loosen the stopper tightening screw① as in the
figure and turn the thread take-up spring stopper②
counterclockwise. Then the operating scope of the
thread take-up lever spring③ becomes narrower.
Otherwise, the operating scope becomes wider.
※ The standard operating scope of the thread take-

up lever is 5~10mm.

2) Adjustment of Thread Take-up Lever Spring Tension
Loosen the thread adjusting device shaft nut① and turn the groove of the thread adjusting device shaft②
clockwise using a screwdriver. Then the tension of the thread take-up spring③ becomes stronger. Otherwise, it
gets weaker.

3) Adjustment of Thread Take-up Lever Spring Operation Timing
Loosen the stopper screw④ and turn the thread take-up spring guide⑤ clockwise. Then the thread take-up
spring’s③ operation timing gets faster. Otherwise, the operation timing gets slower.
※ The operation timing of the thread take-up lever spring is standard when the stopper screw④ is at the center of

the guide plate⑤.

[Fig. 8-1]

[Fig. 8-2] [Fig. 8-3]

•For machine maintenance and repair, consult with qualified technicians.

•For electrical maintenance and repair, consult with qualified technicians or agencies.

•When safety devices are disassembled, make sure to return them to original positions.

•Use both hands when bending the machine backwards or returning it to the original position. Using

only one hand can lead to severe hand injuries due to the weight of the machine.

•Turn off the switch and pull the plug. Pressing pedal by mistake may result in physical injuries.

- Inspection, maintenance, repair

- Exchanging expendable parts such as needle, hook, knife.

- Adjusting hook oil flow

•In case you operate the machine when the power is on, please take special precaution.

Caution

①

③

②

①

②

④

⑤

③

33

8.2) Adjustment of Thread Guide on
Thread Adjusting Device

When the two tightening screws are at the center of
the thread guide

on the thread adjusting device, this

is a standard position.

1) Loosen the tightening screw

and move the thread

guide

on the thread adjusting device left or right.

2)

For heavy material sewing, move the thread guide
on the thread adjusting device to the left (The thread
length held by the thread take-up lever increases).

3) For light material sewing, move the thread guide
on the thread adjusting device to the right (The
thread length held by the thread take-up lever
decreases).

8.3) Adjustment of Feed Dog Position.

8.3.1) Feed Dog Position When Stitch Length is 0

When stitch length is 0, the feed dog's feed is 0. In
this case, if the feed dog's feed is not 0, please
perform the follow setting.

1) Open the bed cover.

2) Loosen the horizontal crank fixing screw

and
turn the upper shaft pulley. Check if the switch
connection rod

moves, when the upper shaft

pulley is turned.

3) When the switch connection rod

moves, loosen

the switch connection crank fixing screw

and
adjust the angle of the switch by using the angle
adjusting hole of the switch

.

4) When the upper shaft pulley is turned and the
switch connection rod does not move, completely
fix all fixing screws.

8.3.2) Feed Dog Position on Needle Plate

When the stitch length is maximum, the feed dog
position

in the needle plate hole should be
identical from the front (A) and back (B) on the
needle plate. The minimum figure is 0.7mm. If they
are not identical, please perform the follow setting.

1) Loosen the fixing screw

for the feed dog

supporting crank

.

2) Adjust the feed dog base

to set the distances of
(A) and (B). Completely fix the fixing screw
for the feed dog supporting crank.

3) If (A) and (B) are not identical, loosen the fixing
screw

for the feed list shaft crank to adjust the
location. When adjustment is completed, tightly
fasten the fixing screw

.

[Fig. 8-4]

[Fig. 8-6]

1) In the case of wrong feed adjustment, stitch length could be different when moving forward and
backward.

2) Fix the changer with the changer guide pin . Given that the strong fixing would disturb the
movement of the changer, make sure to fix the changer to the extent that it does not move in the
arrow(X) direction.

Caution

[Fig. 8-5]

34

8.4) Height adjustment of feed dog

Set the stitch count at the minimum and place the feed
dog

at the maximum height. The normal condition is

that the feed dog

is located 0.5mm above the needle

plate

. If it is not in the normal condition, take actions

as below to adjust the feed dog height.

1) Turn the upper shaft pulley of the sewing machine to
place the feed dog at the highest position.

2) Lean the sewing machine backward.

3) Slightly loosen the fixing screw for the feed lift shaft
crank

.

4) Turn the feed lift shaft crank

to adjust the feed dog

height to be 0.5mm.

5) When adjustment is completed, tightly fasten the
fixing screw

.

8.5) Adjustment of feed lift shaft cam and
lower feed cam

1) Set the stitch count at maximum and pull down the
needle bar at the lowest point.

2) Make the second fixing screw

of the feed lift shaft

cam

move vertically and tighten the fixing screw.

3) Lift the needle bar to the highest point.

4) Move the first fixing screw

of the lower feed cam

vertically, and tighten the fixing screw.

5) When the adjustment is made as above, the tips of
the needle

and the feed dog contact the face of

the needle plate

.
Otherwise, make adjustment as above following the
above methods.

[Fig. 8-7]

[Fig. 8-8]

When the feed lift shaft crank is turned, make sure that it does not move toward the shaft.

Caution

35

8.6) Needle and Hook Timing

Set the stitch length at minimum and place the needle
at 2mm above the lowest position. Then the hook edge

is positioned at the needle center. The appropriate

distance between the needle groove and the hook edge

is 0.1mm. At this time, the hook edge should not

contact the needle

. If the above conditions are not

met, perform the following adjustments.

8.6.1) Adjustment of Needle and Hook Timing

1) Disassemble the needle plate.

2) Lean the machine backward. Loosen the lower
shaft collar fixing screw

and set the needle

position 2mm above the lowest position.

3) Turn the hook shaft to place the hook edge at the
center of the needle and tightly fasten the fixing
screw

for the lower shaft collar.

8.6.2) Clearance adjustment between needle
and hook

1) Unfasten the fixing screw of the hook base and
control the position of the hook base by turning
the adjusting collar

of the hook base to the left

and right, set the clearance between the hook tip

and needle at around 0.1mm.

2) After control the position tighten the fixing screw

of the hook base.

8.6.3) Adjustment of Hook Needle Guide
Position

The normal condition is that the distance between the
needle

and the needle guide of the hook is

0.1~0.2mm when the needle bar is lifted 2mm from
the lowest point. (When the fixing screw

is turned

clockwise, the needle

gets away from the needle
guide. Otherwise, the needle gets closer to the needle
guide).

[Fig. 8-9]

[Fig. 8-10]

[Fig. 8-11]

When needles are replaced. Check the distance between the needle and the hook.

Caution

36

8.7) Clearance adjustment of hook and
opener

Bring the opener to the hook as close as possible
and loosen the fixing screw

of the opener. Adjust the
opener manually to allow 0.5~0.7 mm of clearance
between the hook stopper

and the groove of the

needle plate

, and tighten the fixing screw of the

opener.

8.9) Adjustment of Presser Foot Height

1) To ensure presser foot s smooth vertical movement,

release the presser foot presser adjusting dial

.

2) Fix the presser foot as lifted by pulling the presser

foot lift lever

and loosen the fixing screw on the

presser foot lift block

.

3) Lift the auxiliary presser foot

10mm above the

needle plate.

4) Place the pin

inserted into the presser bar lift shaft

closely to the presser bar lift bracket and

tighten the fixing screw

while the presser foot lift

lever pulled back

and the presser foot lift block are

closely contacted.

8.8) Lubrication adjustment of hook

8.8.1) Checking the oil supply level of hook

After racing the sewing machine for three minutes,

secure the oil flow checking paper on the right side
of the hook and run the machine at a maximum
speed for ten seconds. (You may use any type of
paper) As shown in the figure, check the oil tape
marked on the paper.

8.8.2) Adjustment of the oil supply level

Make the adjustment when the quantity of oil supply
is not adequate.
a) Take off the sliding plate (left).
b) Turn the machine manually until you see the

adjusting screw

for the oil supply level of the

hook.

c) The amount of the oil supply will decrease when

the adjusting screw

is turned in a clockwise
direction, and increase when turned in a
counterclockwise direction. Check the level of
the oil supply after adjustment.

[Fig. 8-12]

[Fig. 8-13]

Please be noted that the presser bar lifting spring could be separated when the presser foot pressure
adjusting dial is fully released.

Caution

[Fig. 8-14]

37

8.10) Timing adjustment of the main
auxiliary presser foot and needle

8.10.1) Adjustment of maximum ascending
amount of the main

auxiliary presser

foot

The maximum lifting quantity of the main and
auxiliary presser foot is 7 mm. First, set the upper
lid dial at

1 and take out the upper lid. Move the

body

of a climb device towards the arrow

direction until it reaches the stopper plate

. (At this
time, make the surface of the climb shaft cylinder
knuckle

contact the upper cross section of the arm

and then fasten the tightening screw ) Tighten

the crank clamp screw

. After adjustment,

reassemble the upper lid.

8.10.2) Adjustment of lifting amount of the
main

auxiliary presser foot

The height of lifting amount of the main auxiliary
presser foot must be equal. Make the adjustment as
indicated below.

1) Set the presser foot overlap at the maximum.

2) Take out the rubber cap from the upper lid.

3) Loosen the clamp screw

and turn the machine
until the needle tip and the upper part of the feed
dog come to meet on the surface of the needle
plate.

4) As in 2 above, make the main and subordinate
presser feet contact the needle plate at the same
time and after that, tightly fasten the tightening
screw

to finish the adjustment.

5) After adjustment, place back the rubber cap on
the upper lid.

8.10.3) Timing adjustment of the main
auxiliary presser foot and needle

As a standard, the needle tip enters the needle hole of
the feed dog immediately after the main presser foot

touches the feed dog. Likewise, the main presser

foot

comes apart from the feed dog right after the
needle tip comes out of the feed dog. Refer to the
following for adjustments.

1) Disassemble the upper lid with the dial set at

1 .

2) Loosen two fixing screws of vertical movement

cam

of the presser foot.

3) After securing the needle bar in the highest

position, hold the No.1 screw

of the cam so
that it faces up perpendicularly. Afterwards,
tighten the cam-fixing screws.

4) Place back the upper lid after adjustment.

[Fig. 8-15]

[Fig. 8-16]

[Fig. 8-17]

38

8.11) Trimmer

8.11.1) Trimming Order

When the pedal is stepped backward during sewing,
trimming is conducted. The following is the
trimming order.

1) When a trimming signal is entered, as in Figure
(A), the trimming roller lever

is located at the
lowest part of the curved line of the trimmer cam.
In this case, the moving blade

is parted from

the fixed blade

as in Figure (B) and conducts a
rotary movement toward the opener after passing
above the bobbin.

2) As in Figure (C), the trimmer cam conducts the
rotary movement and the trimmer roller lever
contacts the cam. At this moment, the moving
blade

holds the lower and upper threads as in
Figure (D), and performs rotary movement
toward the fixed blade

.

3) When the trimmer roller lever

and the trimmer

cam

's hole are in a line as in Figure (E), the

moving blade

trims the thread by contacting

with the fixed blade

as in Figure (F).

8.11.2) Adjustment of Moving Blade

The moving blade moves the upper and lower
threads to the point of the fixed blade

. At this

time, the moving blade

rotates while it does not
touch the bobbin case, and trimming occurs through
its contact with the fixed blade. Blades can be
adjusted as follows:

1) Loosen the moving blade fixing screw

to the

extent that the moving blade

has the space to

move around.

2) Place the moving blade at the center of the fixed

blade

and the contact area with the moving

blade

, and then tightly fasten the fixing screw .

3) Loosen the collar fixing screw

and loosen the

tightening screw for the trimmer lever

as in

[Fig. 8-18]. .

4) Place the contract area hole

of the moving

blade at the center of the fixed blade

. Make the

collar with the tightening screw

contact the
upper cross-section, and the collar with the
tightening screw

contact the lower cross­section. Fasten the tightening screws above and
the tightening screw of the trimmer lever

as in

[Fig. 8-18].

[Fig. 8-18]

[Fig. 8-19]

39

8.11.3) Fixing Screw and Lower Thread Holder

When the fixed blade is half entered into the
moving blade, trimming is conducted safely at the
lowest possible pressure. At the time of trimming,
the lower thread holder

contacts the moving blade

stably holding the lower thread. Adjustment can

be conducted as follows.

1) Loosen the tightening screw

, and place the

hook base

and the fixing blade base closely.

Fasten the tightening screw

at the hole center.

Loosen the fixing screw

and adjust the distance

between the slide plate guide

and the fixing

blade tip

at some 28mm. After that, tightly

fasten the fixing screw

.

2) Loosen the fixing screws

for the lower thread
holder and properly adjust the lower thread
holder

to make sure that it does not pull the
thread neither too strong nor too week. Then
tightly fasten the fixing screws

.

[Fig. 8-20]

8.11.4) Adjustment of Trimmer Cam and Lever

The location of the trimmer cam is determined by
the movement of the moving blade

. Upon

trimming, the trimming lever roller

contacts the
lowest curved line of the trimmer cam. However,
during sewing, the trimmer lever roller

and the

trimmer cam

do not contact each other. To make it

sure, adjustment can be conducted as follows.

1) Loosen three trimmer cam fixing screws

and

the trimmer lever tightening screw

.

2) While the thread take-up lever is located at the

highest point, adjust the cam to place the center
of the opener shaft

, the center of the trimmer

cam setting hole

and the center of the trimmer

lever roller

at the same line A as in the figure.

3) Tightly fasten three fixing screws

and the

trimmer lever tightening screw

.

4) Loosen the trimmer clamp fixing screw

5) Adjust the trimmer cylinder shaft to make the

moving blade

contact the fixed blade for
trimming when the trimmer cylinder stroke is
maximum.

6) Tightly fasten the fixing screw

.

[Fig. 8-21]

40

8.12) Safety Clutch

The safety device for the lower shaft timing pulley is
to prevent hook damage caused by thread winding
around the hook or the setting disruption.

1) Slightly loosen two piston stopper screw nuts

.

2) When the two piston stopper screws

are turned
clockwise, it increases torque, and vice versa. After
torque adjustment, tightly fasten the nut

.

[Fig. 8-22]

41

Causes of troubles and troubleshooting

Direction and height of
needle

Needle

Ascending level of needle
bar

Height of needle

Gap between needle and
hook

Threading method
Needle
Direction and height of

needle
Upper thread tension
Lower thread tension
Working capacity of take-up

lever spring
Direction and height of

needle
Needle
Threading
Ascending level of needle

bar
Height of needle bar

Gap between needle and
hook

Racing-proof spring of
bobbin case

Take-up lever spring

Needle breaks

Thread breaks

Stitch skips

1

2

3

Needle is inserted into wrong
direction.

Needle is bent.
Bad timing of feed dog.
Bad timing of needle and hook.

Bad timing of needle and hook.

Bad timing of needle and hook.

Wrong threading.
Bent needle or broken needle tip.
Needle inserted in the wrong

position.
Too tight upper thread tension.
Too tight lower thread tension.
Loose upper thread.

Needle inserted in the wrong
position.

Bent needle or broken needle tip.
Thread passing at wrong position.
Wrong timing of needle and hook.

Wrong timing of needle and hook.

Wrong timing of needle and hook.

Remaining length of upper thread
is short .

Due to bobbin racing during
trimming, lower thread dropping
from bobbin case becomes too
short to go up.

Unable to lift lower thread due to
weak take-up lever spring.

Reinsert the needle correctly.

Replace the needle.
Adjust the timing of feed dog.
Adjust the timing of needle and

hook.
Adjust the timing of needle and

hook.
Adjust the timing of needle and

hook.
Thread the needle correctly.
Replace the needle.
Insert the needle correctly.

Reduce tension of upper thread.
Reduce tension of lower thread.
Adjust take-up lever spring.

Reinsert the needle in the right
direction.

Replace the needle.
Replace the needle.
Adjust the timing of needle and

hook.
Adjust the timing of needle and

hook.
Adjust the timing of needle and

hook.
Adjust the thread adjusting

device.
Replace the racing protection

spring.

Adjust the working capacity of
take-up lever spring.

No Symptom Checkpoints Root cause Corrective action

42

Tension of fixed blade

Edge of movable and fixed
blades

Direction of needle
Check the crossing of

trimmer cam notch mark
and blade

Check the Up-stop position
of needle

Upper thread
does not sink.

Lower thread
does not sink.

Trimming errors

Upper thread is
pulled out when
sewing
commences.

4

5

7

6

Too tight upper thread tension.
Too loose lower thread tension.
Too weak upper thread tension.
Too strong lower thread tension.
Tension not aligned between

movable and fixed blades.
Abrasion in blade groove of

movable and fixed blades.
Wrong needle insertion.
Insufficient crossing quantity of

movable and fixed blade.

Too strong upper thread tension.
Too thick a needle for thread.
Take-up lever pulls out the upper

thread because the needle up
and down position is too high.

Reduce tension of upper thread.
Increase tension of lower thread.
Increase upper thread tension.
Decrease tension of lower thread.
Adjust tension of movable and

fixed blade.
Replace movable and fixed

blades.
Reinsert the needle correctly.
Adjust the strokes of movable

and fixed blades.

Adjust tension of upper thread.
Check thickness of needle.
Adjust the up-stop position of

needle.

No Symptom Checkpoints Root cause Corrective action