SunStar KM-380BL User manual

SSUUNNSSTTAARR MMAACCHHIINNEERRYY CCOO..,, LLTTDD..
User’s
Manual
KM-380BL
1 needle, unison feed,
lockstitch cylinder bed type
sewing machine
(with vertical large hook)
KM- 390BL
1 needle, unison feed,
lockstitch cylinder bed type
sewing machine
(with horizontal large hook)
KM-390BL
KM-380BL
1) For proper use of the machine, thoroughly
read this manual before use.
2) Keep this manual in a safe place for future
reference in case the machine breaks
down.
MMMMEE--005500662299

Best Quality
Best Price
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SSUUNNSSTTAARR MMAACCHHIINNEERRYY CCOO..,, LLTTDD..
R
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.

Safety rules for machines .................................................................................................... 4
1. Specification..................................................................................................................... 8
1) Sewing machine .......................................................................................................................................................... 8
2. Installation ........................................................................................................................ 8
1) Confirming oil supply................................................................................................................................................. 9
2) Lubricating each friction part ..................................................................................................................................... 9
3. Machine Adjustment ...................................................................................................... 11
1) Inserting needle ......................................................................................................................................................... 11
2) Inserting lower thread to bobbin............................................................................................................................... 11
3) Adjustment of inserting lower thread....................................................................................................................... 11
4) Inserting lower thread ............................................................................................................................................... 12
5) Routing upper thread................................................................................................................................................. 13
6) Adjusting upper thread tension................................................................................................................................. 13
7) Adjusting presser foot pressure ................................................................................................................................ 14
8) Adjusting forward and reverse stitch length ............................................................................................................ 14
9) Adjusting sub presser foot and upper feed presser foot........................................................................................... 15
10) Adjusting timing of sub presser foot, upper feed presser foot and needle............................................................ 16
11) Adjusting feed dog height....................................................................................................................................... 16
12) Timing of needle plate, needle and feed dog ......................................................................................................... 17
13) Adjusting timing of needle and hook ..................................................................................................................... 18
14) Adjusting clearance between hook and opener ..................................................................................................... 19
15) Assembling feed cam.............................................................................................................................................. 19
16) Adjusting safety assembly...................................................................................................................................... 19
4. Causes of Trouble and Troubleshooting....................................................................... 20
1) Sewing machine troubleshooting ............................................................................................................................. 20
5. Table drawing ................................................................................................................. 22
1) KM-380BL ............................................................................................................................................................... 22
2) KM-380BLB ............................................................................................................................................................ 23
3) KM-390BL ............................................................................................................................................................... 24
Table of Contents

Safety Rules for Machines
Safety labels in the manual are categorized into danger, warning and caution.
Failure to follow the safety rules may result in physical injuries or mechanical damages.
The safety labels and symbols are defined as follows.
[The meaning of the safety labels]
Instructions here shall be observed strictly.
Otherwise, the user will be killed or suffer severe physical injuries.
Instructions here must be observed, or the user could suffer fatal or severe physical
injuries.
Instructions here should be observed, or the user could face physical injuries or
mechanical damages.
Danger
[The meaning of symbols]
This symbol means a must-not.
Warning
Caution
4
This symbol means that an electric shock may be caused if the
instruction is not followed properly.
This symbol means a must for safety.

1-1) Machine
mobilization
Danger
1-2) Machine
Installation
Caution
1-3) Troubleshooting
Danger
If in need of troubleshooting, call a trained A/S engineer who has been educated by
Sunstar.
ⓐBe sure to turn the power off before cleaning and repair. And wait for about 4 minutes until
the machine discharges completely.
ⓑPart of or the entire machine should not be modified without any consultation with our
company. Such modification could threaten the safety in operating the machine.
ⓒIn case of repair, change the damaged part into the genuine part of our company
ⓓAfter repair, cover the machine with the safety cover that was removed for repair.
Only personnel with a full understanding of the safety rules should move the
machine. The following directions must be observed when transferring the machine.
ⓐAt least 2 persons should move the machine together.
ⓑIn case the machine should be transported, wipe the oil covered on the machine to prevent
accidents.
Because physical damages such as the machine’s dysfunction and breakdown are
likely to occur depending on the environment in which the machine is installed, the
following preconditions must be met.
ⓐPlease unpack the machine package in order from the upper side. Be particularly careful
of the nails in the wooden box.
ⓑBecause machines are apt to be contaminated and corroded by dust and moisture, install a
climate controller and clean the machines regularly.
ⓒKeep the machine out of direct rays of the sun.
ⓓKeep both sides and the backside of the machines at least 50cm from the wall to secure
enough space for repair.
ⓔDon’t run the machine near places with any danger of explosion.
Don’t run the machine near places with any danger of explosion, including places where
sprays like aerosol are used in large quantities or oxygen are dealt with, unless the exact
actions concerning the operation are guaranteed to avoid the explosion.
ⓕIlluminators do not come equipped with the machine due to the machine’s characteristics.
So, users should install the lighting apparatus around the working area.
[Note] The details about the installment of the machine are described in “2.
Installation”.
5

6
The KM-380BL/390BL Series are manufactured for industrial use to sew textiles and other
similar material. When running the machine, users should observe the following things.
ⓐRead the manual before operation of the machine to fully understand the details about its
operation.
ⓑDo not forget to wear garment suitable for safe work.
ⓒKeep your hands or any part of the body away from the running part of the machine like the
needle, hook, thread take-up spring, pulley, etc.
ⓓDo not remove any type of cover during operation for safety reasons.
ⓔBe sure to connect the earthed line.
ⓕBefore opening an electric box such as a control box, be sure to shut off the power supply and
make sure that the power switch is set to “OFF”.
ⓖBe sure to stop the machine when threading the needle or before checking after sewing.
ⓗDo not switch on the power supply with the foot on the pedal.
ⓘDo not run the machine when the cooling fan is clogged. Be sure to clean the air filter in the
control box once a week.
ⓙIf possible, keep the machine away from strong electromagnetic fields like areas around a high
frequency welding machine.
1-4) Machine
Operation
Warning
Warning
ⓐSafety Label: Cautions that need to be heeded to during operation.
ⓑThread take-up spring cover: A device to prevent the human body from touching the thread
take-up spring.
ⓒBelt cover: A device to prevent hands, feet and clothing from getting jammed by the belt.
ⓓFinger guard: A device to prevent fingers from contacting the needle.
1-5) Safety Device
Warning
Always start the machine with safety covers in place since
fingers or hands could be injured or cut off by the belt. Turn off
the power switch during check-ups or adjustments.
ⓓ
ⓐ
ⓒ
ⓑ

7
“Caution” is attached to the machine for safety.
In case of starting to run the machine, read the directions of “Cautions” carefully.
1-6) Position of
Caution Mark
1-7) Content of
“Caution”
Caution
CAUTION
경고
Do not operate without finger guard and
safety devices. Before threading, changing
bobbin and needle, cleaning etc. switch off
main switch.
손가락 보호대와 안전장치 없이 작동하지
마십시오.
실, 보빈, 바늘교환시나 청소전에는 반드시
주전원의 스위치를 꺼 주십시오.
CAUTION
경고
Hazardous voltage will cause injury.
Be sure to wait at least 360 seconds before
opening this cover after turn off main switch
and unplug a power cord.
고압 전류에 의해 감전될 수 있으므로 커버를
열 때는 전원을 내리고 전원 플러그를 뽑고
나서 360초간 기다린 후 여십시오.
CAUTION
경고
Do not operate without finger guard
and safety devices. Before threading,
changing bobbin and needle, cleaning
etc. switch off main switch.
손가락 보호대와 안전장치 없이 작동하지
마십시오.
실, 보빈, 바늘교환시나 청소전에는 반드시
주전원의 스위치를 꺼 주십시오.
CAUTION
경고
Hazardous voltage will cause injury.
Be sure to wait at least 360 seconds
before opening this cover after turn
off main switch and unplug a power
cord.
고압 전류에 의해 감전될 수 있으므로 커버를
열 때는 전원을 내리고 전원 플러그를 뽑고
나서 360초간 기다린 후 여십시오.
[Position of Caution Mark]

1) Sewing machine
8
1
Specification
Sewing speed
Stitch length
Needle
Hook
Needle bar stroke
Gap in height between main
and sub presser foot
Presser foot lift
Cylinder diameter
Motor
Model
Specification KM-380BL KM-390BL
Max. 2,200 spm
Max. 6mm
DP 17 18( 11~ 23) DP 17 23( 11~ 23)
Vertical large hook Horizontal large hook
34.2
25.5
By Hand 10mm/By Knee 15mm
50mm 77mm
250W 2P Clutch Motor
2
Installation
Warning
▶Installation of the machine should be performed by a trained engineer.
▶Any electrical wiring must be performed by a qualified technician or agent.
▶The machine weighs over 32kg. At least 2 persons should carry out the installing work.
▶Plug in after the installation is complete.
If the operator mistakenly steps down on the pedal with the pug in, the machine will start
automatically and can cause physical injuries.
▶Connect the ground (earth) wire.
An unstable connection may result in an electric shock or a malfunction.
▶Place the belt cover on top of the machine.
▶Use both hands when bending the machine backwards or returning it to the normal position.
Using only one hand can lead to severe hand injuries due to the weight of the machine.

9
Caution
▶Do not plug in only before 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 avoid contact with your eyes or
skin. Inflammation may be caused otherwise. Never drink lubricants since they can cause
vomiting or diarrhea. Keep out of the reach of children.
▶Operate the machine only after adding oil when the machine is being used for the first time or
has been left unused for a long time.
[Figure 1]
1) Confirming oil supply
A. Confirming oil tank
KM-380BL/390BL
In case of oil tank installed in the upper part of arm, supply
oil to the level of the marked line after opening the cover
. (Refer to Figure 1)
2) Lubricating each friction part
Be sure to supply oil into the oil holes marked red (arrow marks) and the oil holes in the friction parts before operating the machine.
[Figure 2] [Figure 3]

10
[Figure 4] [Figure 5]
[Figure 6] [Figure 7]
[Figure 8]

11
1) Inserting needle
KM-380BL/390BL
As in Figure 9, move the needle upper end so that it directly
touches the upper side of the stopper hole when the groove
of the needle is inserted facing left. Then, use the fixing
screw to fix the position of the needle.
[Figure 9]
3
Machine Adjustment
Caution
▶Always turn off the power when mounting a needle.
If the operator mistakenly steps on the pedal while the power is on, the machine will start
automatically and can result in physical injuries.
▶When using clutch motor, be aware that the motor will continue to rotate for a while even after
the power is switched off due to inertia.
Start to work on the sewing machine only after the motor has come to a complete stop.
2) Inserting lower thread to bobbin
KM-380BL/390BL
a. Pass the thread through the hole from back to front of the
tension adjustment dish .
b. Pull the thread to bobbin and wind it clockwise 5 or 6
times from the lower side.
c. Push the lever so that the pulley touches V-belt and
operate the machine.
d. When the lower thread is winded thoroughly up to the
bobbin, the pulley separates automatically from the V-belt.
(Refer to Figure 10)
3) Adjustment of inserting lower thread
KM-380BL/390BL
a. In case that the lower thread winds up irregularly, loosen the screw and adjust it by moving from side to side and tighten the
screw again.
b. The amount of winded lower thread increases when the adjustment screw turns clockwise and it decreases turns counter
clockwise.
c. Turning the nut clockwise makes the lower thread tension winded to the bobbin stronger and counterclockwise makes it weaker.
[Figure 10]
Caution
▶Turn off the power when adjusting the lower thread tension.
If the operator mistakenly steps down on the pedal while switched on, the machine will start
automatically and can cause physical injuries.
▶When using the clutch motor, be aware that the motor will continue to rotate for a while even
after the power is switched off due to inertia.
Start to work on the sewing machine only after the motor has come to a complete stop.

12
4) Inserting lower thread
KM-380BL
a. Inserting and removing bobbin case (Refer to Figure 11)
- The bobbin case is removed from the hook when you grab and pull the bobbin case handle .
(The bobbin is separated when you release the handle .)
- In case of inserting the bobbin case , grab the handle and insert.
b. Inserting lower thread (Refer to Figure 11)
- Insert the bobbin to the bobbin case . Then, insert the thread to the thread groove and place it under the tension
adjustment plate spring .
c. Adjusting lower thread tension (Refer to Figure 11)
- The lower thread tension becomes stronger by turning the tension adjustment screw clockwise, and it becomes weaker by
turning the screw counter clockwise.
- Adjust the lower thread tension to a degree that the thread get loosened by its own weight when you fall the bobbin case
grabbing the end of the thread.
KM-390BL
a. Removing bobbin
- Place the needle in the highest position, and then like in Figure 12, open the sliding plate and lift the bobbin holder to
remove the bobbin .
b. Inserting lower thread
- Insert the bobbin winded up by thread into the bobbin case . As in Figure 13, pull out the lower thread by passing the
thread through the part of the thread path and under the tension spring plate . Then, Pull the thread end through the gap
between the hook and the opener . The adequate length of the pulled-out lower thread over the sliding plate is 50mm.
c. Adjusting lower thread tension
- Like in Figure 13, turning the tension adjustment screw clockwise makes the lower thread tension winded to the bobbin
stronger and counterclockwise makes it weaker.
[Figure 12] [Figure 13]
About 50 mm
[Figure 11]

13
5) Routing upper thread
KM-380BL/390BL
Place the thread take-up lever to the highest position and hang
the upper thread like in Figure 14.
[Figure 14]
6) Adjusting upper thread tension
KM-380BL/390BL
A. Adjusting the upper thread tension
- Like in Figure 15, turning the tension adjustment nut of the thread tension control assembly clockwise makes the upper
thread tension stronger and counterclockwise makes it weaker.
B. Adjusting the thread take up
a. Adjusting the thread take up stroke
- As in Figure 15, loosen the stopper fastening screw , and turn the thread take up spring stopper counter clockwise to
make the operational scope of the thread take up spring bigger, and clockwise to make it smaller.
Caution
▶Turn off the power switch when routing the upper thread.
If the operator mistakenly presses down on the pedal while switched on, the machine will start
automatically and can cause physical injuries.
▶When using the clutch motor, be aware that the motor will continue to rotate for a while even
after the power is switched off due to inertia.
Start to work on the sewing machine only after the motor has come to a complete stop.
[Figure 15]
good swing
when the upper thread tension is strong
when the upper thread tension is weak

14
7) Adjusting presser foot pressure
KM-380BL/390BL
Turning the tension adjustment screw clockwise will make the
presser foot pressure stronger, and counter clockwise to make it
weaker. (Refer to Figure 16)
8) Adjusting forward and reverse stitch length
KM-380BL/390BL
a. The stitch length adjustment is finished when you coincide
the indication line of the pipe with your desired stitch
length on the gauge using the nut .
b. Turning the nut clockwise makes the stitch length smaller
and counter clockwise makes it bigger.
c. When the reverse stitch length is needed, pull downward the
lever . (Refer to Figure 17)
[Figure 16]
[Figure 17]
Caution
▶After disassembling and adjusting a safety device, always place it back to the original position
and check whether it functions as intended.
▶Use both hands when pushing the machine backward or returning it to the original position.
Due to the weight of the machine, your hand can get stuck in the machine if you should slip.
▶When adjusting the machine with the switch on, be sure to pay extreme caution to the safety.
▶Only trained engineers must perform repair or inspection of the machine.
▶For electrical repair or inspection, always consult with qualified technicians or agent.
b. Adjusting the thread take up spring tension
- As in Figure 15, loosen the shaft screw of the thread adjustment assembly, and insert the driver into the groove of the
thread tension control assembly shaft . Turn clockwise to make the spring tension of the thread take up stronger and
counter clockwise to make it weaker.
c. Adjusting operation timing of the thread take up spring
- As in Figure 15, loosen the stopper screw , and turn the thread take up spring gauge clockwise to make the operation
timing of the thread take up spring faster, and clockwise to make it slower.

15
9) Adjusting sub presser foot and upper feed presser foot
KM-380BL/390BL
It is normal that both auxiliary presser feet and upper feed presser foot more up and down to the same height.
Take the following steps either to adjust the stroke of both to be the same or to make one of the two adjusted lower or higher,
depending on sewing materials.
A. Adjusting the strokes of both to be the same.
a. The vertical running range of the sub presser foot and the upper feed presser foot is from 2 to 5.5 mm.
b. Loosen the nut to adjust vertically in accordance with material’s condition. (Refer to Figure 18)
(Placing the nut to upper position makes the movement bigger, and to lower position to make it smaller.)
c. When adjustment is complete, make sure the timing adjustment state explained in the article 10 of page 16.
a. Adjusting the sub presser foot
- Loosen the presser bar pressure adjustment screw in Figure 16 on page 14 and the bracket fixing screw in Figure 19.
- Adjust vertically the bracket fixing screw so that the sub presser foot goes up by 10mm from the upper side of the
needle plate when the presser bar lifter is up.
- When the adjustment is finished, fix tightly the bracket fixing screw and adjust adequately the pressure adjustment screw.
- After adjusting the sub presser foot height, adjust the upper feed presser foot.
b. Adjusting the upper feed presser foot
- With the presser bar lifter is put, loosen the crank fastening screw and place the needle at the highest point.
- Adjust up and down the upper feed foot presser height in accordance with material.
- When the adjustment is finished, fix tightly the clamp fixing screw , and make sure the timing adjustment state explained
in the article 10 of page 16.
B. In case of adjusting differently the movement of the sub presser foot and the upper feed presser foot
[Figure 18]
[Figure 19]

16
10) Adjusting timing of sub presser foot, upper feed presser foot and needle
KM-380BL/390BL
When the needle goes downward, the upper feed presser foot should already be contacted with the feed dog before the end
of needle touches with the upper side of feed dog . And when the needle goes upward and the end of needle removes
from the upper side of feed dog , the upper feed presser foot should be contacted with the feed dog . In case that these timings
are not coincided, loosen 2 presser foot vertical movement cam fixing screws and adjust from side to side the fixed position of
vertical movement cam . (Refer to Figure 20)
[Figure 20]
<When the needle goes downward > <When the needle goes upward >
11) Adjusting feed dog height
KM-380BL
a. Bend the machine so that its lower side of bed revealed, and
adjust the pulley to place the feed dog at the highest point.
b. Loosen the screw and adjust the height by moving
vertically the feed dog .
(The standard position of the maximum height of the feed
dog is 1mm from the upper side of needle plate.)
c. When the height adjustment is complete, fasten tightly the
screw .
[Figure 21]
KM-390BL
a. Turn the pulley to place the feed dog to the highest point.
As in Figure 22, move up and down the feed dog with the
feed dog fixing screw and the eccentric collar fixing screw
are loosened. The standard position the feed dog is 1mm
from the upper side of needle plate by moving the feed dog
up and down.
b. When the adjustment is complete, fasten tightly the fixing
screw with the eccentric collar is closely contacted with
the lower part of feed dog.
[Figure 22]

17
12) Timing of needle plate, needle and feed dog
KM-380BL
Locating the feed dog and the needle plate
a. Loosen the screw in Figure 23. Adjust the location of the feed dog so that the gap between the feed dog and the needle
plate before and after the movement is same. And adjust the feed dog movement to maximum.
b. After the adjustment, fasten the screw .
Location of the needle hole and the needle on the feed dog
a. While descending the needle bar by turning slowly the pulley, check if the needle is descending toward the center of the
needle hole on the feed dog.
b. If the needle does not descend toward the center of needle hole on the feed dog,
Make sure if the screw in Figure 23 is fastened tightly to the V-groove on the shaft.
After loosening the screw , hold the lower part of the needle bar frame to adjust it to the correct location.
When the adjustment is finished, fasten tightly the screw .
[Figure 23]
KM-390BL
Locating the feed dog and the needle plate
a. Loosen the screw in Figure 24. Adjust the location of the feed dog so that the gap between the feed dog and the needle
plate before and after the movement is same. And adjust the feed dog movement to maximum.
b. After the adjustment, fasten the screw .
Location of the needle hole and the needle on the feed dog
While descending the needle from its highest point by turning the pulley manually, check if the needle is descending toward the
center of the needle hole on the feed dog. If the needle does not descend toward the center of needle hole on the feed dog, loosen
the screw and hold the lower part of the needle bar frame to adjust it to the correct location. When the adjustment is
finished, fasten tightly the screw .
[Figure 24]

18
Adjusting the timing of the needle and the feed dog
a. Remove the needle and take the timing belt off.
b. Place the thread take up to the highest point by turning the pulley and coincide the arm marked point with the marked
point on the pulley ring by turning the pulley ring .
c. In this state, turn the timing(lower) pulley to adjust the red baseline on the bed to the red baseline of the timing(lower)
pulley. Then, put the timing belt .
d. Check after the adjustment if the end of needle descends and coincides with the upper side of needle plate when the upper
side of feed dog is ascending and coincided with the upper side of needle plate.
[Figure 25]
Highest point of
thread take up
13) Adjusting timing of needle and hook
KM-380BL
a. Place the stitch to “0” and turn the pulley to place the needle
bar to its lowest point. Later, like in Figure 26, ascend the
needle by 2.4mm so that the gap between the upper side of
thread hole of the needle and the hook point is adjusted to
2mm by loosening two fixing screws .
After adjusting the needle and the hook point to be around
0.05~0.1mm by moving the hook from side to side, fasten
tightly two fixing screws .
[Figure 26]
0.05mm~0.1mm
2.4mm
2mm
Hook point
Thread hole
KM-390BL
a. Place the stitch to “0” and turn the pulley to place the needle
bar to its lowest point. Later, like in Figure 27, ascend the
needle by 2.3mm so that the gap between the upper side of
thread hole of the needle and the hook point is adjusted to
2mm by loosening three fixing screws .
b. Loosen the two fixing screws and adjust it from side to
side so that the clearance between the needle and the hook
point to be about 0.05~0.1mm.
c. After the adjustment, make the gearing between the hook
shaft gear and the lower shaft gear to maintain proper
clearance, and fasten tightly the three fixing screws .
[Figure 27]
Hook point
Needle

19
14) Adjusting clearance between hook
and opener
KM-390BL
Loosen the fastening screw and adjust the opener from
side to side so that the clearance between the hook and the
opener to be 0.2mm when the opener is pulled to its
maximum to the direction of arrow as shown in Figure 28.
When the adjustment is finished, fasten tightly the fastening
screw .
[Figure 28]
15) Assembling feed cam
KM-380BL
The standard is when the No. 1 fixing screw of the feed cam
“A”, the center of No. 1 fixing screw of the feed cam “B”,
and the center of the crank rod lubricating hole are being
coincided in one straight line like in Figure 29 after fixing the
needle to its lowest point.
In this state, turn the pulley to raise needle and make the end of
hook and needle cross. After that, feed dog and needle do not
move when moves reverse lever up and down.
[Figure 29]
KM-390BL
The standard is when the No. 2 fixing screw of the feed cam
and the upper shaft marked line are coincided as in Figure 30
after placing the thread take up to its highest point.
[Figure 30]
so only the pulley of safety assembly rotates idly.
In case that the safety assembly starts operating during the
work, turn power switch off and remove causing factors of load.
Later, with safety button pressed, turn the pulley to place the
driving ball of safety assembly to its original position.
Adjust the intensity of the safety assembly spring by
rotating three safety assembly adjustment screws from
side to side in accordance with working conditions.
(Turning the screw to left makes the intensity stronger, and
right to make it weaker. Make sure to give same pressure
on the three screws.)
16) Adjusting safety assembly
KM-390BL
If the load occurs by foreign substances on thread, needle, etc. during the sewing operation, the driving ball of safety assembly in
Figure 30 is removed to prevent damage of the hook and other major parts from the load, and the pulley and the clutch plate
on the safety assembly are removed. Then, the driving force of timing belt on the upper shaft does not delivered to the lower shaft,
[Figure 31]
Feed cam “A” Feed cam “B”

20
4
Causes of Trouble and Troubleshooting
1) Sewing machine troubleshooting
No Symptom Checkpoints Root cause Corrective action
1
2
3
4
5
Needle breaks
Thread breaks
Poor thread
adjustment
Upper thread
falls out when
starting to sew
or sewing is
skipped
Trimming miss
Reinsert the needle correctly and
place closely it to its highest position
Change 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
Change the needle
Insert the needle correctly
Reduce tension of upper thread
Reduce tension of lower thread
Adjust take-up lever spring
Adjust the upper and lower thread
tensions
Adjust the thread take up spring
tension
Adjust the gap between the opener
and hook
Reinsert the needle correctly and
push in to its highest level
Change the needle
Insert the thread in the right way
Adjust the timing of the needle and
the hook
Increase the adjustment volume of
the upper thread on the control box
Adjust the location and tension of the
lower thread holder
Readjust the needle’s up-stop film
position
Readjust the movable knife setting
position
Correct the tension adjustment and
surface contact of movable and fixed
knives
Needle is inserted into wrong position
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 loose lower thread tension
Loose upper thread
Upper and lower thread tensions are
bad
Thread take up spring tension is
inadequate
The gap between the opener and
hook is inadequate
Needle is inserted into wrong position
Needle is bent
Wrong direction
Bad timing of needle and hook
The length of the remaining upper
thread is too short
After trimming, lower thread holder
does not hold the lower thread
Due to problems in the up-stop
position of the needle, the thread take
up lever pulls the upper thread out of
the needle when the sewing starts
The height and distance between the
movable knife and the hook do not
match
Tension and contact of movable and
fixed knives are bad
Direction and height of
needle
Needle
Timing of feed dog
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
Thread tension
Thread take up spring
tension
Gap between opener
and hook
Direction and height of
needle
Needle
Threading
Gap between the
needle and the hook
Remaining upper
thread length after
trimming
Lower thread holder
Check the up-stop
position of the needle
The gap between the
movable knife and the
hook
Check the tension of
fixed knife