Juki LS-341N Instruction Manual

CYLINDER-BED, 1-NEEDLE, UNISON-FEED lOCKSTITCH

MACHINE (WITH

A VERTICAl-AXIS tiOOK)

1

®

I

I

----

NOTE : Read safety instructions carefully and understand them

before using your
Retain this Instruction Manual for future reference.

LS-341

N.

No.02

29176906

---------

IMPORTANT SAFETY INSTRUCTIONS

----

Congratulations on
To

get the most
correctly.
Please read
Please remember

this

1. Observe the basic safety measures, including, but

2.

Read all the instructions, including, but not limited
keep

this

3.

Use the machine after

4.

All safety devices must be in position when the machine is ready
specified

5.

This machine shall be operated

6.

For

your

7.

For the following, turn

7-1

For threading needle(s), looper, spreader etc. and replacing bobbin.

7-2 For replacing part(s)

guide etc.

7-3

For repair work.
When leaving the working place

7-4
7-5 When using

8.

If you should allow oil, grease, etc. used with the machine and devices
swallow any

9.

Tampering with the live parts and devices, regardless

10.

Repair, remodeling and adjustment
personnel. Only

11. General maintenance and inspection

12. Repair and maintenance

the audit and guidance

Whenever you

13. Before making repair and maintenance

the

air

compressor
residual air
are

only

personnel.

14. Periodically clean the machine

your

purchase

out

of

the many

Instruction Manual carefully before use.

to

keep

this

Instruction Manual so that

it

safety devices

personal protection, we recommend that you wear safety glasses.

off

clutch motors

of

such liquid by mistake, immediately wash the contacted areas and consult a medical doctor.

spare parts designated by JUKI can

of

find a failure

has

pressure after disconnecting the air comp1ressor from the machine has

adjustments

and

of

a JUKI machine.

functions

manual in a safe place.

has been ascertained that

is

not allowed.

by

the power switch

of

needle,

without

works

of electrical components shall be conducted by qualified electric technicians

specially skilled personnel.

of

any

to

be detached from the machine and the compressed air

performance

throughout

of

this

machine and operate it in safety, it

We

hope you will enjoy the use

not

limited

to

this

you

may read

appropriately-traine~d

presse1r

or

works

of

foot, throat plate, looper, spreader, feed dog,

when the
applying brake, it has

must

works

electrical components, immediately stop the machine.

works

checks

the period

it

at anytime when necessary.

it

conforms

or

disconnect the power plug

working

of

only

be done by appropriately trained technicians

be

have

to

be done

on the machine equipped with pneumatic parts such as an air cylinder,

done

of

to

Instruction Manual before you use the machine. In addition,

operators.

place

to

whether the machine is powered, is prohibited.

used

for

by

by

appropriately

use.

is

necessary

of

your

the following ones, whenever you use the machine.

with safety rules/standards valid in

for

work

or in operation. The operation without the

of

the machine from

is

unattended.

be

waited until the

to

come

repairs.

appropriately trained personnel.

iru

trained

motor

stopped totally.

contact with

supply

to

be expelled. Exceptions

technicians

machine

th1~

neeoHe

has

to

to

use

this

machine

for

a long time.

your

country.

receptacle.

guard, folder, cloth

~rour

eyes

or

skin

or

specially skilled

or

under

be

cult

off. Existing

to

<Or

specially

skilled

or

this

15. Grounding the machine

in an environment that is free from

16. An appropriate power plug has

to

a grounded receptacle.

17. The machine is

18. Remodel

measures. JUKI assumes

or

only

modify

is

always necessawy

to

allowed

the machine in accordance with the safety rules/standards while taking all the effective safety

to

be

n.o

responsibility

19. Warning hints are marked with the

Danger of injury to operator

A

Items requiring special attention

&

strong

be attached

u·sed

two

noise sources such as high-frequency welder.

for

the purpose intended. Other used are not allowed.

shown symbols.

for

the

no1rmal

to

the machine by electric technicians. Power plug has

for

damag1e

or

service staff

operation

caused by remodeling

of

the machine. The machine has

or

modification

to

to

be

of

the machine.

be operated

connected

-j-

-----FOR

1.

Keep

yourr

hands away from needle when you

machine is in operation.

2.

During operation, be careful
come close
do

not

3

..

Do

not

removed.

4.

Before tilting the mach
attached

5.

Before tilting the machine

confirm

and

6.

Tilt the machine head after removing the

7.

When having tilted the machine head, wipe

lbed

support

8.

"fo ensure safety, never operate the machine with the ground wire

removed.

9.

When inserting/removing the power plug,

advance.

10. In time
t:he

receptacle

·11.

If the machine is suddenly moved from a cold place
may be observed. In

(~onfirmed

12. lrurn OFF the power

13. Do

not

to

the thread take-up, handwheel, V-belt, bobbin winder and motor. Also,
place anything close
operate

of

allow the power cord

yom

to

your

machine head.

that the

and hinge area, and then raise up the machine head.

thunder and

so

as

that there is no danger

SAFE

machine with

nne

head, be sure

or

motor

to

to

of

~ightening,

ensure safety.

this

case,

the machine in

OPERATION---------

not

to

allow

to

them.

the~

removnng the V belt, be sure to

the sewing machine stops.

stop

turn

of

to

trail

tum

ON

your

or

any other person's head

finger guard, belt cover and any other protectors

to

confirm that the head support bar is

hook

for

the knee lifter.

out

oil on the bed underside, the

the

your

ON

water

the

on

the floor.

work

the

drops

event

power

power

switch

and disconnect the power plug from

to

a warm place, dew condensation

to

in the machine.

of

a power failure.

the power

tum

OFF the power switch

has

the

machine

switch

for

to

or

while

or

hands

pro_perly

top

the power
be turned OFF in

after

your

the

to

face

of

supply

have

-n-

[!. SETTING UP THE SEWING MACHINE

Mounting

(Caution)

j2.

LUBRICATION

the

WARNING:

Turn OFF

knee

The knee
is

installed.

the

power

lifter

lifter

should

before

be

mounted

starting

the

before

work

so

as

the

to

motor

prevent

accidents

When using the knee liifting pedal, attach knee
lifter bracket A

8 in place using screws as

illustrated in the figure.

(Caution)

caused

by

Knee
screws
machine

abrupt

start

iifler

~~

in

ol

the

bracket

are

supplied

the

accessory

sewing

8 and

with

machine.

the

box.

*

*

*

-2-

Before

Prior
points marked with the arrows.

Lubricating

Shift the slide plate, and apply two or three drops
every day to the hole shown with the arrow And
four or five drops
with the arrow

Lubricating

Prior
holes shown with the arrows

starting the sewing

to

operation, apply adequate amount

the

hook

of

oil every day to the felt shown

and

machine

hook

4D.

the

feed

bar

to

operation, apply two or three drops

(i,

(g

and@

of

shaft

without fail.

oil

saddle

of

oil to the

to

of

the

oil

j3,

INSTALLING

THE

THREAD

STAND

!4.

~NSTALUNG

THE BELT COVER AND THE BOBBIN WINDER

Assembk
side edge

the thread stand, and install it on the far right-hand

of

the table using three screws

WARNING:

Turn

OFF

accidents caused by abrupt start

1)

Drill guide
in the table.

2) Insert belt cover support
machine arm.

3) Install belt cover support plate

4) Attach belt

5) Fit bobbin winder 8 in belt cover
position

6) Fix bobbin

7) Put the V belt
cover and top

the power before starting the work so as

holeseand@for

of

wooden screws

0 into the tapped hole in the

f)

on the machine head.

cover@! to support

of

the bobbin winder properly.
winder@ on the table.

on

the hand wheel. Attach rid

cover8

in place.

Oand

Q.

to

the sewing machine.

support plate

@!,

prevent

to

be used

f).

and adjust the

Gof

the belt

ATTACHING THE NEEDLE

~

5.

-

__Q_]B;/-8

'-tlr

:....--~

~~·

[s.

ATTACHING/REMOVING THE BOBBIN CASE

.A

• Turn OFF the

1)

2) Loosen needle clamp screw

3)

4) Securely tighten the needle clamp screw

~----------------------------------,

WARNING:

Turn

OFF

accidents caused by abrupt start

Turn the handwheel

highest position.

indented
Insert the needle into the needle bar until it will go no
further.

the power before starting the work so as to prevent

power

part(i.) faces exactly to the right.

to

the motor.

to

move the needle bar up to its

of

the sewing machine.

f).

Hold needle 0 so that its

@.

WARNING:

Turn

OFF

the power before starting the work so as

of

accidents caused by abrupt start

1)

Raise lever 0

together with the bobbin in it.

2) Fit the bobbin case into the hook driving shaft, and tilt the
lever.

of

the hook, and remove the bobbin case

the sewing machine.

to

prevent

-3-

11.

WINDING A BOBBIN

Is.

PLACING A BOBBIN IN

TH~

BOBBIN CASE

1)

Route the thread in the order
winding it round the bobbin several times.

bobbin

2) Set
with the belt.

3) Adjust
round the bobbin so that the bobbin is wound with thread
about 80%
incn·--ase
counterclockwise to decrease it.

4)

If

thread is wound unevenly round the bobbin, move

winder tension adjuster base

thread is evenly wound round the bobbin.

5) The moment the bobbin has been wound up, the bobbin

presser is released, and the bobbin winder

automatically.

presserOdown

screw8to

of

its capacity.

the amount

adjust the amount

of

thread wound round the bobbin, or

of~,@

to

bring the winder in contact

Tum

the screw clockwise

0

to

the right or left so that

of

thread to

and

@before

be

wound

will stop

to

WARNING:

Turn

OFF

the

power

before

starting

the

work

so

as

to

prevent

accidents

1)

Hold a bobbin so that the end
the bobbin is directed
case.

2) Pass the thread in threading slit
it under the tension spring and draw

(Caution)

caused

by

to

As

long

as

the

the

bobbin

tion ~ makes

case,

@.

abrupt start

the right and put it into the bobbin

bobbin

the

of

the

sewing

machine.

of

the thread wound round

4itin the bobbin case, route

it out from notch

is

pulling

b<>bbin

correctly

the

rotate

thread

in

placed in

in direc-

direction

8.

19.

THREADING THE MACHINE HEAD

WARNING:

Turn

OFF

the power before starting the

Thread the
in

the

machine

order

as

illustrated

of 0 through

~.

in

the

work

figure

so

as

to

prevent accidents caused

by

abrupt start

of

the sewing machine.

-4-

!10. ADJUSTING

THE

STITCH LENGTH

!11. THREAD TENSION

Tum stitch length dial 8 counterclockwise or clockwise

bring the desired value
is aligned with

the pin.

to

the top

of

the dial so that the value

* Reverse feed stitching

1)

Push down feed

2) The machine performs reverse feed stitching as long
the lever is held depressed.

3) The moment you release
the normal stitching mode.

leverfj.

the lever, the machine resumed

* Adjusting the needle thread tension

Tum tension nut No. 2 8 clockwise

crease
(toward@) to decrease it.

the needle thread tension, or counterclockwise

(toward~)

to in-

* Adjusting the bobbin thread tension

Tum tension
the bobbin thread tension,

@)

to decrease it.

screw@

clockwise (toward@) to increase

or

counterclockwise (toward

to

as

@.

THREAD TAKE-UP SPRING

* To change the stroke

1)

Loosen screw@ in the stopper, and move stopper8lto
right

or

left.

2) Move the stopper
thread take-up spring, or to the left to decrease it.

* To change the

spring

Loosen
increase the tension
it. Fit a screwdriver in

tum it until the desired tension is provided.

nutO.

~ension

Tum spring shaft 0 counterclockwise to

of

thread take-up spring 8

to

the right to increase the stroke

of

the thread take-up

of

the spring,

the groove in the spring shaft and

or

clockwise to decrease

of

the

the

--5-

113. ADJUSTING THE PRESSURE OF THE PRESSER FOOT

@.

ADJUSTING THE PRESSER FOOT

r----

J!\ND

,

Adjust the pressure
type

of

material to

spring regulator: 25 mm)

1) Turn pressure spring regulator

increase the pressure

wise (toward@) to decrease

2) After lhe adjustment, securely tighten

lator

..

of

the presser foot in accordance wilh the

be

used. (Standard height

Oclockwise

of

the presser foot,

it.

THE WALKING FOOT :

* Operating height

presser

The operating height
foot has been adjusted to the marker
the top feed crank. A better
adjusting
presser foot.

""

o Highest position
o Lowest position

foot

the operating height

Loosen nut
boss accordingly.

of

the walking

of

the walking foot and the presser

result may be obtained by

of

G.

and change the position

-> The stroke is

---J>

The stroke is minimized.@

of

the pressure

(toward~)

or

counterclock-

nut@

of

ffoot

and the

of"

1/8" engraved on

the walking foot and the

of

the cam rod

maximized.~

to

the regu-

l

* Alternate vertical

and presser foot

The alternate vertical strokes
presser foot are normally equaL

1)

Loosen screw 8

2) Bring

~

the thread take-up lever to its highest position,
and lower the presser bar lifting lever.
Move

top feed crank
of

the presser foot,

motions

of

the top feed crank.

@to

or

to the

of

the walking foot

of

the walking foot and

left~

to increase the stroke

right@

to increase it.

-6-

[

15.

HEIGHT OF THE FEED

DOG

j16.

NEEDLE-TO-HOOK RELATIONSHIP

WARNING:

Turn

OFf

the power before starting the

work

0

so

as

-0.05mm

to

Feed dog
the surface
to be adjusted according the sewing conditions or after the
feed dog is replaced, follow the procedure described below.

1) Maximize the feed dog height.

2)

3)

4)

prevent accidents caused by abrupt start

Adjust lhe timing between the needle and the hook following
the procedure described below.

I) Set

2) Turn the hand wheel to bring the neeqle bar to the lowest

* Det,ermine the height

3) The standard height

Ohas

been factory-adjusted

of

throat plate@. When the feed dog height needs

Loosen screw 8

Adjust the feed dog height comparatively higher than the

standard height, and temporarily

Now, adjust the height
securely tighten the screw 0

1tbe

feed regulating dial to "3".

position
screwO.

of

in

the feed dog.

of

the feed dog appropriately, and

its stroke, and loosen needle bar connection

of

of

the needle bar is obtained when a

distance

needle eyelet and blade point 0

needle ascends 2.4 mm from the lowest position
stroke.

(The lowest position

of

1.

7 mm is provided between the

of

the needle bar

reference)

Distance from the bottom face

the bottom end

*

Det1ermine

4) Loosen
@and

5)

In the state described in 3), loosen screw 8

driving shaft saddle and move the hook driving shaft

saddle to the right or left until a clearance
is provided between the blade point

screw@

loosen screws

of

the needle bar: 55.2 mm

the

position

in the gear cover@, remove gear cover

of

Oand

fi. After the adjustment, securely tighten the screw.

6) Then, align the blade point

the needle, and tighten screw e

7) Tum the handwheel clockwise and alternately tighten
screws(!) little by little.
(Never tighten either screw only.)

of

to

jut

outl

mm from

fix

it

at that position.

in

the feed dog.

of

the sewing machine.

the needle bar.

LOp

end

of

of

the hook when the

of

for

of

the needle bar frame to

the

hook

(i)in the large bevel gear.

in

the hook

of 0 to

0.05

of

the hook and needle

the hook with the center

in

the gear.

the

its

mm

of

-7-·

117.

ADJUSTING THE NEEDLE GUARD OF THE HOOK

the

-

work

so

as

to

_

prevent

I

accidents

After replacing the hook, be sure to confirm the position
needle guard. The standard position
obtained when needle

the side face
adjust
ingly.

1) To bend the needle guard inward, apply a screwdriver

2) To bed the needle guard outward, apply a screwdriver

caused

the position

the outside

the inside

WARNING:

Turn

OFF the

power

before

starting

j_

[

__________

USTING THE BOBBIN CASE OPENING

WARNING:

Tt~m_Off

the

power

before

starting

the

work

so

as

to

prevent

accidents

1)

2)

caused

Tum

the handwheel in its normal rotational direction to
bring bobbin case opening lever
tion.
Tum

bobbin case @ in the direction

stopper8comes

0.

3) Loosen
ment plate and move bobbin case opening lever adjust­ment plate
clearance

bobbin case opening lever

the bobbin case.

screw8in

--

by

abmpt

start

of

the

sewing

of

guard@lightly

of

needle as illustrated in the figure.

of

the needle guard

of

the needle guard.

of

the needle guard.

by

abmpt

start

in contact with the groove in throat plate

the bobbin case opening lever adjust-

8 in the direction

of

0.1 to 0.15 mm is provided between the

comes in contact with

by

.

of

the

sewing

4~to

of

the arrow so that a

and protruding section

machine.

the needle guard is

bending it accord-

-·--

machine.

its back end posi-

of

arrow @ until

J

of

the

If

not,

to

to

J

:

of

OJ.

ADJUSTING THE

LONGITUDINAl

POSITION OF THE NEEDLE BAR FRAME ]

* Adjusting the relationship between the top

feed rod and presser bar

1) Set the feed regulating dial to its minimum value.

2) Loosen clamping screw in
arm, and adjust the clearance between the top feed rod and
the presser bar to 7.5 mm.

(Caution) Take care

frame@.

not

* Adjusting the relationship between the feed

and the needle bar

dog

1)

Set

the feed regulating dial to its minimum value.

2) Loosen clamping screw in the feed rock

3) Adjust
comes
(slightly closer

the position

to the center

of

of

to the operator).

the needle bar frame rear

to

allow

any

play in needle bar

shaft crank.

the feed dog so that the needle

the

needle hole in the feed dog

-8-

!20. SAFETY MECHANISM

WARNING:

Turn

OFF

accidents caused by abrupt start

If

the thread is

operation, the safety

is in
lower sprocket only.

* How

1)

Remove

2) Pressing
direction opposite to its normal rotational direction.

the power before starting the work so as

caught

in the hook while the sewing machine

mechanism

to

reset

the

thread

caught

in the hook.

push

button

8,

strongly

of

the sewing machine.

actuates to idle the

tum

the pulley in the

* Safety load

Tum

adjustment
incre-ase the safety load,
wise) to decrease it.

screw@

in

direction~

or

in direction

@(counterclock-

(clockwise) to

to

prevent

!21.

REPLACING THE TIMING BELT

.

-""-

I~

v

(D

\l

1\

,--

~

""'

~I

G)

-

-

G)

~

WARNING:

Turn

OFF

the power before starting the work so as to prevent

accidents caused by abrupt start

* How

1) Loosen

2)

3)

4)

* How

1) Installation is carried

2)

to

remove

screwOin
rear bushing (2), screw
clamping screws

0in

the

feed lever

Remove

bushingO.
Draw
timing
Remove
from the side
main shaft rear bushing.

To
driving shaft,

up

engraved on the hook driving shaft thrust

marker

ing

sproclk:ete.

handwheel

feed lever

belt

the timing belt from the

to

install

adjust the timing between the main shaft

to its

highest

line~)

(D.

In this state, insert the timing belt into lower

the

timing

the

hand

Oin

0 in the feed

shaft

8,

shaft

fi)until a clearance

8 to

come

off

window

tum

engraved

and pull

the

timing

out

the hand wheel to bring the thread take-

dead

belt

wheel,

the main shaft rear bushing,

lever

in the written order.

a11d

pull

is provided.

out

belt

analogously in reverse order.

point

and

on

hook

of

the sewing machine.

screws@in

shaft arm and screw

out

lower

it from the hole in the

the

driving

main shaft

main shaft rear

enough

sprocket, draw it

screw

to allow

and

the hook

No. 1

collar®

shaft rear bush-

G)

with

-9-

@_i

1.

MOTOR PULLEY AND V

Use an M type V belt.

B!LT

2. The following table show the relationship between the motor pulley,

belt length and the rotational speed

of

the sewing machine.

_]

Rotational speed

of

sewing machine

Frequency

50Hz

2000 s.p.m

60Hz

The

effective
When
above.

your

diameter

machine

cr!

the

motor

pulley

uses a single-phase

is 5 mm

motor,

smail0r

apply the

IN SEWING AND CORRECTIVE

F--·

Trouble

-----~---

l.

Thread breakage

I

.

CD

The

thread path, needle point, blade point

I (Thread frays or hook or the stopper groove in the throat plate has

wears out.)

(Needle thread remains

to

3 em on the wrong ®

2

of

the cloth.) tension while it has an <:xcessively small stroke.

side

2. Stitch skipping

3. Loose stitches
(isolated idling
loop)

scratches.
The

1<2)

Q)

®

@

(J)

(j)

<2)

Q)

®

@

®

(J)

@

needle thread tension

The

clearance in the bobbin case opening lever is 0

too large.

The

needle comes in contact with the blade point
the hook.
The

needle thread tension is too low. 0
The

thread take-up spring has an excessively high 0

The

timing between the needle and hook too early 0

or too late.

The

clearance between the needle and the blade 0
point
The

timing between the needle and hook

or too late.

The

presser foot pressure is too low. 0
The

height

The

needle guard

The

size
Defective needle thread path.
The

hook has scratches.

(j)

The

<2)

Q)

®

@

®

thread path is

The

bobbin fails
The

clearance in the bobbin case opening lever is

too large.

The

bobbin thtead tension
The

bobbin thtead

the bobbin.

The

forked part

case is

Cause j

is

too high.

of

the hook

of

not

is

too large.

of

the needle bar is inadequate.

of

the hook does not function.

the needle is wrong.

poody

to

of

threaded.

finished.

rotate smoothly.

is

too low.

has

been

wound too tight round

the

t<ension

spring

of

of

the

is

too early 0

the bobbin

Outside diameter

of

motor

I

I

0115 mm

095mm

~-

than

'lhe

out,ide

belt

which

is i inch

-,.---···-------------·

Remove the scratches

I o 1

using a fine emery paper.

in the throat plate.
Adjust the needle thread tension properly.

0

Decrease the clearance in the bobbin case opening
lever. Refer

opening lever".

I o

of

Refer

Adjust the needle thread tension properly.
Decrease the tension
increase the stroke
Refer

Refer

Refer

Tighten the pressure spring regulator.

Refer

0

Refer to "17. Adjusting the needle guard

0

hook".
Replace the needle by one which

0

See "9. Threading the machine head".

0

Remove the scratches

0

using a fine emery paper.
Grind it using a fine emery paper, or

0
0 Replace the bobbin, or replace the hook.

See "18. Adjusting the bobbin case opening lever".

0

0 Properly adjust the bobbin thread tension.

Decrease the bobbin thread winding tension.

0

Correctly thread the bobbin case.

0

diameter.

than

Corrective

on

the blade point

Buff

to

"18. Adjusting the bobbin case

to

"16. Needl<Ho-hook relationship".

of

the thread take-up spring, and

of

the spring.

to

"16. Needle-to-hook relationship".

-

to

"16. Needle-to-hook relationship".

to

"16. Needle-to-hook relationship".

to

"16. Needle-to-hook relationship".

on

the blade point

Size

of

V belt

M57

lVI56

those

meas~nas

up the stopper groove

is

in the table

of

the hook

of

one count thicker.

of

the hook

buff

it up.

l

--~---

the

-10-

MEMO

-------

-----------------

·-----------------------------·-----··-------

·--

·-------

--·---

To order

or

for further information, please

contact:

JUKI

INTERNATIONAL SALES DIVISION

8-2-1, KOKURYO-CHO,
CHOFU-SHI, TOKYO
PHONE: 03 (3430)
FAX.
TElEX

CORPORATION

182, JAPAN

4001-5

03(3430) 4909·4914·4984

: J22967

L.

___

Please do not hesitate to contact our distributors or agents

*The

description covered in this instruction manual is subject

commodity without notice.

_

in

your area for further information when necessary.

to

change for improvement

96 • 04 Printed

in

Japan

of

the

(F)