JUKI MF-7524 User manual

1
INSTRUCTION MANUAL
MF-7524

i
CONTENTS
Ⅰ. SPECIFICATIONS ..........................................................................................................1
Ⅱ. CONFIGURATION OF THE MACHINE COMPONENTS ...............................................2
Ⅲ.
INSTALLATION....................................................................................................................... 3
1. Installing the machine head onto the table........................................................................................ 3
2. Selecting the motor pulley and the belt ............................................................................................. 5
3. Installing the motor .............................................................................................................................. 5
4. Setting the belt .....................................................................................................................................6
5. Installing the belt cover .......................................................................................................................6
6. Installing the chain...............................................................................................................................6
7. Installing the thread guide................................................................................................................... 7
8. Installing the needle bar thread take-up cover.................................................................................. 7
Ⅳ. LUBRICATION AND OILING .........................................................................................8
1. Lubricating oil....................................................................................................................................... 8
2. Oiling .....................................................................................................................................................8
3. Silicon oil lubricating unit ...................................................................................................................9
Ⅴ. OPERATION.................................................................................................................10
1. Needle.................................................................................................................................................. 10
2. Attaching the needle ..........................................................................................................................10
3. Threading the machine head............................................................................................................. 11
4. Adjusting the stitch length ................................................................................................................12
5. Adjusting the differential feed ratio..................................................................................................13
6.
Adjusting the presser foot pressure......................................................................................................... 13
7. Adjusting the thread tension.............................................................................................................14
Ⅵ. ADJUSTING THE SEWING MACHINE .......................................................................15
1. Adjusting the silicon container thread guide .................................................................................. 15
2. Adjusting the rocking thread take-up............................................................................................... 16
3. Adjusting the rocking thread take-up thread receiver.................................................................... 17
4. Adjusting the rocking thread take-up thread receiver.................................................................... 18
5. Adjusting the looper thread cam ......................................................................................................18
6. Adjusting the looper thread cam eyelet ........................................................................................... 19
7. Adjusting the looper...........................................................................................................................20
8. Adjusting the height of the needle....................................................................................................21
9. Adjusting the rear needle guard .......................................................................................................22
10. Relation between the rocking thread take-up timing and the needle thread loop ....................... 23
11. Adjusting the height of the feed dog ................................................................................................24
12. Installing position of the spreader.................................................................................................... 25
13. Adjusting the spreader thread guide and the needle clamp thread guide.................................... 26
14. Adjusting the front needle guard......................................................................................................26
15.
Adjusting the presser foot lift .............................................................................................................27
16. Adjusting the micro-lifter...................................................................................................................27
17. Adjusting the feed locus....................................................................................................................28
18. Adjustment of the feed dog in longitudinal direction ..................................................................... 30
Ⅶ.
MAINTENANCE ....................................................................................................................31
1. Cleaning the sewing machine ........................................................................................................... 31
2. Replacing the lubricating oil ............................................................................................................. 31
3. Inspecing and replacing the oil lter................................................................................................ 32

– 1 –
Model name High-speed, at-bed coverstitch machine
Model MF-7524
Stitch typeI ISO standard 607
Example of application Lap seam to knits and jersey products
Sewing speed Max. 4200 sti/min (at the time of intermittent operation)
Speed of stitch at the delivery. 3500 sti/min (at the time of intermittent operation)
Needle gauge 4-needle ... 6.0 mm
Differential feed ratio 1 : 0.7 to 1 : 2 (stitch length : less than 2.5 mm)
Micro-differential feed adjustment mechanism is provided. (Micro-adjustment)
Stitch length 1.2 mm to delivery adjustment 3.6 mm (can be adjusted up to 4.4 mm)
Needle SMX1014B #9S to #12S (standard #10S)
Needle bar stroke 31 mm (33 mm: In the case the eccentric pin is changed over)
Dimensions (Height) 451 x (Width) 515 x (Length) 263
Weight 46kg
Lift of presser foot 4 mm (with top covering)
Micro-lifter mechanism is provided.
Feed adjustment
method
Main feed ... dial type stitch pitch adjustment method
Differential feed ... lever adjustment method (micro-adjustment mechanism is provided.)
Looper mechanism Spherical rod drive method
Lubricating system Forced lubrication method by gear pump
Lubricating oil JUKI GENUINE OIL 18
Oil reservoir capacity Oil gauge lower line : 600 cc to upper line : 900 cc
Installation Semi-submerged type
Noise
- Equivalent continuous emission sound pressure level (LpA) at the workstation :
A-weighted value of 75.5 dB; (Includes KpA = 2.5 dB);
according to ISO 10821- C.6.2 -ISO 11204 GR2 at 4,200 sti/min.
󰴸. SPECIFICATIONS

– 2 –
󰴹. CONFIGURATION OF THE MACHINE COMPONENTS
󰿿Presser spring regulator 󱢵Eye guard cover
󱀀Needle bar thread take-up cover 󱢶Throat plate
󱀁Oil circulation inspection windows 󱢷Needle tip silicon oil lubricating unit
󱀂Oil hole cap 󱢸Differential lock nut
󱀃Micro-lifter 󱢹Micro-adjustment knob
󱀄Needle thread silicon oil lubricating unit 󱢺Finger guard
󱀅Thread guide No. 1 󱢻Rocking thread take-up
󱀆Upper pulley 󱢼Front cover
󱀇Thread tension nut 󱢽Needle bar thread take-up thread receiver
󱢳Oil gauge 󱢾Silicon container thread guide
󱢴Feed regulating knob 󱢿Belt cover
󰿿
󱀀󱀁󱀂
󱀃
󱀄
󱀅
󱀆
󱀇
󱢳
󱢴
󱢶
󱢷
󱢺
󱢻
󱢿
󱢼
󱢾
󱢽
󱢹
󱢸
󱢵

– 3 –
[For the V-belt type]
Attach the supporting board and the rubber seats as shown
in the illustration and properly install the sewing machine.
󰿿 Bolt
󱀀 Spacer
󱀁 Washer
󱀂 Spring washer
󱀃 Nut
󱀄 Supporting board
󱀅 Spring pin
󱀆 Rubber cushion (Black) × 3
󱀇 Rubber cushion (Gray) × 1
1. Installing the machine head onto the table
Semi-submerged type
WARNING :
Do not insert the power plug of the motor into the receptacle until all works have been completed.
There is a danger of injury by being caught in the machine.
WARNING :
The weight of the sewing machine is more than 46 kg. Be sure to perform the work with two persons
or more in case of unpacking, transportation or installation.
󰴺.
INSTALLATION
󰿿
󱀀
󱀁
󱀂
󱀃
󱀄
󱀅
󱀆
󱀇
󰿿

󱀀
󱀀
■Installing the rubber cushion
Part No. Part name Q'ty
󰿿40072505 Dust-proof rubber
(Gray) 1
󱀀13155403 Dust-proof rubber
(Black) 3
Install the gray dust-proof rubber to section A only.
[For the V-belt type]

– 4 –
DRAWING OF TABLE (SEMI-SUBMERGED TYPE)
󱤨
4- ø 3.4 on the bottom surface, depth 20
(Drill a hole at the time of set-up.) 󱤩4-10.5 hole, depth 26, spot facing depth 3.5 󱤪2- ø 3.4 on the bottom surface, depth 10 (Drill a hole at the time of set-up.) 󱤫Drilled hole 17 󱤬
Installing position of drawer stopper
(on the reverse side)
Z-Z(4 locations)
Y-Y(3 locations)X-X
󱤨
󱤩
󱤪
󱤫
󱤬

– 5 –
Use a motor pulley which is adaptable to this sewing machine. The sewing speed exceeds the max. sewing
speed of this sewing machine and machine trouble will be caused unless a motor pulley which is adaptable
to this sewing machine is used.
When you use a new sewing machine, use the machine at a speed of 3,200 sti/min or less for the rst 200
hours (approximately one month). A good result can be obtained in terms of the durability.
Motor pulley and belt
Motor pulley
40˚
5.5 mm
10 mm
M type V belt
Use a clutch motor of 3-phase, 2-pole, 400 W (1/2HP).
Use the M type V belt.
1) The motor pulley shifts to the left-hand side when
depressing the pedal. At this time, install the motor so
that the centers of motor pulley and lower pulley align
with each other.
* For the installing procedure of the motor pulley, refer
to the Instruction Manual for motor.
Lower pulley
2) Install the motor so that the pulley rotates clockwise.
If the machine pulley rotates in the reverse
direction, nomal lubrication cannot be
performed. As a result, machine trouble
will be caused.
* The table shows the numbers
when a 3-phase 2-pole 400 W
clutch motor (1 / 2 HP) is used.
* The commercially-available motor
pulley near to the counted value
is designated since the outside
diameter of the commercially-
available motor pulley counts by
5 mm.
Sewing
speed
(sti/min)
50Hz 60Hz
Pulley size Belt size Pulley size Belt size
2,000 ø 45 M-32 ø 35 M-31
2,500 ø 55 M-32 ø 45 M-32
3,000 ø 65 M-33 ø 55 M-32
3,200 ø 70 M-34 ø 60 M-33
3,500 ø 75 M-34 ø 65 M-33
3,800 ø 80 M-34 ø 70 M-33
4,200 ø 90 M-35 ø 75 M-34
2. Selecting the motor pulley and the belt
3. Installing the motor

– 6 –
1) Fit belt 󰿿 to lower pulley 󱀀.
2) Turning upper pulley 󱀁, set the other side of the belt
to motor pulley 󱀂.
3) Adjust the belt tension so that the belt sags 15 to 20
mm when the center of the belt is pressed with an
approximate 10N (1.02 kgf) load.
4) Securely x the belt with lock nut 󱀃 when the belt has
been set.
If the deection of the belt is excessive
when the sewing machine is operated,
check again the belt tension.
󰿿
󱀁
󱀂
󱀃
󱀀
15 - 20mm
WARNING :
When replacing the belt, be sure to turn OFF the power to the motor and ascertain that the motor
has totally stopped rotating before starting the work. There is a danger of injury since hands or
clothes may be caught in the belt.
5. Installing the belt cover
WARNING :
Be sure to install the belt cover. If it is not installed, there is a danger of injury since hands or
clothes may be caught in the machine or a danger of damage of the machine since sewing products
may be caught in the machine.
4. Setting the belt
Install belt cover 󱀁 as shown in the illustration.
󰿿and 󱀀 are the xing screws for belt cover 󱀁.
1) Hang hook 󱀀 of chain 󰿿 to presser bar lifting lever
󱀁.
2) Hook the other side of the chain 󰿿 to the pedal.
󱀁
󱀀
󰿿
6. Installing the chain
󰿿
󱀀
󱀁

– 7 –
1) Install thread guide No. 1 󰿿 supplied as accessories
on the machine arm with screws (black, screw shank
length 6 mm) 󱀀.
2) Install thread guide 󱀁 on thread guide No. 1 󰿿 with
screw (black, screw shank length 6 mm) 󱀂.
7. Installing the thread guide
󰿿
󱀀
󱀂
󱀁
8. Installing the needle bar thread take-up cover
󰿿
󰿿
Install the needle bar thread take-up cover supplied with
the unit on the machine arm with two screws 󰿿.

– 8 –
<When using the sewing machine for the rst time>
Lubricating oil has been taken out at the time of delivery.
Be sure to supply lubricating oil before using the sewing
machine for the rst time.
• Oil used : JUKI GENUINE OIL 18
Do not use oil addition agent since deterio-
ration of lubricating oil or machine trouble
will be caused.
To add oil, remove rst the oil inlet cap 󱀀 indicated as
"OIL". Then, add oil from the oil inlet until the oil surface
reaches the middle of the upper and lower marker lines
on oil gauge 󰿿.
<Checking before using the sewing machine>
1) Check oil gauge 󰿿 and make sure that lubricating oil
level is between the upper and lower two lines. When
lubricating oil level lowers below the lower line, supply
lubricating oil.
2) Make sure that lubricating oil comes out from the
nozzle of oil circulation identication window 󱀁when
rotating the sewing machine. When lubricating oil
does not come out, perform “󰴾-3Inspecting and
replacing the oil lter”. (See page 32.)
1. Lubricating oil
Lubrication
󰴻. LUBRICATION AND OILING
When you operate the sewing machine for the rst time
or after an extended period of disuse, be sure to apply
2 to 3 drops of lubricating oil to needle bar 󱀂.
For the lubricating oil, use JUKI GENUINE OIL 18.
2. Oiling
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the follow-
ing work after turning the power off and ascertaining that the motor is at rest.
󱀂
󰿿
󱀀
󱀁

– 9 –
3. Silicon oil lubricating unit
This sewing machine is provided with the silicon oil
lubricating unit as standard.In case of sewing at a high
speed, or using chemical thread or chemical fabric, use
the silicon oil lubricating unit to prevent thread breakage or
stitch skipping.
Oil used is silicon oil (dimethyl silicon).
Open cover 󱀀 of silicon container 󰿿 and make sure that
silicon oil enters needle thread, needle tip and silicon oil
lubricating unit. If silicon oil is insufcient there, supply it
(dimethyl silicon).
When silicon oil adhered to the components
other than the silicon oil lubricating unit, be
sure to wipe it out. If the components to which
silicon oil adhered are kept without wiping out
the oil, sewing machine trouble will be caused.
󰿿
󰿿
󱀀
󱀀

– 10 –
The needle used for this sewing machine is
SM1014B.
For the needle No., select a proper needle in
accordance with the sewing conditions.
2. Attaching the needle
1) Loosen setscrew 󱀀of needle 󰿿 with a screwdriver.
2) Hold the new needle with indented part facing to the
rear and insert it into the hole in needle clamp 󱀁 until
the end of hole is reached.
3) Securely tighten setscrew 󱀀 of the needle󰿿.
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the
following work after turning the power off and ascertaining that the motor is at rest.
1. Needle
󰴼. OPERATION
󰿿
󱀀
󱀁
󰾰Scarf


Japan No. 9 10 11 12
German No. 65 70 75 80

– 11 –
󰿿
󱀁
󱤩
󱤪󱤫
󱤬
󱀀
3. Threading the machine head
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the follow-
ing work after turning the power off and ascertaining that the motor is at rest. If threading is wrong, stitch
skipping, thread breakage, needle breakage or irregular stitches will be caused. So, be careful.
When using more stretchable thread
When covering thread is excessively
loosened = 󱤩
When covering thread is excessively
loosened even after passing 󱤩= 󱤪
When covering thread is
excessively tense = 󱤫
Broken line 󱤬when using more
stretchable thread
Thread the machine head according to the following threading illustrations.
󱀀
󰿿
󱀁

– 12 –
4. Adjusting the stitch length
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the follow-
ing work after turning the power off and ascertaining that the motor is at rest.
The stitch length can be innitely adjusted from 1.2 mm
to 3.6 mm.
* The actually sewn stitch length varies in accordance
with kind and thickness of the materials.
[How to change the stitch length]
Turn clockwise feed regulating knob 󰿿 to increase the
stitch length.
Turn it counterclockwise to decrease the stitch length.
• When making the stitch length 3.6 mm or more
Loosen screw 󱀀 and turn clockwise feed regulating knob
󰿿 to regulate the stitch length.
Push pin 󱀁 until it goes to the end, and x it with screw 󱀀.
Use the machine within the range where feed dogs or
feed dog and throat plate do not come in contact with
each other.
󰿿
󱀀
󱀀
󱀁
󱀁
󰿿

– 13 –
Loosen differential lock nut 󰿿 and move lever 󱀀 up to
increase the differential feed ratio. Then the sewn material
is gathered.
Move lever 󱀀 down to decrease the differential feed ratio.
The differential feed ratio becomes 1 : 1 at the position
where the pointer of lever 󱀀 is on the long scale. Note
that two scales on the upper side show 1 : 1.4 and 1 : 2
respectively, and one on the lower side 1 : 0.7.
Fine adjustment of the differential feed ratio can be
performed with micro-adjustment knob 󱀁.
There is a case where feed dogs or feed dog
and throat plate come in contact with each
other by the aforementioned adjustment
according to the relation between the stitch
length and the differential feed ratio. So, be
very careful.
5. Adjusting the differential feed ratio
Gathering
Stretching
Decrease the presser foot pressure as low as possible
to such an extent that stitches are stabilized.
To adjust the pressure, loosen lock nut 󱀀 of presser
spring regulator 󰿿 and turn presser spring regulator 󰿿.
After the adjustment, tighten lock nut 󱀀.
Turning it clockwise to increase the pressure.
Turning it counterclockwise to decrease the pressure.
6. Adjusting the presser foot pressure
󰿿
󱀀
󱀁
󰿿
󱀀
󱀀

– 14 –
Decrease
7. Adjusting the thread tension
Adjust the thread tension with the following thread tension
nuts.
󰿿 Needle thread tension nut
󱀀 Top covering thread tension nut
󱀁 Looper thread tension nut
Turn clockwise to increase the thread tension.
Turn counterclockwise to decrease the thread tension.
Increase
󰿿
󱀀
󱀁

– 15 –
1) Loosen setscrews 󰿿, adjust so that 12 mm is given
from the center of the upper screw to the top surface
of thread guide, and tighten the thread guide with
setscrews 󰿿.
2) Loosen setscrew 󱀀 and adjust the position from the
center of screws 󰿿 to the center of needle thread
guide rod to the extreme right position (38 mm). Then
tighten screw 󱀀 to x the thread guide rod.
A B C D
17mm 22mm 28mm 31mm
(38 mm)
12 mm
󱀀󰿿
󰴽. ADJUSTING THE SEWING MACHINE
1. Adjusting the silicon container thread guide
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the
following work after turning the power off and ascertaining that the motor is at rest.
3) Loosen setscrews 󱀁 and adjust so that the heights
of the respective needle thread guide rods are the
dimensions as shown in the illustration. Then tighten
screws 󱀁 to x the thread guide rods.
A
B
C
󱀁
D

– 16 –
1) Loosen setscrews 󰿿, move rocking thread take-up 󱀀
to the right and left, adjust so that 90 mm is given from
the thread hole to the center of rocking thread take-up
shaft 󱀁, and x setscrews 󰿿 as shown in the gure.
2) Adjust rocking thread take-up base 󱀂 so that it is
positioned horizontally when the rocking thread take-
up is in its lowest point, and x it with screw 󱀃.
󰿿
󱀀
󱀁
󱀃
90mm
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the
following work after turning the power off and ascertaining that the motor is at rest.
2. Adjusting the rocking thread take-up

– 17 –
1) Loosen four setscrews 󰿿 in the needle thread
receiver plate, and adjust the height. Adjust the left
medium needle only to 5 mm and securely tighten the
setscrews.
Align the height of the other needle thread receiving
plates with the needle thread receiving base and x.
The size of needle thread loop can be changed by
adjusting the height according to the kinds of needle
thread.
5 mm
󰿿
2) Bring the needle bar to its lowest position, loosen
setscrew 󱀀 to adjust so that the needle thread comes
is contact with the thread receiver of the front needle
thread, and x the thread receiver with setscrew 󱀀.
Front needle thread
󱀀
3. Adjusting the rocking thread take-up thread receiver
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the
following work after turning the power off and ascertaining that the motor is at rest.

– 18 –
󰿿
󱀀
󱀁
󱀂
󰿿
󱀀
󱀁
󱀂
󱀂
󱀀
󰿿
4. Adjusting the spreader thread guide
Adjust so that the top end of thread guide thread path
(rear) 󱀁 of spreader thread guide 󱀀 aligns with the
bottom surface of slot of spreader thread take-up 󰿿when
spreader thread take-up 󰿿 is in its highest position. Then
tighten screw 󱀂 to x the spreader thread guide.
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the
following work after turning the power off and ascertaining that the motor is at rest.
5. Adjusting the looper thread cam
Adjust so that thread comes off from the highest place of
looper thread cam 󱀀 when needles come down and the
top end of left needle 󱀁 aligns with the bottom surface
of looper 󱀂. Then tighten screws 󰿿 to x the looper
thread cam.
Thread
WARNING :
To protect against possible personal injury due to abrupt start of the machine, be sure to start the
following work after turning the power off and ascertaining that the motor is at rest.