JUKI DNU-1541 Quick start guide

R
ENGINEER’S MANUAL
29353505
No.E349-01
1-Needle, Unison Feed, Lockstitch Machine
DNU-1541
1-Needle, Unison Feed, Lockstitch Machine
(with Safety Mechanism)
DNU-1541S
1-Needle, Unison Feed, Lockstitch Machine
(with Automatic Thread Trimmer)
DNU-1541-7

PREFACE
This Engineer’s Manual is written for the technical personnel who are responsible for the service and maintenance
of the machine.
The Instruction Manual for this machine intended for the maintenance personnel and operators at an apparel
factory contains operating instructions in detail. And this manual describes “Standard Adjustment”, Adjustment
Procedures”, “Results of Improper Adjustment”, and other important information which are not covered in the
Instruction Manual.
It is advisable to use the relevant Instruction Manual and Parts List together with this Engineer’s Manual when
carrying out the maintenance service of this machine.
Regarding the motor for the sewing machine with automatic thread trimmer, separately refer to the Instruction
Manual for the motor and Engineer’s Manual. In addition, for the control panel, refer to the Instruction Manual
for the control panel.
This manual gives the “Standard Adjustment” on the former page under which the most basic adjustment value
is described and on the latter page the “Adjustment Procedures” and “Results of Improper Adjustment” under
which the steps of adjusting procedure, and stitching errors and troubles arising from mechanical failures are
described.

CONTENTS
1. SPECIFICATIONS ...................................................................................1
2. STANDARD ADJUSTMENT....................................................................2
(1) Needle entry position .............................................................................................. 2
(2) Longitudinal position of the feed dog ...................................................................... 2
(3) Lateral position of the feed dog .............................................................................. 4
(4) Height of the feed dog ............................................................................................ 4
(5) Adjusting the opener (DNU-1541S) ........................................................................ 6
(6) Needle-to-hook timing............................................................................................. 6
(7) Lift of the presser foot ............................................................................................. 8
1) Hand lifter...................................................................................................................................... 8
2) Knee lifter ...................................................................................................................................... 8
(8) Feed motion.......................................................................................................... 10
1) Amount of alternate vertical movement....................................................................................... 10
2) Alternate momentum................................................................................................................... 12
(9) Feed cam timing ................................................................................................... 12
1) Horizontal feed cam timing.......................................................................................................... 12
2) Top feed cam timing.................................................................................................................... 14
(10) Needle sway (Optional selection only of DNU-1541-7) ........................................ 16
(11) Stitch length of normal/reverse feed ..................................................................... 16
(12) Balancer (DNU-1541, DNU-1541S)...................................................................... 18
(13) Position of the reverse feed control lever ............................................................. 20
(14) Safety clutch (DNU-1541S) .................................................................................. 22
(15) Lubrication ............................................................................................................ 22
3. STANDARD ADJUSTMENT OF THREAD TRIMMER COMPONENTS
(DNU-1541-7) .........................................................................................24
(1) Thread trimmer device.......................................................................................... 24
1) Cam follower ............................................................................................................................... 24
2) Solenoid arm ............................................................................................................................... 24
3) Thread trimmer cam timing ......................................................................................................... 26
4) Rotary knife and fixed knife......................................................................................................... 26
(2) Alternate vertical dial ............................................................................................ 28
(3) Adapting SC-380 to DNU-1541-7 ......................................................................... 30
4. INSTALLATION OF THE OPTIONAL PARTS ......................................32
(1) Automatic reverse feed device ............................................................................. 32
1) Removing the window plate (List of the parts to be removed) .................................................... 32
2) Removing the reverse feed control lever (List of the parts to be removed) ................................ 32
3) Installing the reverse feed link hinge screw (List A) .................................................................... 32
4) Installing the reverse feed control lever1. Reverse feed control lever (List B) ............................ 33
5) Installing the automatic reverse feed device (List C) .................................................................. 33
6) Installing the touch-back switch (List D)...................................................................................... 34
7) Installing the pneumatic components (List E) ............................................................................. 34
8) Parts list ...................................................................................................................................... 34
(2) Automatic presser foot lifter .................................................................................. 36
1) Installing the automatic presser foot lifter (List A) ....................................................................... 36
2) Installing the pneumatic device components .............................................................................. 37
3) Parts list ...................................................................................................................................... 38
(3) Installing the DL device......................................................................................... 40
1) When installing the DL device to DNU-1541-7 after set-up of the machine (List A) ................... 40
2) Installing the pneumatic device components (List B) .................................................................. 40
3) Installing the 5-step switch (List C) ............................................................................................. 40
4) Parts list ...................................................................................................................................... 41

5. PORTION TO WHICH LOCKTITE IS APPLIED ....................................42
6. SELECTIVE PARTS AND CONSUMABLE PARTS..............................43
7. ENGRAVED MARKER DOTS ON THE HANDWHEEL.........................44
8. LUBRICATION ROUTE DIAGRAM .......................................................44
9. PNEUMATIC PIPING .............................................................................45
10. MACHINE HEAD WIRING (WITH THREAD TRIMMER ONLY) ............46
(1) Connector coming from the machine head ........................................................... 46
(2) Connector coming from the pneumatic device ..................................................... 47
(3) Connector coming from the relay cable (Inserting side to the control box)........... 48
11. TABLE OFTROUBLES AND CORRECTIVE MEASURES................... 49
(1) With reagard to sewing ......................................................................................... 49
(2) With regard to lubrication...................................................................................... 50
(3) With regard to thread trimming ............................................................................. 51
(4) Others ................................................................................................................... 52
12. DRAWING OFTHETABLE .................................................................... 53

−1−
1. SPECIFICATIONS
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Item
Model
Model name
Application
Sewing speed
Needle
Thread possible to be
sewn
Thread possible to be
trimmed
Stitch length
Presser foot lift
Stitch length adjusting
mechanism
Reverse stitch selection
method
Thread take-up
Needle bar stroke
Alternate foot stroke
Hook
Feed mechanism
Top and bottom feed
actuation mechanism
Thread trimming
mechanism
Lubrication
Lubricating oil
Bed size
Free space for sewing
Size of handwheel
Motor
Specifications
DNU-1541
1-needle, unison-feed,
lockstitch machine
DNU-1541S
1-needle, unison-
feed,lockstitch machine
(with safety mechanism)
For heavy-weight materials
Max. 2,500 rpm
SCHMETZ 135 X 17 Nm 125 to 180 Standard : Nm 160
#30 to #5
Max. 9 mm (normal/reverse feed)
Hand lifter : 9 mm Knee lifter : 16 mm
By dial
Lever type
Slide thread take-up
36 mm
2.5 mm to 6.5 mm
Slot adjusting type
Horizontal-axis, 2-fold hook
Ellipse feed
By timing belt
Hook : automatic lubrication
Others : Concentration tank type oil wick lubrication (excluding some parts)
JUKI New Defrix Oil No. 2 (equivalent to ISO VG32)
476.6 mm x 178 mm
255 mm x 99 mm
V belt effective diameter : ø93.3 mm
Outer diameter : ø160 mm
2P, 400W
DNU-1541-7
1-needle, unison-feed
lockstitch machine (with
automaticthreadtrimmer)
Max. 3,000 rpm
#30 to #5
Air cylinder type (with
touch-back switch)
1 mm to 6.5 mm
Alternate foot stroke
adjusted by dial
Cam-driven scissors
type
SC-380

−2−
Standard Adjustment
Standard Adjustment
(2) Longitudinal position of the feed dog
2. STANDARD ADJUSTMENT
(1) Needle entry position
1
2
3
1
2
3
8±0.2 mm
60 mm
a’
a
A
Top surface of
throat plate
Conditions
• Needle bar at lowest
dead point
• Feed amount : 0 mm
Conditions
• Needle bar at lowest dead point
• Feed amount : 0 mm
A = Clearance between the feed dog and the throat plate
when the feed dog travels fully to the front.

−3−
Adjustment Procedures Results of Improper Adjustment
Adjustment Procedures Results of Improper Adjustment
1. Set the stitch dial to “0”.
2. Turn the handwheel to bring the needle bar to the lowest dead
point of its stroke.
3. Loosen clamping screw 1in the needle bar rocking rear arm.
4. Provide a clearance of 8 ±0.2 mm between presser bar 2and
walking bar 3and securely tighten the clamping screw.
(In the state that the presser foot is raised, adjust the clearance
to 8 ±0.2 mm at the position where the distance from the top
surface of the throat plate to the presser foot is 60 mm.)
(Caution) Tighten the screw so that the needle bar rocking
shaft has no thrust play.
™The throat plate comes in
contact with the feed dog and
contacting noise occurs and the
throat plate or the feed dog may
be damaged.
™Irregular stitches may result.
™Stitch skipping or needle
breakage will result.
™Poorly tensed stitches will result.
1. Set the stitch dial to “0”.
2. Turn the handwheel to bring the needle bar to the lowest dead
point of its stroke.
3. Loosen clamping screw 3in the feed rocker.
4. Move the feed base and adjust so that needle 1enters in the
center of the needle hole in feed dog 2. Then securely tighten
the clamping screw in the feed rocker.
(a = a’)
(Standard)
When the feed amount is maximum, A = approximately 1.5
mm.

−4−
Standard Adjustment
Standard Adjustment
(4) Height of the feed dog
(3) Lateral position of the feed dog
1
2
1
2
3
4
aa’ AB
A
Conditions
• Needle bar at lowest dead point
• Feed amount : 0 mm
Adjust the position to almost A = B.
Conditions
• Feed amount : 0 mm
• Height of feed dog is maximum.
Model Dimension A
DNU-1541 0.8 to 0.9 mm
DNU-1541S
DNU-1541-7 0.4 to 0.5 mm

−5−
Adjustment Procedures Results of Improper Adjustment
Adjustment Procedures Results of Improper Adjustment
1. Set the stitch dial to “0”.
2. Turn the handwheel to bring the needle bar to the lowest dead
point of its stroke.
3. Loosen the clamping screw in the feed rocker described in the
previous item (2).
4. Move the feed base and adjust so that needle 1enters in the
centerof feed dog2.Thensecurely tighten the clamping screw.
(a = a’)
In addition, adjust the lateral clearances (A, B) of the feed dog
in terms of the window of throat plate to almost equal values.
When the height of the feed dog is
higher than the specified value :
™Stitch pitch becomes larger than
the scale of the feed dial.
™Balloon stitches will result.
™Return of sewing product will
occur.
When the height of the feed dog is
lower than the specified value :
™Stitch pitch becomes smaller
than the scale of the feed dial.
™Feed force will be deteriorated.
™Stitch skipping or thread
breakage will result.
™Poorlytensed stitches will result.
™Needle breakage will result.
1. Set the stitch dial to “0”.
2. Turn the handwheel to bring the height of the feed dog to the
maximum.
(Bring the needle bar to the lowest dead point of its stroke.)
3. Loosen setscrew 1in the vertical feed bar shaft, turn vertical
feed bar shaft 2and adjust feed dog 3from top surface 4of
the throat plate (center section) to the dimension A. Then
securely tighten the setscrew.

−6−
Standard Adjustment
Standard Adjustment
(6) Needle-to-hook timing
(5) Adjusting the opener (DNU-1541S)
1
2
3
4
5
6
7
8
1
2
34
5
A
C
3
4
6
C
B
0.02 to 0.05 mm
A
Condition
• Swing angle of opener is maximum.
A = Clearance betwen top end of
opener 1and inner hook 7(Axial
direction)
B = Clearance between inner hook 7
and nail 8of inner hoop presser
when opener 1moves to front
end (Diameter direction)
C = Clearance between opener and
nail 2of inner hook 2when
opener 1moves to front end
(Diameter direction)
Conditions
• Feed amount : 0 mm
• Needle bar goes up from the lowest dead point.
Model Dimension A
DNU-1541 56.55 mm
DNU-1541S
DNU-1541-7 58.55 mm
8B