Juki DDL-8700-7 Engineer's Manual

®
1-Needle, Lockstitch Machine
with Automatic Thread Trimmer
DDL-8700-7
ENGINEER’S MANUAL
40094273
No.E395-00
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 these machines intended for the maintenance personnel and operators at an
apparel factory contains operating instructions in detail.
It is advisable to use the Instruction Manual and Parts List for SC-920 together with this Engineer's Manual
when carrying out the maintenance of these machines.
This manual gives the "Standard Adjustment" on the former section under which the most basic adjustment
value is described and on the latter section the "Results of Improper Adjustment" under which stitching errors
and troubles arising from mechanical failures and "How To Adjust" are described.
CONTENTS
1. GENERAL ......................................................................................................1
(1) Features .................................................................................................................................. 1
(2) Applications ............................................................................................................................ 1
2. SPECIFICATIONS ........................................................................................ 2
3. NAME OF EACH COMPONENT .................................................................. 4
4. ADJUSTMENT .............................................................................................. 6
(1) Adjustment of the belt tension .................................................................................................. 6
(2) Adjustment of the needle stop position .................................................................................... 8
1) How to sdjust the upper stop position (after thread trimming) .................................................. 8
2) How to sdjust the lower stop position........................................................................................ 8
(3) Adjustment of the wiper (WB type) ........................................................................................ 10
(4) Theory of thread trimming ...................................................................................................... 12
(5) Thread trimming sequence .................................................................................................... 13
(6) Adjustment of the timing of the thread trimmer cam .............................................................. 14
1) How to adjust the timing ........................................................................................................ 14
2) How to adjust the timing of the thread trimmer cam .............................................................. 14
(7) Adjustment of the position of the moving knife........................................................................ 16
1) Proper position of the moving knife ........................................................................................ 16
2) How to position the moving knife .......................................................................................... 16
3) When the moving knife can not be properly positioned merely by adjusting
the position of the link driving magnet pin .............................................................................. 16
(8) Adjustment of the counter knife .............................................................................................. 18
1) Properly installing the knife thread guide .............................................................................. 18
2) Adjusting the counter knife .................................................................................................... 18
(9) Adjustment of the floating amount of the tension disc No. 2 .................................................. 20
1) How to check the floating amount of the tension disc No. 2 .................................................. 20
2) How to adjust the floating amount of the tension disc No. 2 .................................................. 20
(10) Sharpening the counter knife ................................................................................................ 22
(11) Replacing the moving knife .................................................................................................... 24
(12) Replacing the knife thread guide ............................................................................................ 26
(13) Adjustment of the thread take-up picker ................................................................................ 28
1) Positioning the thread take-up picker...................................................................................... 28
2) How to adjust the position of the thread take-up picker .......................................................... 28
(14) Adjustment of the clutch disc and thread trimmer solenoid .................................................... 30
(15) Adjustment of driving arm stopper .......................................................................................... 32
(16) Adjustment of the knife mounting base .................................................................................. 34
(17) Adjustment of the one-touch type reverse feed switch lever .................................................. 36
(18) How to replace the synchronizer ............................................................................................ 38
(19) Adjustment of normal/reverse stitching .................................................................................. 40
(20) Setting and Ajusting for SC-920.............................................................................................. 42
1) Setting procedure of the machine head .................................................................................. 42
2) Machine head list .................................................................................................................... 43
5. TROUBLES AND CORRECTIVE MEASURES .......................................... 44
(1) Mechanical components ........................................................................................................ 44
(2) Sewing performance .............................................................................................................. 50
6. BOBBIN CASE WITH AN IDLING PREVENTION SPRING ...................... 61
(1) How to adjust the tension of the an idling prevention spring .................................................. 61
(2) When using a bobbin case...................................................................................................... 61
(3) How to correct irregular stitches produced at high/low speed ................................................ 61
7. BRIEFLY CHECKING THE ADJUSTMENT
OF THE THREAD TRIMMER OF DDL-8700-7 SERIES ............................ 62
8. DRAWING OF THE TABLE ...................................................................... 64
1. GENERAL
(1) Features
1. The sewing speed can be changed continuously from low to high by adjusting the level of depression
of the pedal, contributing to higher efficiency.
2. Performs automatic reverse feed stitching at the start and end of sewing.
When the front part of the pedal is depressed, the machine carries out reverse feed stitching at
constant speed, assuring consistent quality.
3. The pressure required for depressing the front and back parts of the pedal can be adjusted to suit
each operator.
4. A operation panel mounted on the machine head enables the operator to easily check ON/OFF of
the main switch and automatic reverse stitch at start/end, and stitching patterns selected. This
feature virtually eliminates chances for operational mistakes.
5. A synchronizer is included in the handwheel to ensure easy operation.
(2) Applications
1. Standard models
Extensively used for light- to medium-weight general fabrics in men’s suits, Iadies’wear, working wear,
student’s uniforms, etc. Cotton or synthetic thread of #80 to #30 is generally used.
2. NA-type machines for light-weight materials
Suited for relatively light-weight materials from tetoron broadcloth to silky materials and georgette in
men’s shirts, blouses, etc. Cotton or synthetic thread of #80 to #50 is mainly used for these models.
Needle
DB × 1
DB × 1 KN
DA × 1
Size
Thread
#9
#80
#11
Materials
Application
Georgette, nylon, T/C broadcloth
Extremely light-weight materials
#80 ~ #60
General broadcloth, light-weight knit
Light-weight materials
#14
#60 ~ #50
Wool, cotton gaberdine, drill
General fabrics
#16
#50 ~ #30
Overcoats
Medium-weight materials
#18
#30 ~ #20
Denim
Heavy-weight materials
#9
#80
Georgette, nylon, T/C broadcloth
Extremely light-weight materials
#10
#60
General broadcloth, Iight-weight knit
Light-weight materials
#12
#50
Wool cotton gaberdine, drill
General fabrics
#8 ~ #9
#80
Georgette, nylon, T/C broadcloth
Extremely light-weight materials
#11
#60
General velvet, Iight-weight knit
Light-weight materials
#14
#50
Wool, cotton gaberdine, drill
General fabrics
−1−
2. SPECIFICATIONS
Model
DDL-8700-7
Standard
DDL-8700A-7
Light-weight
DDL-8700H-7
Heavy-weight
4,000 sti/m
4,000 sti/m
Cotton thread Synthetic thread
1
Max. sewing speed
2
Max. stitch length
3
Needle bar stroke
4
Needle (standard)
5,000 sti/m
4,000 sti/m
4 mm
30.7 mm
5 mm
29 mm
DB × 1
#9 to #18
DB × 1 #14
DA × 1 #9
DB × 1 KN
#9 to #18
DA × 1
#9 to #11
35 mm
DB × 1 #21
5
Presser foot pressure
6
lift of presser foot
7
Presser foot
8
Feed dog
9
Height of feed dog
10
Feed system
11
Thread take-up
12
Thread take-up stroke
13
Lubrication
14
Oil return
By plunger pump
15
Lubricant
JUKI NEW DEFRIX OIL No.1 or
JUKI MACHINE OIL 7 (equivalent to ISO VG7)
16
Wiper
17
Automatic reverse
stitching device
18
Motor
Compact-size servo motor M92 (450W)
19
Motor output
Related output 400 W, Max. output 550 W
4 to 5 kg
4 to 5 kg
5 to 7 kg
By hand : 5.5 mm
By knee : 13 mm
By hand : 4 mm
By knee : 9 mm
By hand : 5.5 mm
By knee : 13 mm
Exclusive hinging presser foot
4-row teeth or 3-row teeth
(feed dog tilt adjustable)
4-row teeth
(feed dog tilt adjustable)
4-row teeth
(feed dog tilt adjustable)
0.75 to 0.85 mm
0.7 to 0.8 mm
1.0 mm
Swing type
Link-type
Standard 107 mm
(Max.112 mm to Min.105 mm)
Max.115 mm to Min.108 mm
Fully automatic
Equipped (WB)
Equipped (WB)
Not equipped
Equipped as standard device
Control box
Power supply
DB × 1
#19 to #23
SC-920
Single-phase 100 to 120 V, 3-phase 200 to 240 V, Single-phase 220 to 240 V
20
Frequency
50 Hz / 60 Hz
Power consumption
320 VA
21
Solenoid drive power supply
DC24 V
22
Max. speed adjustment range
400 sti/min, to max. speed
23
Needle up/down
stop selector switch
24
Auto-lifter
25
Machine head weight
The machine normally stops with its needle down.
By setting this switch, the machine can be stopped with its needle up.
Option (AK85)
30 kg
−2−
MEMO
−3−
3. NAME OF EACH COMPONENT
❹
❷
❾
❸
❽
❶
❻
❺
❼
/ Power switch
6 Motor (M 92)
4 Operation panel (CP-18, CP-180)
2 Pedal
) Synchronizer
* One-touch type reverse feed switch
0 L-shaped thread stand
- Wiper
1 PSC box (SC-920)
Adjusting screw for levelling the stand or caster
−4−
❶ Power switch
Power switch of the motor, PSC and operation panel.
❷ Operation panel (CP-18, CP-180)
Automatic reverse feed stitching, the stitch number of pattern sewing, etc. are set through this operation
panel.
❸ Synchronizer
Built inside the sewing machine pulley and used to detect the upper and lower positions of the needle
and transmit input signal to the PSC box.
❹ L-shaped thread stand
❺ PSC box (SC-920)
Comprises a circuit to control the sewing machine and motor, an output circuit to operate the elements
(thread trimming solenoid, reverse feed solenoid, etc.), a pedal sensor to sense pedal operation, and a
power circuit to actuate the elements.
❻ Motor (M92)
Operates the machine at high speed medium speed low speed in response to the signals received from
the PSC box.
❼ Pedal
The front and back parts of the pedal are depressed to control the sewing speed and to actuate the
thread trimmer, presser foot lifter (AK85 type only), etc.
❽ One-touch type reverse feed switch
Used by hand to perform reverse feed stitching.
❾ Wiper
Wipes out the needle thread after thread trimming in response to the wiper signal received from the PSC
box.
Adjusting screw for levelling the stand or caster
Used to perform adjustment so that the table stands on the floor flatly to minimize variable during
operation.
−5−
4. ADJUSTMENT
(1) Adjustment of the belt tension
Standard adjustment
belt
❶
−6−
Adjustment Procedure
Results of Improper Adjustment
1. To avoid such problems, use a belt of an appropriate length as
specified in the INSTRUCTION MANUAL.
2. Adjust the belt tension using nut ❶ so that the middle of the
belt slacks about 18 mm when a 9.8N (1kgf) pressure is
applied.
c An excessive belt tension may
damage the main shaft bushing
of the machine or the motor
bearing.
c An insufficient belt tension may
cause the belt to slip with
consequent shortened life of the
belt, and also cause other failures
such as overrun after thread
trimming and machine stops with
uneven needle stop height.
−7−
(2) Adjustment of the needle stop position
Standard adjustment
1) How to sdjust the upper stop position (after thread trimming)
Hand wheel
❶
2) How to sdjust the lower stop position
❷
❸
−8−
Adjustment Procedure
Results of Improper Adjustment
1) How to adjust the upper stop position (after thread triming)
1. The standard upper needle stop position is such that the
marker
dot on the arm aligns with the white marker
dot
on the handwheel when the needle ❸ stops after thread
trimming.
2. With the needle ❸ in its upper stop position, loosen screw ❶
shown in the figure at right to perform adjustment within the
slit.
o Move toward
to advance stop timing.
o Move toward
to retard stop timing.
(Caution) Do not the machine with screws ❶ loosened while
making the above adjustment. Screws ❶ should
be loosened only, and should not be removed.
2) How to adjust the lower stop position
1. To adjust the lower stop position of the needle ❸ at the time
when the pedal is set to the neutral position after the front part
of the pedal is depressed, set the needle ❸ in its lower stop
position, and loosen screw ❷ to make adjustment within the
slit.
o Move toward
to advance stop timing.
o Move toward
to retard stop timing.
(Caution) Do not run the machine with screws ❷ loosened
while making the above adjustment. Screws ❷
should be loosened only, and should not be
removed.
−9−
(3) Adjustment of the wiper (WB type)
Standard adjustment
1) Adjusting the position of the wiper
❶
❷
❸
2mm
❹
❻
1mm
❺
− 10 −
Adjustment Procedure
Results of Improper Adjustment
Adjust the position of the wiper according to the thickness of
materials to be sewn as follows:
1. Turn the handwheel in the normal rotational direction to align
white dot ❶ on the handwheel with dot ❷ on the machine arm.
2. Insert wiper ❻ into wiper collar ❹ until the vertical clearance
between the wiper edge and the needle point is 2 mm, and
until the parallel clearance between the needle center and the
straight inside face of the wiper is 1 mm.
Press wiper collar ❹ against wiper ❻, and securely tighten
wiper adjustment screw ❸.
(Caution) Do not loosen the wiper solenoid setscrew.
When the wiper ❻ is not used, turn the wiper
seesaw switch ❺ OFF.
− 11 −
(4) Theory of thread trimming
1) The blade point of the sewing hook catches the needle thread.
2) The moving knife spreads the threads. (goed back)
3) The moving knife hooks the needle and bobbin threads
(advances).
4) The threads are trimmed.
− 12 −
(5) Thread trimming sequence
Standard adjustment
The knife hooks
the threads.
Tension release
is terminated.
The knife spreads
the threads.
The front part
of the pedal
is trodden.
Low to high speed
The back part
of the pedal
is trodden.
Detection
The thread
trimming solenoid
is activated.
The cam
disengages
from the roller.
Power switch
“ON”
The needle
goes up.
Reverse feed
stitching at
the end.
The pedal is
set to the
neutral position.
Reverse feed
stitching at
the start.
The machine
stops with its
needle down.
The cam engages
with the roller.
The thread tension
is released.
The machine rotates
to cause the needle
to go up.
Threads are
trimmed.
The machine stops.
A needle-up
stop signal
ts given.
The thread trimming
solenoid is turned OFF.
(Caution) The above chart assumes that the switches for automatic reverse feed stitching
at the start and end have been set to “ON”.
− 13 −
(6) Adjustment of the timing of the thread trimmer cam
Standard adjustment
1) How to adjust the timing
❹
Turn the cam ❹
in this direction
by hand.
❺
❼ ❽
2) How to adjust the timing of the thread trimmer cam
❸
Marker dot ❶
❷
− 14 −
❻
Adjustment Procedure
Results of Improper Adjustment
1) How to adjust the timing
The timing of the thread trimmer cam ❹ for cotton and synthetic
threads can be obtained simply by aligning the marker dot on the
machine arm and the marker dot on the handwheel.
1. Tilt the machine head, manually turn the handwheel until the thread
take-up lever almost reaches its highest position, and press thread
take-up picker ❺ to the right by finger. This causes the cam roller ❻
to fit in the groove of the thread trimmer cam ❹. With this condition
maintained, turn the handwheel in the direction opposite to the
normal rotational direction, and you will find a position in which the
handwheel no longer turns. Then, adjust the cam timing so that
marker dot ❶ on the machine arm is aligned with red marker dot ❷
on handwheel as shown.
This provides the proper cam timing for cotton and synthetic threads.
2) How to adjust the timing of the thread trimmer cam
1. Loosen screw ❼ No.1 first, and then screw No.2, and align red
marker dot ❷ on the handwheel with red marker dot ❶ on the
machine arm.
2. Fit the cam roller ❻ in the groove of the trimmer cam ❹ while
pressing thread take-up picker ❺ to the right. Manually turn only the
trimmer cam ❹ (do not turn the hook driving shaft) in the direction
opposite from the normal rotation of the hook driving shaft (see the
arrow in) until a position in which the cam goes no further is reached.
In this position, press the trimmer cam ❹ against the thrust collar ❻
of the thread trimmer cam ❹, and retighten the screw ❼ No.2 first
and then the screw No.1.
3. If the cam collar ❽ has not been moved, press the thread trimmer
cam ❹ against the cam collar ❽, and retighten the screw No.2 first
and then the screw No.1.
(Ref.) 1. The red marker dots ❷ engraved on the handwheel provide
the standard cam timings. It is possible to obtain a timing
which is approx. 2 ° earlier than that for cotton or synthetic
thread, or a timing which is approx. 5° later than that for cotton
or synthetic thread. In this case, however, confirm that the
moving knife securely separates the two threads below the
throat plate bottom surface. If a cam timing is tod to slip or too
late, the thread remaining on the needle may become too
short, causing the needle threa)ove of off the needle
immediately after thread trimming. Also, the cam roller ❻
may fail to fit in the groove of the thread trimmer cam ❹.
2. The thread trimmer cam timings for cotton and synthetic
threads are basically the same. However, if the following
problems are presented when using a thinner synthetic thread:
(1) A few beginning stitches are skipped.
(2) Thread slips off the needle at the start of sewing.
Perform the following adjustment for special synthetic
threads: (of a small number count)
(3) Align marker dot ❶ on the machine arm with green marker
dot ❸ on the handwheel.
(4) Use the soft start (800sti/min) function for the first starting
stitch.
(Caution) Adjustment (3) is not applicable for a thread with
a large number count.
− 15 −
(7) Adjustment of the position of the moving knife
Standard adjustment
1) Proper position of the moving knife
2) How to position the moving knife
3) When the moving knife can not be properly positioned merely by adjusting the position of the
link driving magnet pin
V-slit used for
adjusting the
position of the
moving knife
m
m .7)
0.5 to 0
.2
(0
0
3.5 mm _ 0.5
❽
Center of needle
Most retreated position
Home position
❼
❾
❺
❻
❹
❷
❸
❶
❽
− 16 −
Adjustment Procedure
Results of Improper Adjustment
1) Proper position of the moving knife
1. The correct position of the moving knife ❽ when the moving knife
has gone back farthest is such that the tip of the moving knife is 3 to
3.5 mm away from the center of the needle. If the retreat of the
moving knife ❽ is not enough, the knife may fail to catch the needle
or bobbin thread at the time of thread trimming. On the contrary, if
the moving knife ❽ retreats excessively, the moving knife ❽ may hit
the feed dog.
2. To avoid these problems, be sure to accurately position the moving
knife ❽.
The standard moving knife home position is obtained by bringing the
periphery of the moving knife ❽ in contact with the V groove of the
knife monting base.
2) How to position the moving knife
The position of the moving knife is adjusted by changing the lateral
position of moving knife link pin ❶ while the machine is at rest.
1. Loosen the lock nut of moving knife link pin ❶.
2. Move the link driving magnet pin ❶ to the right or left to make the V
groove ❸ meet the periphery of the moving knife ❽, referring to the
home position.
3. Retighten the lock nut of the moving knife link pin ❶ when the proper
position of the moving knife has been obtained. As the moving knife
link pin ❶ is moved to the right, the retreat of the moving knife
increases. As it is moved to the left, the retreat of the moving knife
decreases.
3) When the moving knife can not be properly positioned merely
by adjusting the position of the link driving magnet pin
1. Loosen adjusting nut of moving knife link pin ❶.
2. Adjust so that the center of the moving knife link pin ❶ aligns with V
groove ❸ of the knife driving arm ❷, and fix link driving magnet pin
by tightening the lock nut.
3. Loosen two screws ❺ of the knife driving arm stopper ❹.
4. Move the knife driving arm ❷ to make the periphery of the moving
knife meet the V groove of the mounting base, and fix knife driving
shaft stopper ❹ by tightenjng two screws ❺.
5. Loosen the two screws of thread trimmer cam ❼ and cam collar ❻.
6. Align red dot on the handwheel with red dot ❶ on the machine arm.
7. Manually turn the cam until screw ❾ faces toward you.
Then press the thread take-up picker
to the right.
8. Move the trimmer cam ❼ to the right or left to engage the trimmer
cam ❼ with the cam roller.
9. With the trimmer cam ❼ engaged with the cam roller, turn the
trimmer cam ❼ in the direction of the arrow toward you until it stops,
while lightly pulling the trimmer cam ❼ to the right.
10. Tighten screw ❾ of the trimmer cam ❼ for preliminary installation.
11. Then confirm :
(1) that the specified marker dots on the machine arm and handwheel
are in alignment,
(2) the roller smoothly fits in the cam groove, and
(3) the retreat of the knife has been set to 3 to 3.5 mm.
12. Securely tighten the two screws of the cam.
13. Press the cam collar ❻ against the trimmer cam ❼ and fix it by
tightening the screw.
(Caution) 1. Note that a minute change in the lateral position of the
moving knife link pin ❶ will greatly affect the retreat
of the knife.
2. Confirm that the moving knife ❽ spreads the threads
as shown.
− 17 −
(8) Adjustment of the counter knife
Standard adjustment
1) Properly installing the knife thread guide
2) Adjusting the counter knife
Bottom face of
throat plate (bed)
❸
❶
Center of needle
x.
o
pr m
ap 4 m
5
0.
m
❷
m
Short Long
Length of thread remaining on needle
❷
0.6 mm
When counter knife ❷ is
moved to right
Center
Standard
❸
❷
❸
Hook
− 18 −
Thread take-up picker
Adjustment Procedure
Results of Improper Adjustment
1) Properly installing the knife thread guide
Install the knife thread guide ❶ so that the needle enters exactly
the center of its opening.
2) Adjusting the counter knife
1. The standard distance from the blade point of the counter knife
❷ to the knife thread guide ❶, which is positioned so that the
needle enters the center of its opening, is 0.5 mm.
2. The blade point of the counter knife ❷ is about 4 mm away from
the center of the needle.
3. The blade point of the counter knife ❷ is located 0.6 mm above
the installing surface.
4. The sharpness of the counter knife ❷ depends upon the
installing angle of the blade tip of the counter knife ❷.
The proper overlap of the counter knife ❷ blade with that of the
moving knife ❸ will provide the best sharpness.
5. Whenever the counter knife ❷ has been readjusted or
replaced, be sure to check the sharpness of the counter knife
❷, and adjust the installing angle of the counter knife ❷.
6. The installing position of the counter knife ❷ can be moved to
the right from the standard position.
When the counter knife has been installed in such a position,
the needle and bobbin threads to be pulled out become
correspondingly longer, and also the timing of thread trimming
is delayed, resulting in an increased length of the thread
remaining on the needle after thread trimming.
When using synthetic thread, the timing of thread trimming can
be delayed by moving the counter knife ❷ to the right.
In this case, the timing of the thread trimmer cam must also be
adjusted. Refer to 4.-(6) Adjustment of the timing of the thread
trimmer cam.
− 19 −
(9) Adjustment of the floating amount of the tension disc No. 2
Standard adjustment
1) How to check the floating amount of the tension disc No. 2
Thread trimmer cam
Turn the cam in this
direction by hand.
❸
Screw No.2
Cam collar
Roller
❹
2) How to adjust the floating amount of the tension disc No. 2
❷
❶
− 20 −
Adjustment Procedure
Results of Improper Adjustment
1) How to check the floating amount of the tension disc No. 2
Check whether the tension disc No. 2 ❹ floats 0.5 to 1 mm when
thread take-up picker ❸ is pressed to the right with the thread
take-up lever located slightly below its highest position and the
presser foot lifted.
2) How to adjust the floating amount of the tension disc No. 2
1. To increase the floating amount, loosen screw ❶, and move
tension release wire ❷ to the right.
2. To decrease the floating amount, loosen screw ❶, and move
tension release wire ❷ to the left. After adjustment, securely
tighten screw ❶.
− 21 −
(10) Sharpening the counter knife
Standard adjustment
Sharpen this point well
Sharpen this face (A face)
Blade point (B face)
❶
❶
❷
D
C
C and D of moving knife ❷ must come in contact with
counter knife ❶ at the same time.
❶
− 22 −
Adjustment Procedure
Results of Improper Adjustment
1. The most important factor of the sharpness of the thread
trimmer is the shape of the blade tip of the counter knife ❶.
2. In most cases, the sharpness of the thread trimmer can be
improved by mere]y sharpening the blade of the counter knife
❶.
(Caution) For proper thread trimming, the blade of the
counter knife ❶ must be brought into contact
with the blade of the moving knife ❷.
(1) The sharpness of the thread trimmer is improved simply by
sharpening “A” (Pay attention to the angle).
(2) The thread trimmer also becomes dull when “B” is worn
and rounded. Take care not to change the angle when
sharpening the blade edge.
(Ref.) 1. The contact of the moving knife ❷ with the counter
knife ❶ can also be improved by changing the angle
shown by the arrow.
2. When “D” side is dull, decrease this angle.
When “C” side is dull, increase the angle.
− 23 −
c If the thread trimmer is still dull
even after the blade of the
counter knife ❶ has been
sufficiently sharpened, it is
because the two points of the
moving knife ❷ fail to contact
with the blade of the counter
knife ❶ at the same time.
In this case, correct the tilt of the
counter knife ❶.
(11) Replacing the moving knife
Standard adjustment
❶
❷
❸
❹
❻
❺
− 24 −
Adjustment Procedure
Results of Improper Adjustment
Remove the moving knife in the following order:
1. Loosen screw ❺.
2. Remove hinge screw ❸ using 3 mm Hex-head stick Spanner
❹.
3. Remove forked hinge screw ❶. Lift forked base ❷ for knife,
and remove the moving knife pin from the forked base ❷ for
knife.
4. After removing the moving knife pin, slide the moving knife to
the left, and remove it from the bottom face of the forked base
❷ for knife.
5. Assemble the moving knife unit by reversing the above order.
6. After tightening the hinge screw ❸ of the moving knife, move
the moving knife by hand to confirm that it moves smoothly
without play.
7. Securely insert the pin for knife forked base into the forked
base ❷ for knife.
8. Tighten the forked hinge screw ❶.
9. Install and tighten the hinge screw ❺ of the moving knife link.
10. Confirm that the knife is actuated when moving knife link ❻ is
moved to the right and left.
− 25 −
c Prior to taking actions for
re-assembly, apply an appropriate
grease to the hinge screw ❺ of
the moving knife link.
Appropriate grease part No:
40006323
(12) Replacing the knife thread guide
Standard adjustment
Bottom face of
throat plate (bed)
Moving knife
❹
Center of needle
x.
o
pr m
ap 4 m
5
0.
m
❺
m
❸
❷
❶
Short Long
Length of thread remaining on needle
− 26 −
Adjustment Procedure
Results of Improper Adjustment
1. Change the knife thread guide ❹ by loosening screws ❷ and
❸, with screw ❶ left tightened.
2. The installing angle of the counter knife ❺ has been disturbed,
readjust it in accordance with 4-(8). “Adjustment of the counter
knife”.
If there is no coincidence of the
c
− 27 −
knife thread guide ❹ and the
center the needle, this can be a
cause of balloon stitches.
(13) Adjustment of the thread take-up picker
Standard adjustment
1) Positioning the thread take-up picker
2) How to adjust the position of the thread take-up picker
Thread triming unit
Cloth link
Marker line
❸
Picker link
❷
❶
❹
Picker arm
Positioning the thread take-up picker ❸ :
When the thread take-up pickers touched the
bobbin, adjust so that the end of the thread
take-up picker ❸ is aligned with the right
end of the marker line.
❸
❸
1.0 to 1.5 mm
❸
Bobbin
− 28 −
Adjustment Procedure
Results of Improper Adjustment
1) Positioning the thread take-up picker
1. With clutch disc ❶ pushed in the direction of arrow (to the
right), make adjustment so that the bobbin thread can be
pulled out smoothly.
2. The adjustment so that a clearance of 1.0 to 1.5 mm is
provided between the tip of the thread take-up picker ❸
(bobbin winder trip latch) and the middle of the top recess of
the bobbin case, and also the rear end of the bobbin winder
trip latch is aligned with the marker line of the thread take-up
picker ❸.
c If thread take-up picker ❸ enters
2) How to adjust the position of the thread take-up picker
1. After loosening screws ❹, adjust so that the tip of the thread
take-up picker ❸ (bobbin winder trip latch) is positioned, and
tighter setscrews ❹.
2. To adjust the entrance of the thread take-up picker ❸ into the
bobbin case, picker link pin ❷.
3. After completion ofthe above adjustment, retighten the nut of
the picker link pin ❷.
4. The standard position of the picker link pin ❷ is such that, with
the clutch disc ❶ pushed to the right, the end of the picker ❸
is the right side with marker line.
− 29 −
the bobbin case too deeply at
the time of thread trimming, the
bobbin does not turn, and the
bobbin thread is cut too short,
causing stitch skipping at the
start of sewing.
cOn the contrary, if the entrance
of the thread take-up picker ❸
into the bobbin case is not
enough, the needle thread slips
off the tip of the thread take-up
picker at the time of thread
trimming.
As a result, the thread remaining
on the needle after trimming
becomes too short, causing the
thread to slip off the needle.
(14) Adjustment of the clutch disc and thread trimmer solenoid
Standard adjustment
❶
Thread trimmer solenoid stroke 6 mm
Thread trimming
cam
Roller arm Ass’y
A
❷
− 30 −
❶
❸
Adjustment Procedure
Results of Improper Adjustment
1. The thread trimmer solenoid ❶ stroke is 6 mm.
2. Position the clutch disc ❷ and trimmer solenoid ❶ so that,
when the thread trimmer solenoid ❶ is actuated, clearance A
becomes 0.1 mm to 0.5 mm.
3. Then tighten setscrews ❸.
− 31 −
(15) Adjustment of driving arm stopper
Standard adjustment
❶
❷
❹
❻
❹
A
❸
Needle
❺
❺
Needle entry
− 32 −
Adjustment Procedure
Results of Improper Adjustment
1. Press the roller arm ❸ in the direction of arrow A until it is
pressed against the stopper ❻ of the driving arm stopper ❹.
2. At this time, adjust screw ❶ and ❷ so that the stopper ❻
works at a position where the moving knife ❺ does not reach
the needle entry.
− 33 −
(16) Adjustment of the knife mounting base
Standard adjustment
❺
❻
❶
❷
❼
❸
❹
− 34 −
❽
Adjustment Procedure
Results of Improper Adjustment
Removing knife mounting base ❶ in the following sequence:
1. Remove the hook.
2. Remove the hinge screw ❷ of the picker link ❻, and take out
the hinge screw ❸ of the picker arm ❼.
3. Remove hinge screws ❹ and ❺, then, the knife mounting
base ❶ can be remove.
* To install the knife mounting base, reverse the above sequence.
− 35 −
(17) Adjustment of the one-touch type reverse feed switch lever
Standard adjustment
❶
❷
− 36 −
Adjustment Procedure
Results of Improper Adjustment
1. There is no specified height for one touch reverse feed switch
lever ❶, and therefore the one-touch type reverse feed switch
lever may be positioned at any height suited for each operator.
2. Loosen screw ❷ and move the switch lever ❶ up and down to
obtain a suitable height.
Retighten the screw ❷ after adjustment.
(Caution) This switch is sometimes abbreviated to “B.T.SW”
(Back tack switch).
− 37 −
(18) How to replace the synchronizer
Standard adjustment
❶
❷
❸
1 ± 0.2 mm
Hand wheel
Stator mounting base Ass’ y
− 38 −
Adjustment Procedure
Results of Improper Adjustment
If the synchronizer fails, the needle will not stop in the upper or
lower position when the machine stops, causing the safety circuit
to be put into operation, or the machine will keep on running at
high speed when it should stop.
Replace a faulty synchronizer in the following sequence. Note
that the synchronizer is always changed together with the pulley.
1. Removing the belt cover, Ioosen two setscrews ❶ of the pulley
to remove the pulley.
2. Remove the cord setscrew ❸ and two setscrews ❷ of the
stator mounting base to remove the stator.
3. Fix a new stator by the two setscrews ❷.
4. The stator mounting base is made of plastics. Tighten the
setscrews ❸ with approx. 1.47 N.m torque.
5. Retighten the cord setscrew ❸.
6. Install the pulley so that the screw No. 1 contacts the flat part
of the main shaft, and a 1 mm ± 0.2 mm clearance is provided
between the stator mounting base and the end face of the
pulley as shown in the figure.
7. Turn the pulley by hand to check it for smooth rotation.
8. Install the cord, and attach the V belt to the pulley.
Then confirm that there is no contact between the V belt and
the cord.
9. With the needle set in the lower position, turn on the power
switch. The machine will then operate until the needle has
gone up fully. If the needle stop position at that time is
considerably deviated from the standard, check the position of
the pulley two setscrews ❶.
10. Run the machine at low speed to check for any frictional
noise. After reinstalling the belt cover, check for frictional
noise again.
11. Adjust the upper and lower needle stop positions by the two
setscrews of the magnet mounting base of the pulley. (Refer
to 4.-(2) Ajusting the needle stop position)
− 39 −
(19) Adjustment of normal/reverse stitching
Standard adjustment
❶
❷
❸
− 40 −
Adjustment Procedure
Results of Improper Adjustment
1. Pinch a piece of paper beneath the presser hardware and set
the feed dial graduation at 3.
2. Remove the window plate on the sewing machine.
3. Loosen two feed adjust pin setscrews ❶ and make normal/reverse
adjustments by turning the feed adjust pin ❷.
4. By turning the flywheel by hand in forward direction, confirm
that the normal and reverse pitches coincide with each other.
5. When coincidence is confirmed, tighten the two feed adjust pin
setscrews ❶.
c When the normal and reverse
pitches are net same, the return
stitches are in appropriate.
cThe chamfered section ❸ of the
feed adjust pin ❷ should be
adjusted on the window plate.
cUnder the condition that the feed
adjust pin ❷ is pressed, tighten
the two feed adjust pin setscrews
❶. Pay attention so that there is
no presence of thrust rattling.
− 41 −
(20) Setting and Ajusting for SC-920
1) Setting procedure of the machine head
(Caution) For the operation panel other than CP-18, refer to the Instruction Manual for the operation
panel to be used for the setting procedure of the machine head.
1. Refer to "Ⅲ-(6) Setting for functions
of SC-920 Instruction Manual", and
call the function setting No. 95.
❸
❹
❺
❻
2. The type of machine head can be
selected by pressing
(
switch ❺
switch ❻).
* Refer to "CAUTIONS WHEN SETTING UP THE SEWING MACHINE"
or "Machine head list" on the separate sheet for the types of machine
heads.
❸
❹
❺
❻
3. After selecting the type of machine
head, by pressing
(
switch ❸
switch ❹), the step proceeds to
96 or 94, and the display automatically changes to the contents of the
setting corresponding with the type
of machine head.
❸
❹
❺
❻
− 42 −
2) Machine head list
No.
∗
Machine head
Type
Contents of display Number of revolutions at
the time of delivery (sti/min)
Max. number of
revolutions (sti/min)
1
DDL-9000B MA/MS/SS
dLbM
4000
5000
2
DDL-9000B DS
dLbd
4000
4000
3
DDL-9000B SH
dLbH
4000
4500
4
DDL-9000A MA/MS/SS
dLAM
4000
5000
5
DDL-9000A DS
dLAd
4000
4000
6
DDL-9000A SH
dLAH
4000
4500
7
LH-3528/68A
H35d
3000
3000
8
DLN-9010
Ln9S
4000
5000
9
DDL-8700
dL87
4000
5000
10
DDL-5600J
dL6J
4000
4000
11
DDL-5600L,U,R
dL6L
3000
3000
12
DDL-5550
dL50
4000
5000
13
DLU-5490
LU90
4000
4500
14
DLD-5430
Ld54
4000
4500
15
DLN-5410
Ln54
4000
5000
16
DLM-5400
LM54
4000
4500
17
LZ-2280
Z280
4000
5000
∗Machine head set at the time of delivery
(Caution) 1. When the dry-type machine head is connected, any model other than dry-type one
cannot be set.
2. Refer to the machine head list (40088647) for the details of each machine head.
− 43 −
− 44 −
Cause (1)
Check “a” and “b” of the presser foot, and “A” of the throat plate.
c When synthetic thread is used for tricot “a”< 0.8 mm, and radius of
“A” and “b”< 0.3 mm.
c When synthetic thread is used, “a” shall be smaller than 1.2 mm,
and there shall be no relief at “b” and “A”.
c For cotton thread, the relief at “a”, “b” and “A” should be
minimized as long as good tightness of stitches is obtained.
c The smaller the relief at “a”, “b”, and “A”, the better for
lighter-weight or coarser fabrics, more slippery thread, or smaller
stitch length.
2)-A The presser foot can not hold the needle
thread because “a” dimension of the
relief at “b” of the presser foot is too
large.
To the next page
b
Correct the timing for a synthetic thread (special)
1)-H The standard cam timing is too early.
a
Check the hole of the knife thread guide and hook for scratches or burrs,
and if a scratch or burr has been found, buff it. If buffing does not
correct the trouble, replace the components.
1)-G The knife thread guide, moving knife,
or hook has a flaw.
Check and correct the cam timing in accordance with 3-6.
1)-D The timing of the tread trimming cam is
too early.
Removing the throat plate, check and correct the position of the counter
knife, or check for any scratch on the moving knife (Refer to 4-(8)).
Check whether the floating amount of the 2nd thread tension disk reads
between 0.5 and 1 mm when the hook thread presser is pushed into until
the tip of the presser reaches the bobbin. The floating amount is
adjustable by moving the tension release wire on the underside of the
bed. Check whether the disk is horizontally loosened. If not, turn the
thread tension spring 180 degrees or correct the spring inclination.
1)-C The floating amount of the 2nd thread
tension disk is insufficient at thread
trimming.
1)-F The counter knife is too close to the
needle, or the knife tip is too sharp.
Turn the thread tension nut of the 1st thread tension disk
counterclockwise to decrease the tension.
1)-B The tension of the 1st thread tension
disk is too high.
Check for loosened setscrew of the thread take-up picker.
Check the needle thread path. Remove thread entangled with thread
guide pin, or correct the position of the thread guide on the thread stand
or other troubles.
1)-A Something is wrong with the needle
threat route and the needle thread
tension is too high at thread trimming.
1)-E The needle thread is detached at thread
trimming due to wrong position of the
hook thread presser.
Check and corrective measures
Cause (2)
To the next page
1-2) An inappropriate needle,
throat plate, or presser is used.
Alternatively, the pressure of
the presser is too low.
1-1) The needle thread passing
through the needle is too short
after thread trimming.
To the next page
1. Skipping of one or more
stitches occurs at the start
of sewing.
Trouble
(1) Mechanical components
5. TROUBLES AND CORRECTIVE MEASURES
− 45 −
Trouble
1-5) Knot tying between the needle
and bobbin threads is not easy
at sewing start.
1-4) The bobbin thread is too short
at sewing start.
Cause (2)
From the previous page
Increase the pressure of the presser foot, with care taken not to cause the
feed power to decrease or stitches to jam.
Check the needle bar height, and align it with the ruled line on the
needle bar. For sewing knitted cloth, lower the needle bar slightly to
delay the timing.
Decrease the tension and momentum (Standard 5 to 7 mm).
Reshape the blade top or replace the hook.
Adjust the needle inclination, or replace the needle if the current needle
is bent.
2)-E The presser foot pressure is insufficient.
3)-A The timing between the needle and
hook is inappropriate.
3)-B The tension and momentum of the
thread take-up spring are too high.
3)-C The blade top of the hook is worn out.
3)-D The needle is inappropriately mounted.
Reduce the pressure of the bobbin presser.
However, be careful not to idle the bobbin.
Repair the flaw on the hook, or replace the hook.
Conduct 1 or 2 stitches of soft-start (800 sti/min) at the sewing start.
4)-B The pressure of the bobbin presser is
too high.
4)-C A flaw on the hook causes the bobbin
thread to be cut too short.
5)-A The sewing speed at sewing start is too
fast to knot the needle and bobbin
threads together.
Increase the bobbin thread tension.
Increase the pressure of the bobbin presser.
Replace the throat plate by one with a smaller needle hole.
2)-D The needle hole in the throat plate is too
large.
4)-A Bobbin idling pulls the edge of the
bobbin thread into the bobbin case.
A thinner needle is better as long as sufficient tightness of stitches is
obtained.
Check and corrective measures
2)-C The needle is too thick.
A
2)-B The relief at “A” of the throat plate
needle hole is too large.
From the previous page
1-3) The blade top of the hook
does not scoop the needle.
(stitch skipping)
From the previous page
Cause (1)
− 46 −
Refer to the previous item, [The needle thread passing through the
needle is too long after thread trimming].
Refer to the previous item, [An inappropriate needle, throat plate, or
presser is used. Alternatively, the pressure of the presser is too low].
Turn off the power, push the hook thread presser into the bobbin case by
hand when the needle reaches the lowest point, trim the needle while
turning the hand wheel, and stop the hand wheel when the thread
take-up lever comes to the upper dead point.
If the length of the needle thread passing through the needle at this
moment is 10 mm or more shorter than that of the pedal operation,
hasten the timing of thread trimming or decrease the 1st thread tension
because this is a midway cut.
Adjust the hook thread presser with reference to 4. -(13).
Re-sharpen the blade of the knife according to 4. -(10), or replace the
knife.
Remove the scratches or burrs, or replace the defective component.
Change the needle.
1)-A Refer to the previous item, [The needle
thread passing through the needle is too
long after thread trimming].
2)-A Refer to the previous item, [An
inappropriate needle, throat plate, or
presser is used. Alternatively, the
pressure of the presser is too low].
1)-A Too high 1st thread tension due to
delayed thread trimming timing causes
the thread to be cut before engagement
between the moving and counter
knives. (midway cut)
1)-B The thread take-up picker does not
enter the bobbin case sufficiently,
causing the needle thread to come off
the thread take-up picker from time to
time.
1)-C The blade of the counter knife has been
sharpened excessively, and thread is
trimmed only by the counter knife.
1)-D The knife thread guide, moving knife,
or hook has a flaw.
1)-E The needle is too thick.
3-1) The needle thread passing
through the needle is too long
after thread trimming.
3-2) Adjustment of the throat plate,
needle, or foot is
inappropriate, and the needle
thread passing through the
needle cannot be shortened
after thread trimming.
4-1) The length of the needle
thread passing through the
needle varies after thread
trimming.
To the next page
4. The needle thread slips off
the needle at the sewing
start.
Correct the position of the counter knife in accordance with 3-8.
1)-C The counter knife is set too back.
3. The underside of the
material is not neat at
sewing start.
(The needle thread remains
long under the material.)
Check and correct the cam timing in accordance with 3-6.
1)-B The timing of the tread trimming is too
late.
Check and corrective measures
Increase the 1st thread tension.
2-1) The needle thread passing
through the needle is too long
after thread trimming.
2. The edge of the needle
thread comes out on the
material at the sewing start.
Cause (2)
1)-A The 1st thread tension is too low.
Cause (1)
Trouble
− 47 −
6. The needle thread is
untrimmed. (But the
bobbin thread is trimmed.)
Adjust the hook thread presser with reference to 4. -(13).
1)-B Bobbin idling causes the bobbin thread
tension at sewing start to decrease.
6-2) The blade portion of the knife
is blunt.
6-1) Stitch skipping at the final
stitch occurs.
Adjust the hook thread presser with reference to 4. -(13).
1)-A The hook thread presser is
inappropriately mounted.
5-1) The tension of the needle
thread is too low at sewing
start.
Shorten the stroke of the thread take-up spring. (5 to 7 mm)
Check for stitch skipping at low sewing speed, and readjust the hook
timing (Adjust the hook timing 2.0 mm which is earlier than that for the
standard lockstitchers).
1)-B The stroke of the thread take-up spring
is too long.
1)-C The hook is inappropriately adjusted.
Correct the position of the
counter knife.
Correct the tilt of the blade tip
of the counter knife.
Sharpen the counter knife.
Mount a needle appropriately and make sure that the needle is not bent.
1)-A The needle is inappropriately mounted.
Remove the throat plate, and
manually operate the thread
trimmer to cut about three
cotton thread #50. When all the
three threads are cut evenly, no
further corrective action is
required. If not;
Refer to Cause (1) of 1-2).
1)-D The presser or throat plate is
inappropriate.
2)-A The blade portions of the moving and
counter knives are not per- featly
aligned at thread trimming.
(The mounting angle, position, and
blade inclination of the counter knife
are not matched with those of the
moving knife.)
Increase the tensions of the bobbin thread and needle thread.
1)-C The tensions of the bobbin thread and
needle thread are too low.
Use a spring loaded bobbin case.
Conduct 1 or 2 stitches of soft-start (800 sti/min) at the sewing start.
3)-A The sewing speed at sewing start is too
fast to knot the needle and bobbin
threads together.
4-3) Knot tying between the needle
and bobbin threads is not easy
at sewing start.
Check and corrective measures
Slipping of the needle thread from the needle immediately after thread
trimming results from cutting the needle thread passing though the
needle due to defective thread spreading by the moving knife. In such a
case, Thread chips of 40mm level exist under the throat plate or on the
under cover. In this case, delay the timing of the thread trimming cam.
Cause (2)
2)-A Too early cam timing or too late hook
timing causes the moving knife to cut
the needle thread to hold 3 threads
before thread separation.
Cause (1)
4-2) The needle thread slips off the
needle immediately after
thread trimming.
From the previous page
5. The thread tension is
inappropriate at sewing
start.
Trouble
− 48 −
To the next page
9-3) The thread trimming drive
unit does not function.
9-2) The thread is tense at thread
trimming.
9-1) The timings of the parts are
inappropriate.
9. The moving knife breaks.
3)-A The mounting position of the thread
trimming drive unit is inappropriate.
2)-B Hangnail of the thread is found.
Make an adjustment with reference to 4. -(15).
Check whether a gauge or a needle attached is suitable for the thread
(thick thread).
Buff the blade top of the hook or other thread paths if necessary after
checking them.
Check whether the timing and clearance of the hook are appropriately
adjusted.
Replace the needle with new one or a ballpoint needle if necessary after
checking the needle tip.
Loosen the tension release wire presser (bottom) and readjust the wire
position.
Adjust the timing of the disk floating with use of the setscrew of the
thread tension unit.
Make an adjustment with reference to 4. -(6).
1)-B The up stop position is inappropriate.
2)-A The thread tension disk does not float at
thread trimming.
Make an adjustment with reference to 4. -(6).
1)-A The timing of thread trimming is
inappropriate.
Mount the wiper appropriately.
Check whether the current hook has a guide slit for the bobbin thread.
If the hook has no such a slit, replace the hook with a hook for threat
trimming.
2)-A A hook other than the specified hook is
used.
7-2) The position of the bobbin
thread at thread trimming is
unstable.
8-1) The height of the position
where the wiper is mounted is
inappropriate.
Measure the backward movement length of the moving knife.
Adjust the position of the thread trimming cam in the right-left direction
to set the backward movement length of the knife to within 2.5 to 3 mm
(3 to 3.5 mm for SH) if the measurement result is out of the range.
1)-A The backward movement of the moving
knife is inappropriately adjusted. (The
position of the knife operation axis or
the thread trimming cam in the
right-left direction is inappropriately
adjusted.)
7-1) The backward movement of
the moving knife is
insufficient.
7. The bobbin thread is
untrimmed. (But the needle
thread is trimmed.)
8. The wiper interferes with
the needle. Trouble
Check and corrective measures
Cause (2)
Cause (1)
Trouble
− 49 −
Trouble
6)-A The cam roller is not disengaged from
the thread trimming cam groove in a
dwell section.
9-6) Thread trimming operates at
sewing start right after thread
trimming.
Adjust the position relation between the cam groove and roller.
Make an adjustment with reference to 4. -(8). (for engagement with the
counter knife)
Make an adjustment with reference to 4. -(7). (for backward movement
length of the moving knife)
Decrease the pressure so that the counter knife bites the moving knife
properly.
4)-B The knife pressure is excessive.
5)-A The thread is not trimmed.
Adjust the tension in accordance with 4. -(1).
Check and corrective measures
4)-A The tension of the timing belt is too low.
Cause (2)
9-5) The home position of the
moving knife is inappropriate.
9-4) The timing belt slips.
From the previous page
Cause (1)
− 50 −
Move the arm thread guide rightward to reduce the thread feeding with
the thread take-up lever.
Increase the stroke.
2)-D The stroke of the thread take-up lever is
too long.
2)-E The stroke of the thread take-up spring
is too short.
1-4) The material is
inappropriately stretched.
1-3) Pressing is inappropriate.
Delay the feed timing compared to the needle timing to reduce feeding.
2)-C The feed timing is too fast.
Use a presser with a smaller thread relief on the backside or without
thread relief.
Replace the presser foot or presser bar.
Replace the needle.
4)-B The thread relief on the backside of the
presser is too large.
4)-C The parallel level of the presser is
inappropriate.
4)-D The needle tip is blunt.
Use a fluorocarbon resin presser foot or nidax presser foot.
3)-C The material is difficult to feed.
Replace the current gauge with a new one having a smaller diameter
hole.
Use a buff or the like to smooth the presser.
3)-B The finish of the backside of the presser
is rough.
4)-A The needle hole of the throat plate is
too large.
Minimize the pressure as long as smooth material feed is assured.
3)-A The pressure is too high.
Use silicon.
Hasten the timing of the hook without occurrence of stitch skipping to
obtain smooth unthreading.
2)-B The timing of the hook is too late.
2)-F The thread is made of Nonsmooth
material.
Finish the thread path appropriately.
2)-A The thread path is not smooth.
Check and corrective measures
1-2) Thread tension (top or bottom)
is too high.
Cause (2)
Use a thin needle as much as possible. Use a KN needle (standard
needle).
(Example DB x 1 #11 - DB x 1KN #9)
Cause (1)
1-1) The needle is too thick.
To the next page
1. Puckering
Wrinkles developed around
stitches due to stitch
shrinkage or uneven material
feed.
Trouble
(2) Sewing performance
− 51 −
Lower cloth
Upper cloth
2-1) Feeding is inappropriate.
To the next page
Slippage
Cause (1)
1-5) Feeding is inappropriate.
From the previous page
2. Uneven material feed
The upper and lower cloths
are not evenly fed.
Trouble
Sharpen the top edges.
Replace the current feed dog with a new one having a smaller pitch.
Adjust the tilt so that the front end of the feed dog is higher than the rear
end.
Replace the current feed tooth with new one.
Reduce the feeding speed.
Use the cloth puller.
5)-B The tip of the feed dog is worn.
5)-C The pitch of the feed dog is too large.
5)-D The inclination of the feed dog is
inappropriate.
5)-E The parallel level of the feed dog is
inappropriate.
5)-F The feeding speed is too high.
5)-G Others
Set the feed dog with its front down.
Adjust the feed timing to the standard timing.
1)-D The tilt of the feed dog is not correct.
1)-E The feed timing is too late.
Use one with a smaller pitch.
Sharpen the top edges.
1)-B The top edges of the feed dog teeth are
worn.
1)-C The feed dog pitch is too large.
Lower the feed dog as long as sufficient feed power is ensured.
1)-A The feed dog is too high.
Use an aluminum bobbin (part No. B9117552A00)
Pull the material back by hand.
Lower the feed dog as sufficient feed power is maintained.
Check and corrective measures
5)-A Too high feed dog causes jumping at
high speeds.
Cause (2)
− 52 −
Bobbin
thread
Balloon
Needle thread
Cause (1)
To the next page
3-3) The stroke of the thread
take-up lever is too long.
3-2) The thread take-up spring is
inappropriately adjusted.
Increase the tension.
Readjust so that the spring does not touch the arm.
2)-B The tension is too low.
2)-C The spring comes in contact with the
machine srm.
Move the arm thread guide rightward to reduce the thread feeding with
the thread take-up lever.
Increase the stroke.
2)-A The stroke of the thread take-up spring
is too short.
Increase the 2nd thread tension.
Use a fluorocarbon resin presser foot or a nidax presser foot.
2)-C The presser is made from Nonsmooth
material.
3-1) The thread tension is too low.
Buff the sole.
2)-B The finish of the backside of the presser
is rough.
Reduce the feeding speed.
Minimize the pressure as long as material is properly fed.
Check and corrective measures
2)-A The pressure is too high.
Cause (2)
2-3) The feeding speed is too high.
2-2) Pressing is inappropriate.
From the previous page
2. “Balloon” stitches (loose
stitches and looping)
Thread knots are formed on
either side of material as a
random thread loop.
Trouble
− 53 −
Trouble
To the next page
3-7) The bobbin or bobbin case is
defective.
3-6) The thread path is defective.
3-5) The matters related to the
hook are inappropriate.
3-4) Knife thread guide position is
improper.
From the previous page
Cause (1)
7)-A The timing of feeding is inappropriate,
or the height of the feed dog is too low.
For cotton or spun thread, adjust the feed timing slightly later than the
standard timing, and adjust it slightly earlier than the standard for
synthetic thread. Increase the feed dog height (up to 1mm).
To prevent bobbin racing, use a bobbin with spring for prevention of
racing or put a thin cloth in the bobbin case.
Finish the thread path appropriately to correct threading.
5)-C The thread path has an obstacle.
6)-D The bobbin thread idles in the bobbin
case.
Finish the thread path appropriately.
5)-B The thread path has a flaw.
Replace the bobbin case.
Finish the thread path appropriately.
5)-A The thread path is not smooth.
6)-C The tension adjusting spring of the
bobbin case is defective.
Replace the hook.
4)-E The hook is defective. (thread catch)
The winding tension was too high or low.
Adjust the oil volume to the appropriate level.
4)-D Hook oil is insufficient.
6)-B Thread has not properly been wound
around the bobbin.
Increase the clearance to smooth the thread passing.
4)-C The clearance between the hook and
inner hook presser is too small.
Replace the bobbin or bobbin case.
Set the timing of the hook to the slightly early level for filament thread.
4)-B The timing of the hook is too late.
6)-A Inappropriate engagement between the
bobbin and bobbin case causes the
bobbin thread to be caught.
Set the timing of the hook to the standard or slightly late level for cotton
or spun thread.
Check and corrective measures
4)-A The timing of the hook is too early.
Cause (2)
− 54 −
Bobbin thread
Needle thread
4-2) The matters related to the
hook are inappropriate.
Replace the needle.
1)-C The needle tip is blunt.
Sharpen the blade top of the hook or replace the hook.
Correct the timing. (The proper timing depends on the type of material
and thread. In general, the timing should be set earlier for synthetic
thread or heavy-weight material, and it should be set later for
light-weight material.)
Properly adjust it with respect to the hook point. (In general, the needle
bar should be set higher for synthetic thread, and it should be set lower
for light-weight material.)
Minimize the clearance.
Wrap the thread around the needle.
2)-A The blade top of the hook is blunt or worn.
2)-B The timing of the hook is inappropriate.
2)-C The height of the needle bar is
inappropriate.
2)-D The clearance between the hook point
and needle is wrong.
2)-E The loop shape is unstable. (mesh type
materials)
Replace the needle.
Mount the needle appropriately. Replace the needle clamp screw.
Defective sewing is likely to occur when the needle recess portion faces
frontward.
1)-B The needle mounting direction is
inappropriate. The needle is not
mounted fully to the end.
1)-D The needle is too thin or thick for the
thread to be used.
Replace the needle.
1)-A The needle is bent.
Replace the needle. (It is advisable to use a ball-point needle for
synthetic thread.)
3-12) The needle is defective.
4-1) The needle is defective.
Change the needle or thread to be used.
3-11) The needle is too thin for the
thread to be used.
12)-A A burr exists on the tip of the needle.
Use a throat plate with a larger needle hole.
Adjust the timing of the thread tension disk floating with reference to 3.(11)-5).
Use a foot with a large thread relief on the backside.
8)-B The presser foot sole has little or no relief
(for thicker thread or larger stitch length).
9)-A The thread tension disk is floating.
Correct the height.
Check and corrective measures
8)-A The presser is floating.
Cause (2)
3-10) The needle hole of the throat
plate is too small.
3-9) The thread tension device is
defective.
To the next page
Skipped stitch
Cause (1)
3-8) Feeding is inappropriate.
From the previous page
4. Stitch skipping
The machine fails to form a
complete stitch.
Trouble
− 55 −
Thread
5-3) The thread take-up spring is
inappropriately adjusted.
5-2) The tension of the needle
thread is inappropriate.
5-1) The thread path (including the
throat plate and foot) is
defective.
To the next page
Material
Throat
Bobbin thread plate
Stitch
Thread breakage
Needle
Use one with a smaller needle hole.
7)-B The needle hole of the throat plate is
too large.
Check threading again and conduct correction if necessary.
1)-C The thread path has an obstacle.
Adjust the stroke of the thread take-up spring.
Adjust the tension of the thread take-up spring.
3)-B The tension of the thread take-up spring
is too high or too low.
Adjust the tension of the needle thread to eliminate random movement
of the thread between the 1st and 2nd thread tension portions.
3)-A The stroke of the thread take-up spring
is too long or too small.
2)-B The 1st thread tension is too low.
Adjust the tension of the needle thread to the appropriate level.
Finish the thread path appropriately.
1)-B The thread path has a flaw.
2)-A The tension of the needle thread is too
high or too low.
Finish the thread path appropriately.
1)-A The thread path is not smooth.
Replace the presser foot or presser bar.
Correct the presser foot height.
7)-A The presser is floating.
7)-D The parallel level of the presser is
inappropriate.
Reduce the tension of the thread take-up spring.
6)-B The tension of the thread take-up spring
is too high.
Use one with a smaller relief or with no relief.
Shorten the stroke of the thread take-up spring.
6)-A The stroke of the thread take-up spring
is too long.
4-6) The thread take-up spring is
inappropriately adjusted.
7)-C The thread relief on the back side of the
presser is too large.
Hasten the feed timing.
4-5) The feed timing is
inappropriate. (needle bent)
4-7) The material is
inappropriately stretched.
Reduce the speed.
Check and corrective measures
4-4) The speed is too high.
Cause (2)
Reduce the tension of the needle thread. Use silicon.
Cause (1)
4-3) The tension of the needle
thread is too high.
From the previous page
5. Needle thread breakage
The needle thread splits
finely or breaks during
sewing.
Trouble
− 56 −
Cause (1)
6-1) The needle has improperly
been attached.
5-5) The matters related to the
hook are inappropriate.
5-4) The needle is defective.
From the previous page
6. Thread breakage at back or
back-tuck sewing
Trouble
Replace the needle.
Use a ballpoint needle.
4)-E The needle is too thin or thick for the
thread to be used.
4)-F The needle tip is too sharp.
Long groove side
Indented side
Wrap thread around the needle.
About 10°
Attach the needle so that the long groove of the needle faces exactly to
the left or slightly toward the operator as illustrated.
Adjust the hook oil volume to the appropriate level.
5)-D Hook oil is insufficient.
1)-A The orientation of the needle is wrong.
Increase the clearance to smooth the thread passing.
5)-C The clearance between the hook and
inner hook presser is too small.
Sharpen the blade top of the hook or replace the needle.
Mount the needle appropriately. Defective sewing is likely to occur
when the needle recess portion faces frontward.
4)-D The needle mounting direction is
inappropriate.
5)-B The blade top of the hook is blunt or
worn.
Replace the needle.
4)-C The needle tip is blunt.
Smooth the thread path.
Replace the needle.
4)-B The needle has a flaw.
5)-A The thread path of the hook has a flaw.
Replace the needle.
Check and corrective measures
4)-A The needle is bent.
Cause (2)
− 57 −
Material
8-3) The speed is too high.
Use a shorter needle or a needle with longer shank (DA x 1)
2)-D The needle is too long.
Reduce the speed.
Use a thicker needle. For a KN needle (single needle), use a double
needle.
Replace the needle.
2)-C Needle is too thin.
2)-B The needle tip is blunt.
Replace the needle.
8-2) The needle is defective.
2)-A The needle is bent.
Reduce the tension of the needle thread.
Wrap the thread around the needle.
8-1) The tension of the needle
thread is too high.
To the next page
Staggering stitch
Staggering
Stitch
stitch
8. Staggering stitches
Some stitches stagger,
whereas they should be
aligned.
About 10°
Raise the needle bar.
Indented side
7-3) The needle bar is too low
Long groove side
Attach the needle so that the long groove of the needle faces exactly to
the left or slightly away from the operator as illustrated.
1)-A The orientation of the needle is wrong.
Accurately position it so that needle enters the center of the opening.
7-1) The needle has improperly
been installed.
7. Thread breakage at needle
entry or idle stitching.
Check and corrective measures
Cause (2)
7-2) The knife thread guide has
improperly been positioned.
Cause (1)
Trouble
− 58 −
Stitch
Fibers are broken
Material
Cause (1)
Replace the needle.
1)-C The needle tip is blunt.
Increase the feeding pitch as large as possible.
Lower the height of the presser tooth as low as possible.
3)-C The height of the presser tooth is too
high.
9-5) The feeding pitch is too small.
Reduce the pressure as low as possible.
3)-B The pressure is too high.
Keep the humidity at approx. 65% to prevent needle heat,
electrification, and friction.
Use a throat plate with a larger needle hole.
3)-A The needle hole of the throat plate is
too small.
Reduce the speed. (prevention of needle heat)
Use a ballpoint needle. (KN, S, J, B, U, Y, etc.)
Use a needle as thin as possible.
1)-B The needle is too thick.
1)-D The shape of the needle tip is
inappropriate. (different needle type)
Use silicon.
Try using B1418227T00 or B1418552A00.
1)-A The needle heat is too high.
6)-B The needle bar thread guide is
defective.
Correct threading.
Increase the pressure of the presser.
5)-C The pressure is too low.
6)-A Threading of the needle thread is
improper.
Replace the presser foot or presser bar.
5)-B The parallel level of the presser is
inappropriate.
Remove the play.
4)-C The feeder bar has a backlash in the
right-left direction.
Correct the presser foot height.
Mount the feed dog appropriately.
4)-B The feed dog is aslant mounted.
5)-A The presser is floating.
Replace the current feed dog with new one.
Check and corrective measures
4)-A The parallel level of the feed dog is
inappropriate.
Cause (2)
9-4) The room humidity is too low.
9-3) The material is excessively
tense.
9-2) The speed is too high.
9-1) The needle is defective.
8-6) Threading is inappropriate.
8-5) Pressing is inappropriate.
8-4) Feeding is inappropriate.
From the previous page
9. Material fiber breaks.
Material fibers are broken
by the needle during
sewing.
Trouble
− 59 −
Needle
thread
Bobbin
thread
10-5) The thread path is defective.
10-4) The thread take-up spring is
inappropriately adjusted.
10-3) The needle or bobbin thread
tension is too low.
10-2) The bobbin or bobbin case is
defective.
To the next page
Knot exposed on
the wrong side
Stitch
10-1) The matters related to the
hook are inappropriate.
10. Irregular stitch
Thread knots appear on
either side of material at
random.
Knot exposed
on the right
side
Cause (1)
Trouble
To prevent the bobbin from racing, use a bobbin with spring, or put a
thin cloth in the bobbin case.
2)-D The bobbin thread idles in the bobbin
case.
Finish the thread path appropriately.
Finish the thread path appropriately.
Finish the thread path appropriately to correct threading.
5)-B The thread path has a flaw.
5)-C The thread path has an obstacle.
Adjust the tension of the thread take-up spring.
4)-B The tension of the thread take-up spring
is too high or too low.
5)-A The thread path is not smooth.
Adjust the stroke of the thread take-up spring.
4)-A The stroke of the thread take-up spring
is too long or too short.
Increase the tension of the needle or bobbin thread.
Refer to “6. -(3). How to correct irregular stitches produced at high/low
speed”.
Replace the bobbin case.
2)-C The tension adjusting spring of the
bobbin case is defective.
2)-E The bobbin is inserted into the bobbin
case in the wrong direction.
Correct the bobbin thread winding tension or the position of the bobbin
winding tensioner.
2)-B Defective thread winding around the
bobbin winder causes the bobbin thread
to be caught.
Replace the bobbin or bobbin case.
Replace the hook or modify the thread path.
1)-B The hook is defective. (thread catch,
defective thread path, etc.)
2)-A The bobbin thread cannot be pulled out
smoothly due to poor fit between the
bobbin and bobbin case.
Adjust the oil volume to the appropriate level.
Check and corrective measures
1)-A Hook oil is too large or too small in
amount.
Cause (2)
− 60 −
The bobbin is scratched as
illustrated, and a burris left.
Scratch
Cause (1)
11-1) When a DAB-type hook
(11038650) is used, the
needle may come into contact
with the bobbin.
10-7) The stroke of the thread
take-up lever is too long.
10-6) The material is
inappropriately stretched.
From the previous page
11. The bobbin has a scratch.
Trouble
Use a presser with a smaller thread relief on the backside or without
thread relief.
Replace yhe presser foot or presser bar.
Replace the feed dog.
Adjust the clearance between the presser bar holder and lifting plate.
6)-B The thread relief on the back side of the
presser is too large.
6)-C The parallel level of the presser is
inappropriate.
6)-D The feed dog has poor parallelism.
6)-E The presser is floating.
Use the 11141355 (old DAC-type hook) which has needle guard effect
for a #11 needle.
When using a thicker needle, correct the needle guard.
Move the arm thread guide rightward to reduce the thread feeding with
the thread take-up lever.
Replace the current gauge with a new one having a smaller diameter
hole.
Check and corrective measures
6)-A The needle hole of the throat plate is
too large.
Cause (2)
6. BOBBIN CASE WITH AN IDLING PREVENTION SPRING
The DDL-8700-7 use bobbin cases with an idling prevention springs. Adjust the tension of the an idling
prevention spring as follows:
If the bobbin races
Increase the spring tension.
If loose stitches result
Decrease the spring tension.
(1) How to adjust the tension of the an idling prevention spring
1) Remove the spring as illustrated below, using an old sewing machine needle. (At this time, hold the
spring with your thumb to prevent it from jumping out.)
2) Adjust the spring pressure by changing the height of the arch of the spring.
3) Set ear ❶ first, and insert the sewing machine needle to push the central part of the spring, then set ear
❷. (Bobbin case spring : Part No. D1837-555-B0B)
1)
2)
3)
0.3 ± 0.2 mm
Ears
Change this height
(2) When using a bobbin case
When using a bobbin case with an idling prevention spring, be sure to orient the bobbin as shown below:
Rotation of bobbin
Rotation of bobbin
For a bobbin case with no anti-racing spring
(3) How to correct irregular stitches produced at high/low speed
If excessively tight stitches are
produced at low sewing speed:
Increase the bobbin thread tension and
the an idling prevention spring tension.
If loose stitches are produced
at low sewing speed:
Decrease the bobbin thread tension and
the an idling prevention spring tension.
(Caution) If the bobbin races or if irregular stitches are produced at high/low sewing speed,
it is advisable to use a bobbin case with an idling prevention spring.
− 61 −
7. BRIEFLY CHECKING THE ADJUSTMENT OF THE THREAD TRIMMER OF
DDL-8700-7 SERIES
Confirm checkpoints ❶ through ❻ following the procedure described below. It is basically required to
adjust the points properly.
Start
Turn ON the power to the sewing machine, and the
machine stops with the marker dot engraved on the
machine arm aligned with the marker dot (white) on the
pulley.
Turn OFF the power to the machine with the marker dot
aligned with the marker dot (white). Now, confirm
checkpoints ❶ through ❺.
Marker dot
White
Normal direction
of rotation
Cheakpoint ❶
Roller arm
Press the roller arm in
the direction of the
arrow to confirm that
the roller arm smoothly
projects and retracts.
Turn ON the thread
trimming solenoid
by hand and confirm
checkpoints ❷
through ❺.
Cheakpoint ❷
Roller arm
0.3 ± 0.2mm
− 62 −
Confirm that a clearance
of 0.3 ± 0.2 mm
(equivalent to
thickness of one or
two sheets of paper)
is provided.
Cheakpoint ❸
0.5 to 1 mm
Confirm that the
disk rises.
Cheakpoint ❹
Engraved marker line
Bobbin
presser
Confirrn that the picker
has reached the
engraved marker line.
Tum the pulley in the
reverse direction of
rotation until it stops.
Confirm that the marker
dot (red) engraved
on the machine arm is
aligned with the marker
dot (red) on the pulley.
This is the correct timing
Revese direction of the thread trimming
of rotation
cam.
Cheakpoint ❺
Marker dot
Red
Cheakpoint ❻
Check the backward travel amount of the moving knife.
It can be checked in the two different procedures. It is
recommended to take both procedures for more
accurate adjustments.
V-slit used for
adjusting the
position of the
moving knife
Home position
Confirmation (2)
Confirmation (1)
When the moving knife is
in the home position, the
V slit on the knife mounting
base is aligned with
the end of the moving
knife.
Moving knife
3 to 3.5 mm
Turn the pulley by hand
to make the moving knife
reach the backward travel
Center of
end. Now, confirrn that
needle
the top end of the moving
knife is spaced 3 to 3.5 mm
When the knife is in the
from the center of the needle.
backward travel end
− 63 −
MEMO
− 64 −
8. DRAWING OF THE TABLE
4 x ø3.4 on the bottom
surface, depth 20
(To be machined from
the bottom surfce)
2 x ø3.4 on the bottom surface, depth 20
ø18 through
hole
Drawer stopper installing
position (On the botton surface)
ø16 depth 30
2 - ø3.5 depth 4
ø35 through hole
2 - ø3.5 depth 4
2 - ø3.5 depth 10
ø13 through
hole
2-ø3.5 depth 10
JUKI logo type
2-ø3.4 on the bottom
surface, depth 10
(Drill a hole at the
time of set-up)
Y-Y
Rubber cushion installing
drawing for reference
C1.5 to C2.5 (For hinge side only)
Detail drawing of measure (2:1)
Type: Helvetica Reg Condensed
Condensed voided letters
Thickness 1.5
X–X
Rubber cushion installing
drawing for reference
Thickness 0.8
Thickness 0.5
Thickness 1.5
63 –−
–− 64
Part No. : 40095287
SC-920 + M92
CM001
This manual uses environment-friendly soyink.
ISO14001 : 2004
REG.NO.JSAE389
089
Juki Corporation operates an environmental management system to
promote and conduct the following as the company engages in the
research, development, design, sales, distribution,and maintenance
of industrial sewing machines, household sewing machines, industrial
robots, etc., and in the provision of sales and maintenance services
for data entry systems:
The development of products and engineering processes that are
safe to the environment
Green procurement and green purchasing
Energy conservation (reduction in carbon-dioxide emissions)
Resource saving (reduction of papers purchased, etc.)
Reduction and recycling of waste
Improvement of logistics efficiency (modal shift and improvement
of packaging, packing, etc.)
®
INDUSTRIAL SEWING MACHINE DIVISION
2-11-1, TSURUMAKI, TAMA-SHI,
TOKYO 206-8551, JAPAN
PHONE : (81)42-357-2371
FAX
: (81)42-357-2274
http://www.juki.com
Copyright © 2010 JUKI CORPORATION.
All rights reserved throughout the world.
Please do not hesitate to contact our distributors or agents in your area for further information when necessary.
* The description covered in this engineer's manual is subject to change for improvement of the
commodity without notice.
10 · 05 Printed in Japan (A)
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