Juki DDL-8700-7: This industrial-grade sewing machine is designed for high-speed, heavy-duty applications. Its advanced features and reliable performance make it an excellent choice for garment construction, upholstery, and other demanding sewing tasks. With its automatic thread trimmer, the Juki DDL-8700-7 simplifies the sewing process and enhances productivity.
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® 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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1-Needle, Lockstitch Machine
Automatic Thread Trimmer
High-speed operation
Heavy-duty construction
Adjustable stitch length and width
Easy-to-use controls
Durable and reliable
Refer to the 'Adjustment of the needle stop position' section of the manual for detailed instructions.
Follow the steps outlined in the 'Replacing the moving knife' section of the manual.
Refer to the 'Adjustment of the timing of the thread trimmer cam' section of the manual for specific instructions.
Adjust the tension using the tension disc located on the top of the machine.
Refer to the troubleshooting section of the manual for common issues and solutions.
How does the thread trimming mechanism work?
The thread trimming mechanism involves several steps, including the release of thread tension. When the machine is set to "ON," the needle goes up, and then the thread tension is released as part of the process.
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