JUKI MO-6800S Series Engineer's Manual
  1. Manuals
  2. Brands
  3. JUKI Manuals
  4. Sewing Machine
  5. MO-6800S Series
  6. Engineer's manual

JUKI MO-6800S Series Engineer's Manual

High-speed, overlock/safety stitch machine
Hide thumbs Also See for MO-6800S Series:
Table of Contents

Advertisement

Quick Links

High-speed, Overlock/Safety Stitch Machine
MO-6800S Series
ENGINEER'S MANUAL
40159525
No. E419-02

Advertisement

Table of Contents
loading
Need help?

Need help?

Do you have a question about the MO-6800S Series and is the answer not in the manual?

Questions and answers

Subscribe to Our Youtube Channel

Related Manuals for JUKI MO-6800S Series

Summary of Contents for JUKI MO-6800S Series

  • Page 1 High-speed, Overlock/Safety Stitch Machine MO-6800S Series ENGINEER’S MANUAL 40159525 No. E419-02...
  • Page 2 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 instruction in detail. And this manual describes “Standard Adjust- ment”, “Adjustment Procedures”, “Results of Improper Adjustment”, and other important information which are not covered in the Instruction Manual.
  • Page 3 TO ENSURE SAFE USE OF YOUR SEWING MACHINE Adjustment : It means replacement of parts, disassembly, and repair assembly. For the sewing machine, automatic machine and ancillary devices (hereinafter collectively referred to as "machine"), it is inevitable to conduct sewing work near moving parts of the machine. This means that there is always a possibility of unintentionally coming in contact with the moving parts.
  • Page 4 JUKI assumes no responsibility for damages or personal injury or death resulting from the use of the machine for any application other than the intended one.
  • Page 5 1. Be sure to use JUKI genuine table and table stand in order to prevent accident that can result in personal injury or death. If it is inevitable to use a table and table stand which are not JUKI genuine ones, select the table and table stand which are able to support the machine weight and reaction force during operation.
  • Page 6 7. If the machine cannot be normally operated after repair or adjustment, immediately stop operation and contact JUKI or the distributor in your area for repair in order to prevent accident that can result in per- sonal injury or death.
  • Page 7 5. Be sure to use JUKI genuine parts when replacing any of the machine parts. JUKI assumes no responsibility for any accident caused by any part other than JUKI genuine one. In addition, in the event you cannot replace parts within the specified range, immediately stop the re- placement work and ask JUKI or distributor in your area for replacement of the parts.
  • Page 8 Replacement of parts 1. In prevention of accident caused by unfamiliarity with the machine or electrical-shock accident, be sure to ask an electrical technician of your company or JUKI or distributor in your area for replacement of electrical components. 2. When it is necessary to open the control box containing electrical parts, be sure to turn the power off and wait for five minutes or more before opening the cover in order to prevent accident caused by un- familiarity with the machine or electrical-shock accident.
  • Page 9 2. In prevention of accident caused by unfamiliarity with the machine or electrical-shock accident, be sure to ask an electrical technician of your company or JUKI or distributor in your area for disassembly/as- sembly of electrical components. 3. When it is necessary to open the control box containing electrical parts, be sure to turn the power off and wait for five minutes or more before opening the cover in order to prevent accident caused by unfa- miliarity with the machine or electrical-shock accident.
  • Page 10 PRECAUTIONS TO BE TAKEN SO AS TO USE THE MO-6800S SERIES MORE SAFELY 1. So as to avoid electric shock hazards, do not open the cover of the electrical box of the motor or touch any part inside the electrical box with the power to the machine turned ON.
  • Page 11 CAUTION BEFORE OPERATION WARNING : To avoid malfunction and damage of the machine, confirm the following. • Read and understand well the content of this instruction book. • Know the functions of major parts and understand the notices. • Truely realize the meanings of all warning tags. •...

  • Page 12: Table Of Contents

    CONTENTS 1. Specifications ........1 (15) Adjusting the thread cam equipment (Applicable only to MO-6816S) ... 26 2. Names of major parts ......2 1) Adjusting the thread cam .......26 3. Model numbering system .....3 2) Adjusting the thread cam thread 4. Standard adjustment value ....4 guides A and B and the thread cam nail ............26 (1) Adjusting the needle height....

  • Page 13: Specifications

    By lever (with micro adjustment mechanism) ing method 16 Weight 27 kg 17 Lubrication Automatic lubrication type 18 Lubricating oil JUKI MACHINE OIL 18 (Equivalent to ISO VG 18) 19 Needle cooler Provided as standard Needle thread heat Provided as standard remover Micro presser lifting...

  • Page 14: Names Of Major Parts

    2. Names of major parts ❶ Presser foot lifting lever ❷ Presser foot (asm.) ❸ Thread stand ❹ Oil gauge ❺ Pulley ❻ Cloth plate cover ❸ ❶ ❺ ❹ ❷ ❻ – 2 –...

  • Page 15: Model Numbering System

    3. Model numbering system MO-6800S series model numbering system 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 M O 6 8 △ △ S ◇ □ △ △ ◇ ◇ ／ □ △ △ ◇ □ △ △ △ － □ □ △...

  • Page 16: Standard Adjustment Value

    4. Standard adjustment value (1) Adjusting the needle height WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment When the needle(s) is in the highest position, the needle height from the throat plate surface should be as shown below.
  • Page 17 Adjustment procedures Results of Improper adjustment 1. Take off the upper cover, loosen the clamping screw ❷ of needle Any other needle height than driving forked crank ❶ and move needle driving forked crank ❶ specified here will badly affect up or down to adjust the needle height.

  • Page 18: Adjusting The Lower Looper

    (3) Adjusting the lower looper WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment 1) Returning amount of the lower looper F : The distance between the blade point of the lower looper ❸ and the center of the needle ❹ should be as follows when the lower looper ❸...
  • Page 19 Adjustment procedures Results of Improper adjustment 1) Returning amount of the lower looper Excessive returning amount of Loosen clamping screw ❷ of lower looper support arm ❶ and ad- the lower looper tends to cause just lower looper ❸ to make adjustment of the returning amount. stitch skipping when filament thread is used.

  • Page 20: Positioning The Upper Looper Holder

    (4) Positioning the upper looper holder WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment H : The distance between the bottom surface A of the frame and the upper end of the upper looper holder pin ❷...
  • Page 21 Adjustment procedures Results of Improper adjustment 1. Loosen the clamping screw ❸ of the upper looper ball arm and Inaccurately positioned upper the clamping screw ❺ of the upper looper holder. looper holder will cause exces- 2. Adjust the clearance between the upper looper bracket ❹ and sive projecting amount of the the upper looper holder ❶...

  • Page 22: Positioning The Upper Looper

    (5) Positioning the upper looper WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment 1) The relationship between the needle and the upper looper E : The distance between the blade point of the upper looper ❸...
  • Page 23 Adjustment procedures Results of Improper adjustment 1) The relationship between the needle and the upper looper If dimension E is too small, an 1. Loosen the clamping screw ❷ at the top end of upper looper excessive clearance will be pro- bracket ❶...

  • Page 24: Adjusting The Double Chain Looper (Applicable Only To Mo-6816S)

    (6) Adjusting the double chain looper (Applicable only to MO-6816S) WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment 1) Returning amount of the double chain looper G : The distance between the blade point of the double chain looper ❸...
  • Page 25 Adjustment procedures Results of Improper adjustment 1) Returning amount of the double chain looper Excessive returning amount Loosen clamping screw ❷ of double chain lopper driving arm ❶ of the double chain looper will to make this adjustment. cause frequent stitch skipping when filament thread is used.

  • Page 26: Adjusting The Height And Clearance Of The Needle Guard

    (7) Adjusting the height and clearance of the needle guard WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment 1) For 1-needle or 2-needle overlock machine Make the needle guard ❸...
  • Page 27 Adjustment procedures Results of Improper adjustment 1) For 1-needle or 2-needle overlock machine Excessively close contact between the needle guard ❸ 1. Adjust needle guard ❸ with setscrew ❺ of the needle guard so and the needles ❷ will lead to that it lightly comes in contact with the needle ❷...

  • Page 28: Adjusting The Height Of The Feed Dog

    (8) Adjusting the height of the feed dog WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment ❷ ❺ ❻ ❹ ❷ ❺ ❶ ❻...
  • Page 29 Adjustment procedures Results of Improper adjustment 1. Turn the pulley to rise the feed dog to the highest point. If the feed dogs are too high, 2. Loosen the screw ❶ . and move the main feed dog ❷ up and the needles will be deflected down in order to keep the teeth side over the throat plate about and broken when sewing heavy-...

  • Page 30: Adjusting The Differential Feed Ratio

    (10) Adjusting the differential feed ratio WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment Differential feed ratio (Standard) Gathering 1 : 2, Stretching 1 : 0.7 / 60H ···...
  • Page 31 Adjustment procedures Results of Improper adjustment 1. Loosen differential feed adjusting nut ❷ . Move differential feed adjusting lever ❶ upward to perform stretching sewing, or down- ward to perform shirring. 2. When you want to move the lever ❶ only slightly, use differential feed minute-adjust screw ❸...

  • Page 32: Adjusting The Presser Foot

    (12) Adjusting the presser foot WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment 1) Adjusting the presser foot position Increase Decrease ❶ ❷ ❼...
  • Page 33 Adjustment procedures Results of Improper adjustment 1) Adjusting the presser foot position Uneven contact will result in bad 1. Loosen the presser adjusting screw ❶ and the setscrew ❼ of the straight material feed, weak feed presser foot. power, or puckering. 2.

  • Page 34: Positioning The Upper Knife Arm Shaft

    (13) Positioning the upper knife arm shaft WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment The upper knife shaft should be positioned 24 mm above the top surface of the throat plate when it is at its lowest position.
  • Page 35 Adjustment procedures Results of Improper adjustment 1. Remove the upper cover, loosen the clamping screw ❷ of the Improperly positioned upper upper knife driving arm ❶ , and turn the upper knife shaft ❸ to knife arm shaft will come in adjust the position from the top surface of the throat plate to 24 contact with the frame.

  • Page 36: Replacing The Upper And Lower Knives And Adjusting The Overedging Width

    (14) Replacing the upper and lower knives and adjusting the overedging width WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment 1) Replace the upper knife 2) Replace the lower knife 3) Adjusting the overedging width 4) Resharpening of the knife...
  • Page 37 Adjustment procedures Results of Improper adjustment The lower knife ❻ , if positioned 1) Replace the upper knife 1. Loosen the screw ❶ and move the lower knife holder ❷ to the too high, will catch materials or left. Then, tighten the screw ❶ a little. cause no contact of the press- 2.

  • Page 38: Adjusting The Thread Cam Equipment (Applicable Only To Mo-6816S)

    (15) Adjusting the thread cam equipment (Applicable only to MO-6816S) WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment 1) Adjusting the thread cam 2) Adjusting the thread cam thread guides A and B and the thread cam nail 3) Positioning the chain looper thread guide Level...
  • Page 39 Adjustment procedures Results of Improper adjustment 1) Adjusting the thread cam If the timing of the thread cam 1. Adjust the position of the thread cam ❽ by its setscrew ❶ with ❽ is too early, the needle  tip the needle  at their upper dead point so that the straight section will fail to enter a thread triangle, of the thread cam ❽...

  • Page 40: Adjusting The Looper Cover

    (16) Adjusting the looper cover WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment The looper cover ❷ should smoothly close without coming in contact with upper knife ❶ when slowly closing looper cover ❷...
  • Page 41 Adjustment procedures Results of Improper adjustment 1. Close looper cover ❷ , loosen setscrew ❸ , and move looper cover guide plate ❹ back and forth until the looper cover ❷ is brought to a position where the cover smoothly closes. 2.

  • Page 42: Adjusting The Needle Bar Lubricating Pin

    (18) Adjusting the needle bar lubricating pin WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment Thickness gauge ❶ ❸ ❹ [60H] ❷ ❺ 0.1 to 0.2 mm ❷...
  • Page 43 Adjustment procedures Results of Improper adjustment 1. Bring the needle bar ❹ to the lower dead point. If the clearance provided be- 2. Loosen the setscrew ❶ . tween the needle bar lubricating 3. Adjust a position of the needle bar lubricating pin ❷ so that a pin ❷...

  • Page 44: Positioning The Upper Looper Lubricating Pin

    (19) Positioning the upper looper lubricating pin WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment 1) Orientation of the lubricating pin Oil inlet A of upper looper lubricating pin ❶ should face upward. ❶...
  • Page 45 Adjustment procedures Results of Improper adjustment If the oil inlet A does not face 1) Orientation of the lubricating pin When upper looper lubricating pin ❶ is set with oil inlet A faced upward, oil will not be fed result- upward, lubricating hole B is in the lower section as observed ing in seizure.

  • Page 46: Positioning The Thread Take-Up Lever

    (20) Positioning the thread take-up lever WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment 1) Positioning the needle thread take-up lever and the needle thread guide MO-6804S MO-6814S** MO-6816S**...
  • Page 47 Adjustment procedures Results of Improper adjustment Perform the adjustment by the setscrews. Position of the needle thread guide ❶ and needle thread take-up lever ❷ is a very important decisive factor when making soft chains since the needle thread take-up amount is increased in this case. So, carefully position these parts.

  • Page 48: Lubrication And Drainage

    (21) Lubrication and drainage WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Standard adjustment 1) Lubrication oil ❶ ❹ ❸ ❷ 2) Drainage and refill the oil ❺...
  • Page 49 1. Remove the oil sight window ❶ from the oil inlet. Add lubricat- ing oil specifically made for machines which run at a super-high speed (JUKI MACHINE OIL #18) supplied with the unit or equiva- lent through the oil inlet. When the oil surface reaches the space between two marker lines on the oil gauge ❹...

  • Page 50: Additional Information And Precautions

    5. Additional information and precautions (1) Caution in assembly 1) Application of sealant * Used sealant : Three Bond 1212 (or equivalent) ① Bottom surface of upper looper guide support Apply a sealant to the bottom surface of the upper looper guide support ❶ , which contacts with the frame surface.
  • Page 51 ⑥ Portion of feed mechanism cover ❺ Apply a sealant to the mounting plane D of the feed mechanism cover ❺ . Apply a sealant along this plane. Apply a sealant evenly to the portion of feed bar presser E of the feed mechanism cover ❺ . Apply a sealant.

  • Page 52: Precautions To Be Taken With Respect To The Lubricating Components

    2) Precautions to be taken with respect to the lubricating components ① Feed bar components Be careful of the orientation of the oil shield rub- bers ❶ . Be careful of chamfered orientation. Operator's side ❶ (2) Motor pulley and belt ❶...

  • Page 53: Part Number Of Frame Support Plate Bolt

    (3) Part number of frame support plate bolt Part name Part number Qty Semi-sunken type Support plate bolt set (asm.) 70000265 Fully-sunken type Support plate bolt set (asm.) 70000884 (4) Inspection and replacement of the oil filter To extend the usage term, this machine has equipped an oil filter ❶...

  • Page 54: Maintenance

    6. Maintenance WARNING : 1. Turn off the power switch before carrying out cleaning. The machine may operate if the treadle is pressed incautiously, which could result in injury. 2. Be sure to wear protective goggles and gloves when handling the lubricating oil and grease so that they do not get into your eyes or onto your skin, otherwise inflammation can be resulted.

  • Page 55: Gauge Table

    (1) Gauge table AUXILIARY DIFFERENTIAL MODEL THROAT PLATE MAIN FEED DOG FEED DOG FEED DOG M O - 6 8 0 4 S - 0 E 4 - 3 0 H 4 0 1 - 5 9 8 2 7 4 0 1 - 5 9 8 2 0 7 0 0 - 0 0 7 8 2 4 0 1 - 5 9 8 3 6...

  • Page 56: Adjusting The Needle Height And Looper Timing

    7. Adjusting the needle height and looper timing (Unit : mm) Description Needle height Upper looper components Lower looper Double chain looper components components 1-needle 2-needle Safety stitch Height Projection Upper looper holder Returning Radius Returning Radius Classification 2-needle (left) (right) (left) amount...

  • Page 57: Troubles And Corrective Measures

    8. Troubles and corrective measures WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Trouble Cause (1) Cause (2) Checking order and adjusting procedure 1. Needle thread breakage 1-1) Threading 1-A)
  • Page 58 WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Trouble Cause (1) Cause (2) Checking order and adjusting procedure From the previous page 1-10) Deffective double 10-A) Refer to the clause referring to defective chain-off thread double chain-off thread.
  • Page 59 WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Trouble Cause (1) Cause (2) Checking order and adjusting procedure 3. Needle breakage 3-1) Needle entry 1-A) The needle entry has not been correct- Correct the needle entry.
  • Page 60 WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Trouble Cause (1) Cause (2) Checking order and adjusting procedure 5. Overlocking needle thread 5-1) Lower looper 1-A) The blade point has defective shape Replace the lower looper.
  • Page 61 WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Trouble Cause (1) Cause (2) Checking order and adjusting procedure 6. Lower looper stitches are 6-1) Threading 1-A) The thread has been entangled with a Refer to the threading diagram.
  • Page 62 WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Trouble Cause (1) Cause (2) Checking order and adjusting procedure From the previous page 7-5) Amount of thread 5-A) Excessive upper looper thread is fed, Slightly lower the looper thread take-up (left)
  • Page 63 WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Trouble Cause (1) Cause (2) Checking order and adjusting procedure 9. Triangle double chain looper 9-1) The needle point is 1-A) The needle point has been crushed and Refer to the clause relating to the needle point...
  • Page 64 WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Trouble Cause (1) Cause (2) Checking order and adjusting procedure 11. Overlocking chain-off thread is 11-1) Position of the throat 1-A) The throat plate has been improperly Correctly position the throat plate.
  • Page 65 WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Trouble Cause (1) Cause (2) Checking order and adjusting procedure From the previous page 12-4) Throat plate 4-A) A dent exists on the flat part between Repair or replace the throat plate, since such dent...
  • Page 66 WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Trouble Cause (1) Cause (2) Checking order and adjusting procedure 14. Double chainstitch needle 14-1) Thread tension 1-A) The looper thread tension is too high, Reduce the looper thread tension to a minimum,...
  • Page 67 WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Trouble Cause (1) Cause (2) Checking order and adjusting procedure 17. The looper thread bulges out 17-1) Knife width 1-A) The knife width is too small for the over- Use a knife having width suited to the overedging...
  • Page 68 WARNING : Turn OFF the power before starting the work so as to prevent accidents caused by abrupt start of the sewing machine. Trouble Cause (1) Cause (2) Checking order and adjusting procedure 21. Puckering (Mainly concerned 21-1) Needle 1-A) The needle is too thick.

  • Page 69: Drawing Of Table

    9. Drawing of table (1) Semi-sunken type Part No. : 40186299 – 57 –...

  • Page 70: Fully-Sunken Type

    (2) Fully-sunken type Part No. : 40186298 – 58 –...

  • Page 71: Auxiliary Table For Fully-Sunken Type

    (3) Auxiliary table for fully-sunken type Part No. : 40186300 – 59 –...
  • Page 72 Please do not hesitate to contact our distributors or agents in your area for further information when necessary. Copyright © 2015-2016 JUKI CORPORATION * The description covered in this engineer's manual is subject to change for improvement of the •...

This manual is also suitable for:

Mo-6804sMo-6814sMo-6816s

Table of Contents

Save PDF