Unicorn LS2-H520 Operation Manual Download Page 32

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TROUBLESHOOTING GUIDE

Pro blem

Cau se

Check

Solution

Page

Needle thread

slack.

Insufficient needle
thread tension

―

Increase needle
thread tension.

Excessive needle

thread tension

―

Decrease bobbin

thread tension.

Bobbin thr ead

slack.

Excessive needle

thread tension

―

Decrease needle

thread tension.

Insufficient needle

thread tension

―

Increase bobbin

thread tension.

Improper loopin g

stit ch tighten in g

Rough thread path

Thread path

Polish with fine

sandpaper.

Poor bobbin rotation

Tension of bobbin

thread leader

Replace bobbin,

rotary hook.

Rotary hook to rotary
hook stop gap

too small

Gap

Adjust needle to

rotary hook timing.

Improper th read

cutt in g

a. Needle,

bo bbin

thre ads not

cut

b. Nee dle

thre ad

not cut

c. Bo bbin

thre ad

not cut

Movable knife, fixed

knife do not overlap.

―

Adjust knives

Movable, fixed knife

edges worn or rough.

Knives

Replace knives.

Movable knife does

not move

Thread cutter
signal

transmission

  Check  electrical
  circuits;  replace
  thread  cutter
  solenoid.

Improper needle

installation

Needle facing

Reinstall needle.

  Last  stitch  skipped,
  needle  thread  not
  caught  by  thread
  cutter.

Thread take-up
spring stroke

Adjust thread
take-up spring.

Movable knife, fixed

knife do not overlap

―

Adjust knives.

Movable, fixed knives

dull.

Knives

Replace knifes.

Movable knife, fixed

knife do not overlap

―

Adjust knives.

Summary of Contents for LS2-H520

Page 1: ...LS2 H520 LS2 H5200 SINGLE NEEDLE NEEDLE FEED LOCK STITCH SEWING MACHINE WITH THREAD TRIMMER 1 OPERATION MANUAL PART BOOK...

Page 2: ......

Page 3: ...symbol at left means beware of injury This symbol indicates something that you must not do This symbol indicates something that you must do The picture inside the circle indicates the nature of the t...

Page 4: ...5 off A S 33 2 40 25 OFF A S A S...

Page 5: ...belt covers to the machine head and motor 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...

Page 6: ...placing the bobbin and needle when not using the machine and when leaving the machine unattended For machines with automatic presser lifter do not touch the solenoid section because if becomes hot dur...

Page 7: ...rician to carry out any maintenance and inspection of the electrical system Turn off the power switch and disconnect the power cord from the wall outlet at the following times otherwise the machine ma...

Page 8: ...act your nearest UNICORN dealer The positions of the labels may vary slightly depending on the model of sewing machine or motor 1 2 Be sure to connect the ground If the ground connection is not secure...

Page 9: ...ing machine is first turned on verify the rotational direction of the pulley with the power on The pulley should rotate counterclockwise when viewed from the pulley Power must be turned off when the m...

Page 10: ...L DESCRIPTION 7 1 Upper shaft and needle bar mechanism 7 2 Thread wiper 7 ADJUSTMENT 8 16 1 Adjusting the needle bar height 8 2 Adjusting the rotary hook position 8 3 Adjusting the rotary hook holder...

Page 11: ...1 How to install the belt V V 13mm 16mm Tilt back the machine head and place the belt onto the motor pulley and machine pulley Press belt with a finger force of 5 N and adjust the nut so that there is...

Page 12: ...he oil cover Screw Wipe off any contamination from the magnet and the oil pan Use the oil specified by Spindle15 2 Adjusting lubrication for upper shaft and rotary hook 1 1 Upper shaft lubrication Rem...

Page 13: ...he machine with the needle tip below the needle plate when the needle position switch is set to the needle down position Back treadle the pedal to position and release it to neutral to trim the thread...

Page 14: ...4 OPERATION 3 Threading the needle...

Page 15: ...bin case tension spring 3 Pull the thread from the bobbin case tension spring 5 Winding the bobbin thread 1 2 3 4 1 Fit the bobbin in the bobbin winder shaft 2 Depress the joint as far as it will go 3...

Page 16: ...tension at this time is 25 30g To adjust the operation range of the thread take up spring loosen the set screw and turn the thread tension bracket assembly To adjust the tension of the thread take up...

Page 17: ...turned on the thread trimming solenoid activates pressing the thread trimming cam lever stud The roller shaft of the thread trimming cam lever assembly secured by the thread trimming cam lever stud i...

Page 18: ...rejector needle bar bush Then firmly tighten the screw A 0 0 5mm 0 0 05mm Align the bottom reference line of the needle bar with surface A of the needle bar oil rejector needle bar bush by turning the...

Page 19: ...heck that the needle tip is as indicated below For thin materials The needle tip is aligned with tips of the feed dog and the upper surface of the needle plate For thick materials There is a 5mm gap b...

Page 20: ...parallel loosen the screw of the needle feed arm then move the needle bar bracket forward or backward 2 Feed dog position Set the feed regulating dial to maximum and turn the machine pulley Check that...

Page 21: ...m 3 0 6 0 8mm 4 0 5mm 40Kg 1 Loosen the screw and turn the machine pulley until the needle bar is raised 5 mm above its lowest position then depress the thread trimming solenoid 2 With the thread trim...

Page 22: ...the indentation of the thread trimming clutch 3 With the thread trimming solenoid depressed turn the machine pulley Adjust the movable knife and the fixed knife so that they overlap when the rotation...

Page 23: ...ve the feed bracket up or down 1 2 2 90 1 When the feed dog is fully raised its angle is properly adjusted if the circle on the feed bracket shaft aligns with the index on the feed rock shaft arm 2 To...

Page 24: ...ard and backward at the inching speed 215 spm 3 Adjust as follows when the forward and backward stitch lengths are different 1 Remove the rear plate 2 Loosen the screw 3 When the forward stitch length...

Page 25: ...osition there should be a 9 5 11 5 mm gap between the upper surface of the needle plate and the needle tip with thin or medium materials or a 10 12 mm gap with thick materials If adjustment of needle...

Page 26: ...Raise the presser foot using the presser bar lifter 2 Remove the screw and the needle plate 3 Remove the screws and the feed dog 4 Remove the screws and the auxiliary needle plate 5 Turn the machine p...

Page 27: ...17 4 4 16 15 15 15 4 4 4 6 6 6 2...

Page 28: ...y hook timing 15 Thread wiper too high Thread wiper position Adjust thread wiper position with screw Thread breakage Improper threading Threading Rethread 4 Bent needle Blunt needle tip jammed eye Nee...

Page 29: ...19 4 4 1 4 4 15 15 15 6 6...

Page 30: ...esser foot contact Presser bar pressure Tighten presser foot adjustment screw Presser bar height Adjust presser bar height Improper needle to rotary hook timing Needle bar rise Adjust needle to rotary...

Page 31: ...21 6 6 6 6 puff 15 19 23 4 22 19 23 19...

Page 32: ...ok stop gap too small Gap Adjust needle to rotary hook timing 15 Improper thread cutting a Needle bobbin threads not cut b Needle thread not cut c Bobbin thread not cut Movable knife fixed knife do no...

Page 33: ...23 6 1 22 6 24 24 24 24...

Page 34: ...ead cutter signal not transmitted Check circuits refer to motor adjustment manual Thread wiper does not function Needle thread remainder too long Adjust pretension 6 Timing too early wipes thread befo...

Page 35: ...25...

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Unicorn LS2-H520, Operation Manual

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