Knitted fabric faults and their remedies


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Knitted fabric faults and their remedies

  1. 1. Total Textile Process at a Glance
  2. 2. PROJECT ON Root Causes Analysis of knitted Fabric Faults & Their Remedies 33
  3. 3. Content  Introduction  Causes of Fabric faults due to yarn  Causes of Fabric faults due to knitting  Causes of Fabric faults due to Dyeing & Finishing  Conclusion 44
  4. 4. Introduction Due to increasing the demand for quality knitted fabrics, high quality requirements are today greater since customer has become more aware of “Non-quality" problems, in order to avoid fabric rejection, knitting mills have to produce fabrics of high quality, constantly. Detection of faults during production of knitted fabric with circular knitting machine is crucial for improved quality and productivity. Any variation to the knitting process need to be investigated and corrected. The high quality standard can be guaran-teed incorporating appropriate quality assurance. Industrial analysis indicate that quality can be improved, and defect cost minimized, by monitoring of the circular knitting process. 55
  5. 5. Our aim of this project is to study on root causes analysis of knitted fabric faults. To do so we have collected various type of faults from many industries and classify them in a systematic manner 66
  6. 6. Causes of Fabric faults due to Yarn Almost all the defects appearing in the horizontal direction, in the knitted fabric are, yarn related.  These defects are mainly: I) Barriness II) Spirality III) Shrinkage IV) Thick & thin place 77
  7. 7. I). BARRINESS Definition: Barriness defect appears in the Knitted fabric, in the form of horizontal stripes of uniform or variable width. 88 Fig: Barriness
  8. 8. Causes Of Barriness: factors which may cause or contribute to barre are listed as follows:  Raw material/fiber  Yarn formation /supply  Knitting machine 9
  9. 9. Raw Material/Fiber: Failure to control fiber diameter (micronaire or denier) from lay down to lay down. Too high a C.V. of micronaire in the lay down for a given mill's opening line blending efficiency. Failure to control the fiber color in the mix (grayness Rd, yellowness +b). 10
  10. 10. Yarn Formation/Supply:  Poor blending of fiber in opening through finisher drawing.  Mixing yarns of different counts.  Mixing yarns from different spinning systems.  Mixing yarns with different twist level/twist direction.  Mixing yarns with different degrees of hairiness.  Mixing yarns with different amounts of wax.  Excessive back winding or abrasion during this process. 11
  11. 11. Knitting Machine:  Improper stitch length at a feed.  Improper tension at a feed.  Variation in fabric take-up from loose to tight.  Excessive lint build-up.  Variation in oil content.  Worn needles, which generally produce length direction streaks.  Uneven cylinder height needles (wavy barre).  Double feed end. 12
  12. 12. Remedies:  Ensure uniform Yarn Tension on all the feeders.  The average Count variation in the lot, should not be more than + 0.3  Ensure that the yarn being used for Knitting is of the same Lot / Merge no.  Ensure that the hardness of, all the yarn packages, is uniform, using a hardness tester. 13
  13. 13. II).SPIRALITY Definition: Spirality appears in the form of a twisted garment, after washing. The seams on both the sides of the garment displace, from their position & appear on the front & back of the garment. 14 Fig: Spiraility
  14. 14. Influencing Factors: A) Influence of yarn properties  Count  Twist  Blend B) Influence of fabric properties:  Fabric Stitch length:  Fabric Structure  Fabric Tightness 15
  15. 15. (III). SHRINKAGE  A dimensional change resulting in a decrease in the length or width of a specimen subjected to specified conditions is known shrinkage. Shrinkage is mainly due to yarn swelling and the resulting crimp increase during washing in case of cotton fabrics 16
  16. 16. Causes of Shrinkage:  Twist factor: twist factor increases so that shrinkage will be increases,  Stitch length: stitch length increases so that shrinkage will be increases,  GSM: GSM increases so that shrinkage will be increases 17
  17. 17. Remedies of Shrinkage  Keep the Grey Fabric in loose plated form, immediately after the roll is cut.  Store the finished fabric also in the plated form & not in the roll form.  Allow the fabric to relax properly, before it is cut.  Give maximum overfeed to the fabric, during the processing, on the Stenter, Compactor & the Calendaring machines. 18
  18. 18. (IV) Thick & Thin Places It causes due to yarn problem. If thick & thin places remain in yam & fabric is knitted with that yarn, then, this problem found in fabric. Fig: Thick Thin Place 19
  19. 19. Causes of Fabric faults due to Knitting  Almost all the defects appearing in the vertical direction, in the knitted fabrics, are as a cause of bad Knitting Elements. And some defects appear randomly in the knitted fabrics, due to the wrong knitting machine settings & that of the machine parts  About Different type of faults are discuses bellow 21
  20. 20. Cracks Or Holes Local holes obtained when yarn breaks during loop formation. Causes  Presence of knot in yarn.  Weak places in yarn.  Yarn tension too high.  Yarn too dry.  Yarn - guide not properly set,  Poorly lubricated yarn. Fig: Hole 22
  21. 21. Remedies:  Use of flat knots.  Yarn regularity control.  Yarn consumption & coulier re-adjustment.  Precise yarn - guide resetting.  Air humidification.  guide blowing.  Use of protective filter creel. 23
  22. 22. Pin Hole Causes:  Improper tension.  Same drive for both knit & tuck stitch.  Curved needle latch. Remedies:  Different drive have to maintained Needle has to change.  Needle has no change. Fig: Pin Hole 24
  23. 23. Fly Contaminations Causes:  Presence of dead fibers & other foreign materials, such as; dyed fibers, husk & synthetic fibers etc.  Dead fibers do not pick up color during Dyeing. 25 Fig: Fly contamination
  24. 24. Remedies  Use rich fiber mixing for the yarns, to be used for Knitting, in order to have less dead fibers, appearing in the fabric.  Rigid control measures in the Blow Room, to prevent the mixing of foreign matters in the Cotton mixing 26
  25. 25. Needle Broken Causes:  High Yarn Tension  Bad Setting of the Yarn Feeders  Old & Worn out Needle set Remedies:  Ensure uniform & the right Yarn tension on all the feeders.  Keep the recommended gap, between the Yarn Feeders & the Needles.  Periodically change the complete set of needles. Fig: Needle Broken 27
  26. 26. Sinker Mark Causes:  Sinker not cleans.  Defected /broken sinker.  When darts deposited in sinker, it is raised & causes this fault. Remedies:  Sinker has to be clean.  It should be checked that the sinker having correct thickness and depth.  Replacement of defected sinkers. 28 Fig: sinker mark
  27. 27. Stains or Oil Lines Causes:  Grease & Oil stains from the unguarded moving machine parts  Fabric touching the floors & other soiled places, during transportation, in the trolleys. 29 Stains appear as spots or patches of grease, oil or dyes of different color, in a neat & clean finished fabric surface Fig: Stain or oil line
  28. 28. Remedies:  Wash & clean the dyeing machine thoroughly, after dyeing every dye lot.  Follow the dyeing cycle of Light- Medium- Dark shades & then the reverse the cycle, while dyeing the fabric.  All the lubricated moving machine parts, should be protected, with safety guards 30
  29. 29. Fabric Press Off  Fabric press off appears, as a big or small hole in the fabric, caused due to the interruption of the, loop forming process, as a result of the yarn breakage, or closed needle hooks. 31 Causes:  End breakage on feeders, with all needles knitting.  Yarn feeder remaining in lifted up position, due to which, the yarn doesn’t get fed in the hooks of the needles. Fig: Press off
  30. 30. Remedies:  Needle detectors, should be set precisely, to detect the closed needles & prevent the fabric tube from completely pressing off.  Proper yarn tension should be maintained, on all the feeders. 32
  31. 31. Lycra out Causes:  Fail to catch the Lycra yarn by needle.  Low tension of Lycra yarn.  Lycra yarn breakage.  Faulty auto stop motion Remedies:  Ensure the feed of lycra yarn to every needle.  The tension of lycra yarn should be uniform.  Auto stop motion should work properly 33 Fig: Lycra out
  32. 32. Lycra Drop Causes:  Low tension of Lycra yarn  Fail to catch the Lycra yarn by needle Remedies:  Ensure the feed of lycra yarn to every needle.  The tension of lycra yarn should be uniform. 34
  33. 33. Slub Causes:  Usually caused by a thick or heavy place in yarn or by ling getting onto yarn feeds. Remedy:  By using Good quality yarn Fig: Slub 35
  34. 34. Causes of Fabric faults Due To Dyeing & Finishing 37
  35. 35. The Dyeing and finishing related defects are, as follows Shade variation/Uneven shade Pin-hole damage Crease mark Dye spots Dead cotton on dyed cotton 38 Wrong slitting Lycra burn Band line Dust
  36. 36. Shade Variation/Uneven Shade  Sometimes, there appears to be a difference in the depth of shade between the roll to roll & from place to place, in the same roll. The defect will show up clearly in the garments manufactured from such fabric. Causes:  Shade variation can be as a result of mixing of the fabrics of two different lots.  Shade variation is also caused by the variation in the process parameters i.e. Time, Temperature & Speed etc. from one fabric roll, to the other. 39 Fig: Shade Variation/Uneven Shade
  37. 37. Shade variation can appear to be in fabrics with GSM variation, caused due to the uneven stretching, unequal fabric overfeed % etc. Remedies:  Ensure that the grey fabric used for one shade is knitted from the same lot of the yarn.  Ensure that the same process parameters (Width, Overfeed, Temperature & Machine Speed etc.) are used, for each roll of a dye lot. 40
  38. 38. Pin Hole Damage: Causes: Oxidation of the knitting oil/lubricant on the fabric stored for a long duration. Presence of sharp metallic part in some parts of machine Presence of heavy metal ions in peroxide bath. Remedies: Check presence of any sharp object in machine Provide magnetic filters in water/ steam line 41 Fig: Pin Hole Damage
  39. 39. Crease Mark:  In knit dyeing crease mark is a common dyeing fault. Causes:  More cycle time.  Faulty plaiting device.  Slack on tight selvedge causes creases at an angle to each selvedge.  Incorrectly set bowed-expander.  Variation of heating and cooling rate.  Improper fabric movement. Remedy:  Anti- creasing agents are used to avoid crease mark problem. 42 Fig: Crease Mark
  40. 40. Dye Spots Causes: These are most often caused by operators not correctly mixing and thoroughly dissolving the dyestuff, in the right amount of water. Dye bath hardness. Not agitation of dyestuff. Remedies:  Use adequate amount sequestrate to lower bath hardness.  Proper agitation. 43 Fig: Dye Spots
  41. 41. Dead Cotton On Dyed Cotton: Causes: Poor quality cotton More abrasion during process Remedies: Try to minimize the abrasion during process Use acid Cellulosic softener 44 Fig: Dead Cotton On Dyed Cotton
  42. 42. Wrong Slitting: Causes: It causes due to operator carelessness. Sometimes workers do not slit fabric through slitting mark. Remedies:  Operators have to slit fabric through slitting mark or fed fabric in slitting m/c in proper way so that m/c can slit fabric through slitting mark 45 Fig: Wrong Slitting
  43. 43. Lycra Burn: Cause: Overflow heat on the fabric during heat setting. Incorrect speed of stenter m/c during heat setting. Remedies:  Provide correct temperature in stenter m/c.  To keep correct speed of stenter m/c. 46 Fig: Lycra Burn
  44. 44. Band Line: Causes: If the fabric is wet condition in long time. During drying the fabric if any part of the fabric is wet then it can occur. Un proper fixing during dyeing Remedies:  To use short time for wet conditioning of the fabric.  Equal drying of the fabric.  Proper fixing during dyeing. 47
  45. 45. Dust: Causes: Due to dirty finishing floor. Unclean the trolley of finishing floor. Due to unclean the m/c surface. Unclean the compactor m/c after using the varies color of fabrics. Drop the footstep in white fabric. Remedies:  To keep clean the finishing floor.  Clean the trolley of finishing floor.  To clean the m/c surface.  Clean the compactor m/c after using varies color of fabrics. 48 Fig: Dust
  46. 46. CONCLUSION: Detection of faults during production of knitted fabric is crucial for improved quality and productivity. This presentation will present and discuss the detection of faults and malfunctions during the production remedies of knitted fabric. We believe that our work will help the knitters to identify the source of de-tected faults & proposes specific solutions for theses faults causes. So Knitters can take necessary remedial steps to overcome the faults. 49
  47. 47. 1. Yarn Manufacturing Technology Link : Technology/485014954866808 2. Fabric Manufacturing Technology Link : Technology/459520217425605 3. Garments Manufacturing Technology Link : Technology/472364799463126 3. Wet processing Technology Link : /468645219825404 4. Fashion-Design-and-Technology Link : Technology/587655294583875?ref=ts&fref=ts My Facebook Textile related Pages (Visit My Blog for more Info )