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Saturday, March 14, 2015

Woven Fabric Defects with their Causes and Remedies

As in other industries, the goal of the textile industry is to manufacture defects-free products. However, defects do creep in at various stages of the processes of production, due to materials, machines or men.

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Fabric Defects with their Causes and Remedie

Faults of woven fabric with their causes and remedies

Warp way defects
Crack between stripes
A crack seen along the length of the fabric between the stripes woven with different weaves.
 
Causes
  • Differences in warp release due to uneven beam surface.
  • Differences in crimp relationship of ends grouped in separate dents in the reed and in weaves.
Remedies
  • Avoid uneven build of beam surface by proper system of denting at the sizing machine.
  • Ensure that denting at weaving is such that ends of the two weaves are not separated by a reed dent.
Double end
More than one end working in a heald eye without the adjacent end missing.
 
Causes
  • Sticky ends on weavers beam
  • Wrong drawing-in of ends through heald eyes.
Remedies
  • Take precautionary measures during sizing.
  • Bring the defect to the notice of the drawing-in operator.
  • Instruct weavers and supervisors to periodically check fabric to remove double ends.
Floats
Defect in a woven fabric where warp and weft threads do not interlace as desired.
 
Causes
  • Broken end getting entangled with the adjacent warp ends. The breaks between reed and healds are more prone to form floats, especially when the warp loses its elasticity due to over stretching or over-backing during sizing.
  • Knots with long tail ends leading to entanglement of ends.
  • Fluff with long tail ends leading to entanglement of ends.
  • Fluff or foreign matter trapped in the shed.
  • Broken heald unable to lift or lower the thread.
  • Lighter type of warp stop motion pins used on the loom.
Remedies
  • Attend to broken ends without delay on looms equipped with warp stop motion; ensure proper functioning of the same.
  • Avoid long tail ends in knots in weaving preparatory and weaving.
  • Ensure cleanliness of loom.
  • Take maximum possible care while blowing the looms.
  • Use screens to avoid fluff flying to adjacent looms.
  • Inspect the healds for wear before putting on a new beam.
  • Ensure proper selection of drop pins.
Misdraws
Incorrect positions of ends in the fabric causing considerable damage in fabrics with woven design or stripes.
 
Causes
  • Faulty drawing-in of beam.
  • Faulty drawing-in of broken ends by the weaver.
Remedies
  • Bring the defect to the notice of the drawing-in operator.
  • Ensure periodic inspection of the fabric on loom by the supervisory stuff.
Missing end
Void caused by a missing warp thread in the fabric.
 
Causes
  • Failure of weaver in attending to warp breaks immediately.
  • Warp stop motion not acting properly.
Remedies
  • Missing the incidence of lappers during sizing.
  • Use spare ends on loom as a substitute for the missing ends.
  • Instruct the weaver to attend to warp breaks immediately.
  • Discourage the weaver’s habit of waiting for the broken end on the beam to advance sufficiently for knotting.
  • Inspect the drop pins while putting on a new beam and weed out the defective ones.
  • Check the warp stop motion assembly.
Reedy fabric
Fine cracks appearing across the fabric between groups of warp ends, matching with the pattern of denting in the reed.
 
Causes
  • Excessive warp tension.
  • Late shed timing leading to lack of proper tension at beat-up.
  • Insufficient toughing of shade.
Remedies
  • Adjust the warp tension.
  • Resort to early shed timing.
  • Raise the back-rest 12-24 mm above the front-rest level.
Stitches
Individual warp thread floating over a group of weft threads. Defect is more prominent in synthetic blended warps due to static electricity generation and hairiness of these yarns.
 
Causes
  • Soft sized beam.
  • Inadequate amount of antistatic agent in the size recipe.
  • Improper tensioning of warp.
Remedies
  • Ensure proper sizing.
  • Ensure proper size recipe.
  • Prefer slightly higher tension on warp.
  • If necessary, introduce lease rods between the healds and the drop pins.
Thick end
A warp end having diameter larger than normal.
 
Causes
  • Excessive count variation.
  • Accidental mixed-up of counts in winding and warping.
  • Piecing up of broken end with a wrong thread during weaving.
Remedies
  • Avoid it.
  • Conduct frequent checks to avoid mix-up of counts.
  • Inspect the thrums provided on the loom.
Warp streaks
Stripes running in warp way direction characterized by apparent differences in shade from the adjoining portions, arising mainly as a result of variation in the amount of light transmitted and reflected from groups of threads.
 
Causes
  • Short, medium and long-term variations in warp and/or uneven spacing of dents in the reed. Coarser count and closer spacing of ends appear lighter while finer count and wider spacing appear darker in shade than the normal portion of the finished fabric.
  • Mix-up of yarns of different luster, count or blend proportion.
  • Faulty drawing-in ends, e.g. double ends, missing ends etc.
  • Variations in package and beam dyeing.
Remedies
  • Improve the quality of warp since normal control exercised on count variation proves inadequate to prevent streakiness.
  • Check the condition of reed.
  • Use all metal reeds which give better results compared to pitch-bound reeds.
  • Ensure early shed timing and lower warp tension to help lessen the prominence of streaks in the fabric.
  • Adopt good materials handling system with proper storage and identification of materials to avoid mix-up of yarns.
  • Bring the defect to the notice of operators.
  • Take care to match the shade when mixing a freshly dyed lot with the old stock, especially in the case of synthetic and blend materials.
Weft way defects
Broken pattern
Restricted to fabric woven with patterns on drop box looms. It occurs either when the sequence of weft colors to be put is disturbed or when the width of color band is affected.
 
Causes
  • Improper adjustment of pattern cards or lattices.
  • Weaver neglecting to adjust the pattern chain before restarting the loom after mending a break or a crack.
  • Inserting pick in a wrong shed after mending a weft break.
Remedies
  • Check and adjust the pattern cards or lattices at the start of beam.
  • Make the weaver’s quality conscious.
  • Resort to pick finding prior to restarting the loom.
Broken pick
Weft is inserted only for a portion of a pick.
 
Causes
  • Weft break or weft exhaustion on ordinary looms.
  • Weft break or improper size of bunch on auto-pirns.
  • Improper functioning of weft fork.
  • Weft change effected through weft fork mechanism on automatic looms.
Remedies
  • Check the shuttle for loose fitting of pirn or roughness of surfaces as these cause more weft breaks.
  • Check also the shuttle boxes for settings and surface condition to prevent cutting of weft.
  • Check the shuttle and shuttle boxes.
  • Ensure proper size of bunch on auto-pirns.
  • Maintain the weft-fork mechanism in good working condition.
  • Resort to pirn change by weft feeler mechanism.
  • Resort also to pick finding before restarting the loom.
Cut weft
A defect generally randomly distributed over the fabric, not clearly visible in the grey stage, but becomes pronounced in the finished fabric.
 
Causes
  • Improper condition or quality of emery roller covering.
  • Viscose yarn from old lot or of lower strength is used.
Remedies
  • Check the emery roller covering.
  • Ensure proper check on the quality of blended yarn.
Double pick
Two or more picks inserted in the same shed where only one is desired.
 
Causes
  • Failure of the weaver to find out the correct shed when restarting an ordinary loom.
  • Pirn change when affected by weft fork on automatic loom.
Remedies
  • Resort to pick finding while restarting.
  • Effect the pirn change with weft feeler mechanism.
Gout
Foreign matters like lint or waste or pieces of harness strapping and leather accessories woven into the fabric. 
 
Causes
  • Indiscriminate throwing of waste by weavers.
  • Foreign matter getting into the shed during weaving.
Remedies
  • Ensure cleanliness of machines and surroundings in the loom shed.
  • Keep frequent check on harness strappings and leather accessories for undue wear and replace them, if necessary.
Sloughing off
Thick bunches of yarn are woven into the fabric in the weft direction due to slipping off of coils of yarn from the pirn during weaving.
 
Causes
  • Improper package characteristics.
  • Softly wound pirns.
  • Harsh picking and/or poor shuttle checking.
  • Poor humidity conditions during the storage of pirns.
Remedies
  • Employ correct package characteristics in pirn winding.
  • Ensure proper yarn tension during pirn winding in the case of rewound weft and in spinning in the case of direct weft.
  • Check the picking and checking mechanisms.
  • Condition the weft before putting it on loom.
Slub
An abnormally thick place in the yarn finally appearing in the fabric.
 
Causes
  • Undrafted portion in the yarn.
Remedies
  • Minimize the incidence of slubs during spinning.
  • Clear the yarns effectively during winding.
Snarl
It is a short length of yarn, mostly weft, which has spontaneously doubled back on itself. The snarling tendency is latent in highly twisted yarns. In some fabrics, the snarls are found to be randomly spread over the width of the fabric, while in some other cases, they are restricted to a region at a fixed distance from one of the selvedges. 
 
Causes
  • Highly twisted weft.
  • Low weft tension.
  • Shuttle rebounding either due to harsh picking or poor checking.
  • Centre weft fork not set right.
Remedies
  • Condition the weft prior to weaving by steam conditioning, CMC conditioning or gumming.
  • Provide suitable drag in the shuttle.
  • Ensure smooth picking and adequate checking of shuttle in the boxes.
  • Check the setting of centre weft fork.
Starting marks
A thick or thin place is produced in the fabric due to variation in pick density while starting the loom.
 
Causes
  • Weaver letting back the fell of the fabric too close to the reed by faulty adjustment of take-up motion.
  • Faulty functioning of anti-crack motion.
Remedies
  • Instruct the weavers about the correct procedure.
  • Ensure correct functioning of the motion.
Cracks
A higher pick density than the normal is referred to as starting mark while a lower pick density is referred to as crack.
 
Causes
  • Improper letting back of the fell of the fabric.
  • Improper lifting of the dead weights on let-off motion while adjusting the warp tension.
  • Faulty functioning of anti-crack and weft fork mechanisms.
  • Snagging of warp due to the shed being kept open for exceptionally long periods.
Remedies
  • Undrafted portion in the yarn.
  • Guide the weavers about the right adjustment.
  • Set the mechanisms properly.
  • Stop the looms at healds leveled position so as to ensure minimum of warp tension during the stoppages.
Thick and thin places
Weft bars differing in appearance and repeating several times along the fabric.
 
Causes
  • Irregular let-off.
  • Faulty take-up.
Remedies
  • Set the let-off and/or take-up motion properly.
Weft bars
Weft way bands which are clearly distinguished from the rest of the portion of the fabric. The bars may be restricted for a particular length of fabric or may repeat at fixed intervals.
 
Causes
  • Periodic count variation in the weft yarn arising out of roller eccentricity or mechanical defects in the spinning preparatory processes.
  • Mixing of weft of – different counts, different twist levels, different directions of doubling twist and different brightness levels especially in filaments.
  • Mixing of spun blended yarns produced from synthetic fibres of different merge numbers.
  • Manufacturing defect in filaments like variation in denier.
Remedies
  • Ascertain and rectify the source of periodic count variation.
  • Take due care to avoid mix-up of weft during pirn winding and/or weaving.
  • Resort to segregation of packages in weft preparation.
  • Conduct a dyeing trial on a few pieces before taking up bulk dyeing.
Weft floating on one side
Causes
  • Shedding either uneven or tilted on one side when connecting band is broken.
  • Too weak a picking force from one end leading to passage of shuttle after the shed is crossed.
Remedies
  • Correct the shedding.
  • Correct the picking force.
Wrong pick density
Causes
  • Wrong pick wheel fixed in the take-up mechanism due to carelessness of line jobber.
  • Coarser of finer weft used by mistake.
Remedies
  • Ensure strict supervision on pick density at the start of a beam.
  • Take precautionary measures.
Other fabric defects
Hole or tear in fabric
A defective portion in the fabric marked by distortion or cutting of warp and weft.
 
Causes
  • Mechanical faults in loom.
  • Weavers tapping the fabric with the shuttle tip or pirn on the front rest when inserting a new pirn.
  • Carelessness of the weaver in removing gout.
  • Holes form during the finishing processes due to the presence of foreign matter.
Remedies
  • Rectify the mechanical faults.
  • Make the weaver quality conscious.
  • Take precautions in weaving to avoid incidence of woven foreign matter.
Smash
A damaged spot in the fabric with many broken ends and floating picks due to shuttle being trapped in the shed.
 
Causes
  • Incorrect timing of shedding and picking.
  • Improper starting of loom.
  • Too weak or too harsh checking of shuttle.
  • Improper working of loose reed and knock-off mechanisms.
Remedies
  • Tune the loom properly.
  • Tune the checking mechanism.
  • Tune the mechanisms properly.
Temple marks
Small pin holes appearing near the selvedge zones and being more prominent in fine and superfine varieties.
 
Causes
  • Incorrect selection of temples.
  • Improper setting of temple cap.
  • Temple rings not moving freely.
Remedies
  • Select the temples to suit the quality of fabric.
  • Ensure that the cap is not set too close to the temples and that there is sufficient gap for smooth passage of fabric over the temples.
  • Ensure cleanliness of temple assembly.

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About the Author :

He is Md. Abu Sayed from Naogaon, Bangladesh. He is a Textile Engineer and working as a Testing Engineer at Bureau Veritas CPS (BD) Ltd. He also Likes article writing on Textile and Clothing Technology.

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4 comments:

  1. Good article and very useful information. Thanks for this post.

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