Fabric defects in woven and knitted fabric - hitesh choudhary

FABRIC DEFECTS

Hitesh Choudharywww.facebook.com/hitesh.choudhary1

Introduction

Defination of defect : i. An imperfection that impairs worth or utility.ii. Want or absence of something necessary for

completeness or perfection.iii. A fault that spoils the material.

Fabric defect : A Fabric Defect is any abnormality in the Fabric that hinders its acceptability by the consumer.

Importance of fabric defect

• Due to the increasing demand for quality fabrics, high quality requirements are today greater since customer has become more aware of poor quality problems.

• To avoid Rejection of fabric, It is necessary to avoid defects.

• Price of fabric is reduced by 45%-65% due to the presence of defects.

• Company image will go down.

List of fabric defects in woven fabrics

• Coloured flecks• Knots• Slub• Broken ends woven in a bunch• Broken pattern• Double end• Float• Gout• Hole, cut, or tear• Lashing-In• Local distortion

• Missing ends• Missing Pick• Oil and other stain• Oily ends• Oily picks• Reed mark• Slough off• Shuttle smash• Snarls• Stitches• Untrimmed loose threads• Weft bar

Coloured Flecks

COLOURED FLECKS : Presence of coloured foreign matter in the yarn.

CAUSES : Cotton fibres getting contaminated during the ginning stage with leaves, immature fibre, yellow fibre, etc.

MENDING: Coloured portion is removed from the yarn with a plucker. The resultant bare patch can be corrected by combing with metallic comb.

KNOTS

Knots : Knot is a fastening made by tying together the ends of yarn.

CAUSES : Thread breaks during process of winding, warping, sizing or weaving.

MENDING: Non Mendable.

SLUB

Slub : Slub is a bunch of yarn having less twist or no twist and has a wider diameter compared to normal spun yarn.

CAUSES : Improper carding/combing. Broken tooth in the chain of gear system.

MENDING: The slub should be cut with the clipper from both the ends. The resultant bare patch can be corrected by combing with a metallic comb or by insertion of a separate thread with the help of fine needle.

Broken pattern

Broken pattern : A broken pattern is the non continuity of a weave/ design/ pattern.

CAUSES : Wrong drawing in of threads. Incorrect shedding.


Broken Ends woven in a bunch

Broken ends woven in a bunch : This defect is caused by a bunch of broken ends woven into the fabric.

CAUSE : Failure of the weaver in attending the warp breaks properly.

MENDING: The broken ends woven in a bunch can be removed by using a plucker and the resulting loose ends should be cut with clipper. As a result, a bare patch occurs and combing in both directions with a metallic comb can fill this up.

Double end

Double end : When two or more ends gets woven as one. This defect is characterized by a thick bar running parallel to the warp.

CAUSES : Wrong drawing, taking more ends in heald eye.

MENDING: This fault can be corrected by pulling out the extra end with the help of needle. A bare patch is formed and can be filled by combing in both directions with the help of metallic comb.

Float

Float : Float is the improper interlacement of warp and weft threads over a certain area.

CAUSES : Improper sizing (ends sticking). Broken end entangling with the other ends.

MENDING: Only minor floats can be rectified. The floating threads are cut with a clipper . Combing in both direction rectifies the resultant patch.

Gout

Gout : Gout is a foreign matter accidently woven into the fabric.

CAUSES : Improper loom cleaning. Unclean environment.

MENDING: The extra foreign matter can be pulled out with a plucker. Combing in both direction rectifies the resultant patch.

Hole, Cut, Tear

Hole, Cut or Tear : This is self explanatory.

CAUSES : Sharp edges on cloth roll. Hard substance between layers of fabric in cloth roll. Course temples used for fine fabric. During removal of hard particles like, Iron particles

woven in the cloth.

MENDING: Non mendable.

Missing EndsMissing Ends : The fabric is characterised by a gap, parallel to the warp. The number of ends missing may be one or more.

CAUSES : Loom not equipped with warp stop motion. Dirty drop wires or accumulation of lint may prevent their

dropping. In electric warp stop motion, the electric bars are dirty or

corroded.

MENDING: When there are only two adjacent ends missing, the fault can be rectified by combing in both directions using a metallic comb. This may fill the bare patch formed due to missing ends.

Missing Picks

Missing Picks : A narrow streak running parallel with weft threads caused due to absense of weft.

CAUSES : Faulty let-off and take-up motion. Faulty weft-stop motion. Fell of the cloth not adjusted after loom stoppage for

mending.

MENDING: When there are only two adjacent picks missing, the fault can be rectified by combing in both directions using a metallic comb. This may fill the bare patch formed due to missing ends.

STITCHES

Stitches : A Single thread float.

CAUSES : Two adjacent ends sticking together during shedding for a

brief period of time. In case of synthetic yarns, ends sticking together due to

static charge during weaving.

MENDING: Stitches are cut with a clipper from both the ends. Combing in both the directions with the help of a metallic comb may rectify the resultant bare patch formed.

UNTRIMMED LOOSE THREADSUntrimmed loose threads : Any hanging threads on the face of the fabrics are termed as loose threads.

CAUSE : Tail ends not trimmed after piecing up.

MENDING: These defects can be easily rectified with the help of clipper.

WEFT BARWeft bar : An unwanted bar, running across the full width of a piece which differs in appearance from the adjacent normal fabric.

CAUSES : Difference in count, twist, colour, lustre. Faulty let-off and take-up motion.

MENDING: Non mendable .

SHUTTLE SMASH

Shuttle smash : Ruptued cloth structure characterised by many broken warp ends and floating picks.

CAUSES : Improper timing. Insufficient picking force. Slack ends in certain portion. The sagging ends obstructs

shuttle flight.


Lashing inLashing in : An extra piece of yarn woven into the fabric in the vicinity of the selvedge.

CAUSES : Defective setting of the shuttle box. Early or late picking. In case of auto loom, weft cutters worn out or not set

properly

MENDING: This defect can be corrected by pulling out the extra pick from the selvedge end, which can be clipped with the help of clipper. A bare patch is formed and can be filled by combing in both directions with the help of mettalic comb.

Oil Or Stain

Oil Or Other Stain: These are spot defects of oil, rust, grease or other stains found in the fabric.

CAUSES : Improper oiling/greasing of looms. Oil stained Take up roller.

MENDING: 1) Keep the stained portion of the fabric over an absorbent pad. Apply the

stain remover, wetting the stain and surrounding portion throughly.2) Rub gently to quicken the penetration of the stain remover.3) Rubbing should be done towards the centre of stain to avoid spreading.Note: Delicate fabric needs reduced pressure, otherwise, hole formation or

displacement of the fabric will occur.

Oily EndsOily Ends : These are oily warp ends.

CAUSES : Improper handling and storage of material in spinning

department. Oil-contaminated guides and oily hands during process of

warping. Improper handling of warp beams.




Oily WeftOily weft : These are oily weft picks.

CAUSES : Improper handling and storing in spinning department. Weft package falling on oily ground. Handling the weft with oily hands. Weft carring baskets having oil. Dropping of oil on weft package during oiling of the

winding machine.




Local Distortion

Local distortion : A Distortion occurs when there is displacement of warp and/or weft threads from their normal position.

CAUSES : The emery roll is worn out. In filament fabric having low reed picks.

MENDING: This defect can be corrected by combing in both directions using a mettalic comb.

SLOUGH OFF

Slough off : A slough-off is a bunch of weft woven into the fabric.

CAUSES : Improper winding of the yarn onto the weft pirn. Improper shape and size of the pirn. Harsh picking.

MENDING: The bulk yarn can be pulled out by means of plucker. Combing in both direction with help of mettalic comb can fill up the resultant bare patch.

Reed Marks

Reed Marks : A warp way crack caused by a damaged or defective reed.

CAUSES : Defective or damaged reed.


List of fabric defects in terry and velvet fabrics

• Broken pattern• Pile less spot• Uneven or loose piles

BROKEN PATTERN DUE TO DEFECTIVE PILES

Broken pattern due to defective piles : A broken pattern is the result of non-continuity of the design/pattern in the pile fabric.

CAUSES : Improper working of terry motion on loom. Improper functioning of jacquard. Missing pick.


PILE LESS SPOT

Pile less spot : It is a spot without the pile

CAUSES : Improper working of terry motion on loom. Improper functioning of jacquard.

MENDING: Non mendable

UNEVEN OR LOOSE PILES

Uneven or loose piles : In this type of defect there is variation in the pile height over the surface of the fabric.

CAUSES : Improper working of terry motion on loom. Improper functioning of jacquard. Missing pick.


List of fabric defects in Knitted fabrics

• Bariness• Bunching up• Drop stitch• Holes or Crack• Crack fall out• Horizontal srtipes• Verticle stripes

BARINESS

Bariness : A fabric defect characterized by textural bands or color bands in the course direction of a weft knitted fabric.

CAUSES : Use of irregular yarn having higher long term

irregularities. Using different count thread.


Bunching up

Bunching up : This is largely influnced by take-up mechanism and whether it functions properly or not.

CAUSES : Fabric take-up too weak. Thick place in yarn.


Drop stitchDrop stitch: Local column of dropped stitches.

CAUSES : Yarn guide not set poroperly (i.e yarn is not fed properly during loop

formation). Defective latch needle. yarn tension is not sufficient. Take-down is too high. Wrong yarn threading.

MENDING: This fault can be corrected by stitches reforming using a simple needle.

CAN BE AVOIDED BY: Precise yarn-guide setting. Needle change. Dial position readjustment. Use of fabric fault detector.

Holes or crackHoles or crack : Local holes obtained when yarn breaks during loop formation.

CAUSES : Relation between cylinder and dial loop not correct. Weak places in yarn, Which breaks during loop formation Knots. Yarn running tension is too high. CAN BE AVOIDED BY : Use of flat knots. Accurate yarn guide setting. Use of fabric fault detector. Use of yarn having lower hariness.

Cloth fall-out

Cloth fall-out : It is an area consisting of drop stitches lying side by side. Here the yarn is not stitched by several needles laying near to each other.

CAUSES : Yarn brakage. It can also occur after a drop stitch especially when an

empty needle with closed latch runs into yarn feeder and removes the yarn out of the hooks of following needles.


Horizontal stripes

Horizontal stripes : Are caused by uneveness in the courses. They traverse horizontally and repeat themselves regularly or irregularly.

CAUSES : Yarn feeder set badly. Differences in the yarn running-in tension. Jerky impulse from fabric take up .

Mending : Non mendable.

Verticle stripes

Verticle stripes : They can be observed as longitudnal gaps in the fabric. The space between adjacent wales is irregular.

CAUSES : Bent needles. Heavily running needles. Damaged latch needle. Damaged needle hook. Damaged dial or cylinder.

CAN BE AVOIDED BY : Needles and sinkers change after long time use. Use of fabric fault detector.

Inspection

Inspection : Inspection is the process of identifying and mending the defects. It is visual examination of fabric

REASONS WHY INSPECTION IS CARRIED OUT: To remove defects. To minimize the future reoccurrences of the defect. To determine quality and hence the price of the fabric. To supply information to proper levels of management

as to the qualities being produced.

Different Grading systems

1. 4 point system2. 6 point system3. 10 point system4. Graniteville system5. Dallas system

4 Point system

It is the most popular point system. It was published in 1959 by the National Association

of Shirt Pajama Sportswear Manufacturers. The 4-point system, also called the American

Apparel Manufacturers Association (AAMA) point grading system for determining fabric quality.

Faults are scored with penalty points of 1, 2, 3 and 4 according to the Size and significance of defect.

4 Point system

DEFECT SIZE PENALTY

3 inches or less 1 Point

Over 3 inches, but less than 6 2 Point

Over 6 inches, but less than 9 3 Point

Over 9 inches 4 Point

Points to be considered in 4 Point system

No more than 4 penalty points can be assigned for any single defect.

No linear yard or meter can contain more than 4 points, regardless of the number of defects within that yard or meter.

Each full width defect should assign 4 points. noticeable and severe defects are to be assigned 4 points for

each yard or meter in which they occur, regardless of size.

Advantages of 4 point system : Worker can easily understand it It has no width limitation

10 Point system

This system was developed in 1950’s and is the oldest method.

The system assigns penalty points to each defect depending on its length and whether it is in the warp (ends) or weft (fill) direction.

The Ten-Point System is somewhat complicated because points-per-length vary for warp and weft defects.

This method is still used by some manufacturers.

10 Point system

Warp defect Points Weft defect Points

Under 1” 1 Under 1” 1

1” - 5” 3 1” - 5” 3

5” - 10” 5 5” – ½ width of fabric 5

10”- 36” 10 Over ½ the width of fabric 10

Advantage of 10 point system: Mostly used in woven finished fabric. High accuracy

Disadvantage of 10 point system: It has width Limitation. Difficult in practical use.

Classification of Fabric after Grading

1) Fresh or first quality : fabric with no major or objectionable faults.

2) Second : cloth having minor defects.3) Fents : The cut pieces of cloths measuring 90cm and

more but less than 150 cm in length are graded as fents.

4) Rags : The cut pieces of cloths larger than 25cm but less than 90 cm are regarded as rags.

5) Chindies : These are the cloths having length of 25 cm or less.

Conclusions

• Due to presence of fabric defect, it has to be sold at lower prices, or even in some cases as seconds, which creates a hugh value loss to the company.

• To minimize value loss due to variety of defect occuring in the fabric, a manufacturer should try to minimize those defects by taking suitable remedies.

References• Textiles Committee, Ministry of Textiles, “A catalogue on woven

fabric defects and visual inspection”.• Circular Knitting (2nd edition) by Iyer , pp 236-239.• A project report on “ Comparision of yarn and fabric made from

CULTON® cotton and Regular cotton” under guidance of PROF. Manish pujari.

• K.L. Mak, P. Peng, K.F.C. Yiu,“Fabric defect detection using morphological filters” Image and Vision Computing vol 27, 2009, pp 1585-1586.

• Tamnun E Mursalin, Fajrana Zebin Eishita , Ahmed Ridwanul Islam,”Fabric defect inspection system using neural network and microcontroller” Journal of Theoretical and Applied Information Technology, vol 4, july 2008 pp 560-570.

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Fabric defects in woven and knitted fabric - hitesh choudhary