FABRIC DEFECTS:-

FABRIC DEFECTS:-

In first portions the warp defects are explained, now here the weft defects are discussed in details; 

(B) WEFT DEFECTS;-

The important weft defect in cloths are the following:-

(1) Weft breakages and mispicks or broken or broken pattern, 

(2) Bareness or thin and thick places. 

(3) Tight Picks.

(4) Picks out.

(5) Weft curling.

(6) Slugs and cracks.

(7) Shuttle marks.

(8) Black picks , and

(9) Tear Drops.

(1) Weft Breakages and Mispick:-

(a) Some of the cause of weft breakages are ad follows: Tender yarns , soft-nosed bobbins , broken cops, snarls, weft cutting in the box, harsh , picking , temples set too near the reed , improper packing if cops, cracked shuttle, defective weft winding. 

(b) Weft breakages may occur if the shuttle spindle is too slack and vibrate vertically, or the drag on weft is too severe , or shuttle bottom is worn.

(c) When a pick breaks ,or when the weft is exhausted extending partly across the shed , the loom should be stopped immediately: but owing to faulty action of the weft fork motion, the loom may make one or two picks more before it stops . This causes 'mis pick' or thin place in the fabric.

(d) A 'mispick' may also occur on the weaver starting a loom with shuttle in the wrong box .

(e) A ‘mispick or broken pick' is most detrimental in fancy and coloured goods twill , sateen , venetian and similar weaves , as it will spoil the appearance of cloth. In all these cases , weavers must be alert for pick finding to avoid mispicks. Agai, when a pick is effective through a wrong division of warp threads due to defect in dobby pegs or dobby motion, the fault in the cloth is known as 'wrong pick’, though it looks like a 'mispick’.

(2) Bareness or Thin and Thick Places:-

(1) These defects in fabric either due to loom faults or due to weaver’s carelessness. A thin places is made in the cloth while the take-up motion takes two teeth instead of one tooth in the ratchet. This happens owing to irregular travel of the push-up or driving catch being set higher , or some parts worn out , or one or more teeth in the ratchet wheel being shorter in length than others.

(2) Loose bearing or the sley or crank shaft, and loose reed or loose crank arm in the sley , and irregular let-off may cause thin places in cloth.

(3) 'Thick places' or 'weft bars' in cloth are made of weft being unduly crowded due to take-up motion missing and failing to turn the cloth roller. Sometimes pushing-up or driving catch cannot engage with a tooth of the rack wheel, or driving catch slipping over the rack wheel, thereby making thick places or 'weft bars' in the fabric. A gear wheel slipping out of mesh , the ratchet wheel slipping on its shaft, and the beam wheel slipping on its shaft will make thick places. 

(4) Another probable cause of 'weft bars’is that the cloth roller is not properly gripping the cloth forward with it as it rotates, owing to perforated covering being worn ,or it is unsuitable for fabric.

(5) Uneven tension on warp threads either at side or in the middle of the shed, or uneven tension of cloth roller results 'thick places' and unevenness in cloth. Thin and thick fabrics are sometimes termed 'uneven cloth ' or ‘shady pieces’.

(6) An uneven cloth generally refers to a 'bare cloth' in which the counts of reed and the number of picks per inch or 2.54 cm. vary , or yarns of uneven diameter are used. An uneven cloth is caused by weaver’s beam not turning freely by let-off chain and weight sticking, by back rest moving irregularly by loose cranks arm by vibration of loom, by uneven shedding , or by driving belt clumsily placed.

(3) Tight Picks:-

The tight picks in a cloth are caused if the cops are wound too tightly . In the subsequent finished processes , these picks are stretched, and in rayon and nylon fabrics they form 'shiner’.

Tight picks Aldo cause the cloth to curl and put undue tension to the shuttle. Irregular take-up and let-off motions may also cause tight and loose places. 

(4) Picks Out.

It becomes sometimes necessary to pick out certain length of weft , and after doing so, the warp is to be drawn back before restarting the loom . If it is not so done , bad 'starting places' will become prominent in the fabrics.

(5) Weft Curling.

The weft curling is caused by inserting highly twisted weft yarn, or weft running too freely or irregularly through the shed , or shuttle rebounding. In all these cases 'curls,’ or 'snarl' or 'loops' appear on the surface of the fabrics. The twisted weft must, therefore be conditioned or steamed before use to set the twist to avoid wrgt curling defect.

KINKY FABRICS.

The places in the fabric were slack strands have twisted on themselves, forming loops in the yarns, are called 'kinky fabric ' . A 'kinky weft' is also found in cloth as short thick places running weft wise in which small loops in the weft yarn are placed at irregular intervals. The weft yarn may be looped and twisted , and the causes are too much twists in yarns, and in sufficient shuttle tension, improper build of cops , pirns or bobbins, bounce shuttle, and improper conditioning. 

Pulled in Weft.

It is a loop of weft pulled into the fabric at the selvedge. It may be due to shuttle catching weft while entering the shed , improper boxing of the shuttle, failure of weft feeler knife to cut and hold the weft, picker not properly adjusted , weaving in the side weft fork. 

(6) Slugs.

(1) When the weft yarn is unclean and contains slubs and it’s diameter is irregular, the defect appearing on the cloth is known as ‘slugs’ . In other words , the abruptly thickened place in the yarn , ir a bunch of lint entangled in the yarn or fabric, is called 'slugs’.

(2) Slugs may also be caused by a adhere fibres or lint to the weft and get caught in the shed . Little balls of fibres or lint in warp threads caused by improper sizing and by friction of healds appear like weft slugs.

(3) Other causes of slugs are: soft pirns , shuttle rebounding in the box, shuttle tension working jerkily, rough pickers, and obstruction on sley between selvedge and shuttle box.

CRACKS:-

(1) 'Cracks' are visible in cloth when an open streak or irregular stripe , parallel with the weft , extends partly or fully across the fabric.

(2) When certain parts of the sley get worn out , it gives erratic movement, causing the cloth strained at same places resulting 'cracks' in fabrics. This becomes more prominent in artificial fibres, such as rayon, acetate , synthetic fibers etc.

(3) The cause of 'cracks' in cloths are loom banging-off, loose crank shaft and crankshaft beating , bad rocking shaft bearings, improper let-off, too much warp wise play in reed and clutch not grabbing properly.

(7) Shuttle Marks and Starting Places:-

(a) (i) The 'shuttle mark' is visible in cloth as a fine line parallel with the weft due to injury of a group of adjoining warp ends. When the movement of the shuttle is mot even due to imperfect alignment of the boxes or for any other reason, shuttle marks are seen in the fabric.

(ii) In cases of delicate warp yarns , susceptible to chafing and bruising a 'shuttle mark’in the direction of weft is visible.

(iii) Other causes of shuttle marks are: bottom shed line too high , shed opening too low , shuttle mot flying straight, and shuttle entering the shed too early or too late.

(b) The faults known ad 'starting places’in cloth are caused as a result of stopping and starting a loom , or restarting as in the Hattersley shuttle-changer in weaving in finer qualities of fabrics as, rayon crepes, taffetas etc.

SET MARKS:-

It is a horizontal mark across the cloth in which there are an abnormal number of picks per inch or 2.54 cm. 

The causes of set marks may be attributed to:- failure to let cloth back the correct distance after a pick-out or after loom banging-off, change in humidity in the weaving shed , crossed warp ends , loose eccentric pin, faulty take-up and let-off motions , and lapse on beam.

(8) Black Picks:-

Certain fabric even after finishing stand useless owing to the presence of ‘stained weft' or 'black picks’.

The causes of black picka, oil stains, or other stained weft are: oil getting in shuttle box , oily or dirty picking band , picker , shuttle or shuttle box: weft touching the oily spindle , buffer or check strap: weft ballooning: shuttle running crooked and shuttle worn out . The fault of oil stains may sometimes to the be attributed to the spinning and to the preparatory departments. 

GOUT.

It is a defect arising out of foreign matter woven in a cloth accidently, unusually lint or waste or material.

(9) Tear Drops.

The 'tear drop' are characterised by short elliptical deviation of one or more adjoining picks. These are more pronounced in taffetas and gross grain weaves . Exactly like shuttle marks this defect is also caused due to a few warp ends being slack, or then a few ends tight sticking together, and suddenly released ,resulting tear drops.

(C) Cloth Defects:-

The defects pertaining to warp and weft in cloth have been classified as 'warp and weft faults’. Other faults , that occur during weaving in the loom , are termed 'cloth fault’. Cloth faults are identified and marked , and the goods are classified in the cloth inspection room according to the number and extent of defects. The 'cloth defects' are classified as:-

(1) Oil spot, 

(2) Dirty cloth, 

(3) Hairy or flossy cloth,

(4) Rough surface cloth, and

(5) Harness skips.

(1) Oil Spot.

Oil spot on fabric are caused by too much oiling on loom parts , or from other sources. Yarns may also contact oil stains in the spinning and in the Preparatory departments. However, oil stains in most fabrics may be removed by scouring.

(2) Dirty cloth.

From spinning to yarn preparation, and from preparation to weaving department, there are many machines and workers to handle yarns and fabrics . Cleanliness is more important in rayon and other synthetic fabrics, and those cloths that are sold directly from looms to the consumers. But it is less important in cotton and woollen goods as they scoured and finished before marketing.

(3) Hairy or floss or fuzzy cloth.

(i) 'Flossy , fuzzy or hairy cloth' apply to the quality of cloth in which the fibres in the yarns have been roughened , cut or broken , either before, during or after weaving. Matka , kete or hand spun yarns , filament and spun yarns , uneven and fibrous yarns contact this defect easily.

(ii) Rusted and damaged reed wires , rough drop wires and badly varnished healds cause hairy cloth’owing to abrasion of the warp ends as the cloth is being woven . Unsized yarns and too low bottom line of shed will also cause hairy or flossy cloth.

(iii) Sometimes harsh or roughened sand roller cause the fabric abraded and bruised . Hence , for weaving worsted or other delicate fabrics , cloth rollers composed of rubber , cork and of other special construction ate being found favour in the industry in recent years.

(4) Rough Surface Cloth :- 

(i) Rough surface fabrics ‘ are due to improper tension of weft yarn , wild weft yarn , or unsteamed weft yarn .

(ii) They are also due to varying tension of warp ends resulting from wrong timing of healds motions , insufficient tension in cop , and Shuttle rebounding.

Weft tension in shuttle may be increased by using furs, or strips of leather on the sides of the shuttle . Shuttle rebounding may be remedied by decreasing the force of a pick or by decreasing the voltage of power supply.

(5) Harness Skips;-

Specially by dobby looms, wrong pattern chains and athor causes are responsible for harness skips. 

There are several other cloth defects caused out side the weaving shed . The weavers or the loom jobbers cannot be certainly held responsible for following defects, viz, tender warp , badly sized or oversized warp , uneven yarn, large knots in ends and cops.

 These fault occur in the spinning and in the Preparatory departments.

Faults in Rayon Fabrics:-

The woven rayon has similar faults to other yarns , but some faults are it’s own . Rayon is a sensitive yarn. It is subject to minimum amount of friction and stretching, but spun rayon has more latitude than filament rayon.

The chief faults in Rayon fabric are the following: -

(1) Barry places , or thin and thick places, or weft bars;

(2) Bright pick.

(3) Broken threads;

(4) Button: 

These are made by chafing with rough reed, ot threads too low on shuttle race, or worn healds, or the broken filaments being pushed back by the reed;

(5) Cracks;

(6) Cockled places;

(7) Creases;

(8) Curls;

(9) Picks missing; 

(10) Reed Marks;

(11) Set-up or starting places; 

(12) Selvedge Faults.

(13) Shuttle marks ; 

(14) Snarls;

(15) Trailing-in:- 

When right and left twist weft yarns are used , these must be kept separated between the mouth of shuttle box and the selvedge: and 

(16) Wrong Pattern:-

When bunch of warp breaks due entangled shed or shuttle trap, the repairing of warp may cause wrong pattern.

Ref:-Weaving Mechanism Book Vol. II by Prof. N. N. Banerjee.