FABRICS DEFECTS:-

FABRICS DEFECTS:-

Classification of Cloth Fault:-

More imperfections or fault in cloth occur while it is woven in the loom. Some of these defects are visible, while others are not: again, some defects may be rectified during and after weaving, while others are not . However , fabric defects or cloth faults , as they are commonly termed , are classified as:-

(A) Warp defects.

(B) Weft defects, and

(C) Cloth Faults -

(A) WARP DEFECTS:-

The following are the most common warp fefects in cloths:

(1) Warp Breakages or Broken Ends, 

(2) Wrong ends, 

(3) Selvedge Defects.

(4) Stitching, and 

(5) Floats.

(1) Warp Breakages or Broken Ends :-

The cause of warp breakages during weaving are;-

(i) Weakness, and

(ii) Violence. 

A break occurs whenever the warp tension exceeds the yarn strength. Again , the end breakage rates in fabric vary with changes in yarn strength, tension etc , and with good or bad working looms.

The main places of warp breakages are:- 

(a) Back shed.

(b) Healds.

(c) Front Shed.

(d) Reed, and

(e) Shuttle.

(a) Back shed.

The Cause oo warp threads breaking in the back shed are : Inadequate or over sizing , defective lease rod negative brake , motion and improper setting of back rest.

(b) Healds.

The causes of warp breakages at Healds in the centre of the shed are : Uneven varnishing and limps of varnish sticking to heald eyes not deep enough , higher count of healds used than required,wider or narrower warp than the width of healds improper setting of healds and wrong timing . 

(c) Front shed.

The causes of warp breakages at the front shed are: Bigger depth of shed , heavy sized warp , hard vop, unpolished and worn shuttle.

(d) Reed.

Rusty reed , parts of sizes accumulating on the reed, shuttle tongues working at the back of the shuttle , fibrous warp and chafing by reed causes warp breakages at reed .

(e) Shuttle.

The damage to warp by wrong fittings of shuttle and by worn shuttle is considerable. Shuttles should run evenly over the sley race to minimise warp breakages. 

Other causes of end breakages are:- 

Thick knots, unequal tension on warp , constant vibration in suitable atmosphere, poor yarn quality of and bad warping and beaming are also the causes of ends breaking during weaving.

(f) Shiner.

In rayon and silk weaving, uneven tension on the warp threads, that is, tight and slack ends causes serious defects in fabrics in addition to end breakages . Tight ends show up as bright streaks called 'shiner' in rayon fabrics.

(2) Wrong Ends.

When more than one end breaks at the same time , there is a possibility that they may be drawn through wrong healds . The defect is more prominent in plain weaves than the others.

The other defect found in fancy fabrics is the crossing of differently coloured ends at the time of piecing-up , causing wrong design produced on the clothd.

(3) Selvedge Defects.

The general impression of s cloth is mostly formed from the appearance of its selvedges. Selvedges must be strong enough to withstand the tension of the finishing processes.

(1) (i) If the selvedge weave differ from that of body and two designs do not harmonise , rough, ‘curly or wavy selvedge ' will follow . Curly or wavy selvedges may also be caused by unequal tension put upon the ground and selvedge ends either in the warping and sizing machines or in the loom. A curly or wavy selvedge is one of irregular width.

(ii) 'Waviness of selvedge 'generally occurs in the off-side of a width loom weaving narrow fabrics, on account of long length of weft being between the selvedge and the shuttle box.

(iii) Too strong temples may also cause curly or wavy selvedge. This defect may be remedied by adjusting the position of the temple and the selvedge and buy allowing the selvedge to run at a little oblique. Tension of ground and selvedge ends must always remains uniform to minimise Selvedge defects. 

(2) 'Weft breakages or cuts ' at the selvedges may be due to : wrong drafting or denting , wrong timing of Selvedge motion , damaged or rusty reed , uneven tensioning , or ends running oblique.

(3) 'Corded selvedge ' are caused due to wrong drawing of selvedge threads and get nipped in the calender machine and cause tears in the piece.

(4) 'Small or big loops' in the selvedges are formed by insufficient tension in weft winding, by shuttle rebounding, and by strong picking. If the loops are very big, they are drawn inside the shed in the next pick causing ' corded selvedge’. 

(5) Again faulty temples cause 'streaks' at one or both sides , and faulty centre weft fork causes 'streaks' in the centre of the fabrics . 

(6) If the teeth of temples are long, they cannot freely liberate the cloth without showing 'temple marks’. Ring temples may injure the selvedges of delicate fabrics , and if rings becomes clogged they will tear the cloth . Ring temples with a single ring act on the selvedge only. Simple ring temples are for dress goods, velventeens and light fustians that would be injured by 'temple marks' showing in the body of the fabrics . 

(4) Stitching:

It is a major defect particularly in good quality cloth . There are both 'warp and weft stitching '. It is common fault in which the ends and the picks are not interlaced according to correct order of pattern.

(1) When a dobby peg is broken or bruised a ' warp stitching defect becomes prominent. Sometimes it becomes difficult to distinguish between warp and weft stitches.

(2) To remedy warp stitching defect, crank should be taken on the back centre and it should be examined that the depth of all sheds in the pattern are sufficient for easy passage of the shuttle. If the shed and pick ate properly timed, and the shuttle, shuttle box and picker are properly attend to, most cases of stitching defects will disappear.

(3) Cord and leather connections above and below healds , flossy and undersized warp are the other causes of 'warp stitching '. 'Stitching' is again responsible for warp breakages , shuttle flying-out heavy rejection of cloth.

(5) Floats.

The defective action of the centre weft motion causes the fork to catch the warp and warp and the weft forming 'loops or floats in cloth’.

Entangled warp ends, lints superfluous yarn, or broken reed wire, and proper sizing may also cause 'warp floats’.

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