Monday, November 26, 2018

WOVEN FABRIC ANALYSIS ( ANALYSIS OF WOVEN FABRIC

FABRIC ANALYSIS

"Fabric analyses is a process to know about all information required to start manufacturing of a fabric". A weaver always requires to analyse the fabric to be woven in a systematic manner. Weaver should determine all the fabric parameters precisely. "Any negligence during fabric analysis can cause heavy to a very heavy loss to the weaver". The proper and precise analyses of fabric should be conducted before starting the fabric production. The correct procedure of fabric analysis is given below:

Step 1 – identification of warp and weft directions:

The warp and weft directions of the fabric are the most important factors for any weaver. The warp and weft direction in the fabric is identified carefully. The direction of warp and weft is identified as follows:

Dent mark in the fabric:

This is the best way to identify the warp and weft direction in the woven fabric. The fabric is observed under a light source. The dent mark in the grey fabric can be observed clearly through naked eyes. "The dent mark is the airspace which is created due to dent wire of the reed in the fabric". This airspace appears in the fabric at regular interval of the distance ( according to denting order used in the fabric). These dent marks run in the warp direction in the fabric.



 Thus the weaver decides the warp direction in the fabric to be woven. The other fabric direction is weft direction.

If a weaver receives a dyed fabric swatch, then some difficulties come during identification of warp and weft direction. Difficulties increase more if the fabric has higher warp and weft density in the fabric. In this situation, the dent marks do not appear clearly and continuously. Now the fabric is observed carefully with the help of a magnifying glass. Uneven airspace along warp direction due to dent wire of the reed can be identified clearly and warp and weft direction can be decided in the fabric.

In some fabrics, the one end per dent is passed through the reed. In this type of fabric almost even air gap between two ends results and hence the dent mark does not appear clearly in the fabric. In this kind of situation, the technician needs extra care to see uneven airspace between two adjacent ends. "As soon as fabric comes out of take-up roller, its width tends to shrink. The ends come closer to each other but an uneven end to end airspace generates during shrinkage".
Please note that picks look more straight than an end in the fabric.

Following are the few helping factors in making the decision of the direction of warp and weft of the given fabric swatch:

Ends per inch and picks per inch:

Ends per inch and picks per inch always do not help to identify the warp and weft direction but in maximum fabrics, the ends per inch are kept higher than picks per inch. There are two reasons which insist a weaver to keep EPI higher than PPI. The first reason is the cost of production. Higher PPI causes a direct increase in weaving cost of the fabric. The second reason is the widthwise shrinkage of the fabric during weaving. In plain fabrics, the ratio of warp and weft in the plain fabric is kept at 55:45. This warp and weft ratio gives the best results in terms of efficiency, productivity, and quality. As the warp and weft ratio starts to become equal, the widthwise fabric shrinkage during weaving increases. This increased shrinkage causes increased warp breakage rate on both the selvedge sides. The fabric also starts to tear at both the selvedge during weaving. In this way, the weaver can decide the warp and weft direction.

Warp and weft crimp:

The warp crimp and weft crimp also help to decide the warp and weft direction in the fabric swatch. "In any grey fabric, the warp crimp is always more than weft crimp". The weaver can make his decision with the help of warp and weft.

Type of yarn used in the fabric:

In some fabric, single ply and double plies yarn are used together. One type of yarn is used in warp and another type of yarn is used weft. In this kind of fabrics, weaver always prefers double plies yarn in the warp because sizing cost does not involve in double plies warp yarn.

Step 2 determination of ends per inch and picks per inch:

These parameters can be determined easily with the help of counting glass in most of the fabric. "The counting should be carried out under sufficient light source. The opposite colour background should always be there under the fabric swatch". This opposite colour background under the swatch helps to increase the contrast between airspace and yarn. 



A technician becomes able to see and count the EPI and PPI easily. The technician should always count the ends or picks in complete one inch. Some technicians use half an inch or quarter inch to count ends or picks. This practice does not give an accurate result.

"In some fabrics like twill and satin having a higher number of threads per square inch, the counting of ends or picks becomes much difficult for the technician. In these kinds of fabrics, the ends per inch and picks per inch are determined accurately with the help of weave repeat".

In some fabrics, the ends or picks are overlapped to each other. In these types of fabric, the one-inch fabric is opened and ends or picks are counted.

Step  3 determination of GSM of the fabric:

The way to determine the GSM of the fabric is adopted as per the availability of size of fabric swatch. Sometimes fabric swatch is very small. Cutting of required circle does not become possible. The GSM of the fabric is found by adopting another method. The methods of determination of GSM are given below:

By using GSM cutter:  
if the fabric swatch has sufficient size, then a disc of fabric is cut with the help of round cutter. This disc of the fabric is weighed on the weighing scale. 

GSM  =  Weight of fabric disc ( grams ) x 100



Now a question may arise why do w uhe multiply the circle weight with 100.  This is just because of the area of the fabric circle. We can obtain 100 fabric circles of the same size from one square meter of the fabric. Since we find the weight of one circle, therefore we multiply the circle weight with 100 to find the weight of one square meter of the fabric.



Without using GSM cutter: 

if the fabric swatch does not have a suitable size for cutting the disc then the fabric swatch is cut in a rectangle shape. "The length and width of the fabric swatch are measured in centimeters". See below graphic.



Now GSM of the fabric is determined by using the following formula:  

To find the GSM without cutting the fabric:

many times your buyer does not allow you to cut the fabric. In this kind of situation, the length, width and the weight of the piece are measured accurately and GSM of the fabric is calculated with the help of following formula:



Step 4 determination of warp count and weft count:

The warp and weft count of the fabric should be determined precisely. The warp or weft yarn is taken out from the fabric. The length of the yarn is measured in the meters and its weight is measured in the grams. Now technician can calculate the count of warp or weft yarn by using the following formula:


Step 5 determination of the degree of twist in the warp and weft yarn and twist direction:

The degree of the twist is a very important parameter of the yarn because the yarn twist directly affects many fabric properties. The yarn twist should be analysed properly to achieve the same fabric properties as per sample. TPI and direction of twist both should be checked by a weaver before purchasing the yarn. If a weaver does not have an in-house testing facility, he should arrange the same from outside laboratory.



Step 6 determination of warp and weft crimp:

Warp crimp: 

Warp crimp (regain) is the ratio of the difference between warp length and fabric length to fabric length in the term of % is called warp regain.


If we have the fabric swatch, we can determine the warp crimp ( regain) by using below formula:



Weft crimp: 

It is the ratio of difference (between straightened pick length and fabric width) to fabric width expressed in the term of percentage is called weft crimp. This term may also know as weft regain.



 The weft crimp can be obtained by using below formula:




 Step 7 Warp and weft pattern:  

If there is multicolour yarn in the warp or weft, then weaver needs to analyse the warp and weft pattern correctly. Since warp pattern is set in warping, therefore warp pattern analyses requires extra care during analyses. A little mistake in warp pattern may be a cause of heavy loss to a weaver. The pattern mistake in the warp cannot be recovered by a weaver in any way. Complete fabric will get rejected.

Weaver should always keep in mind that warp pattern mistake is unrepairable damage in weaving.

Step 8 weave of the fabric:  

The weave of the fabric is a very important parameter of the fabric. The weave, draft and peg plan of the fabric should be analysed properly and correctly. The draft decides the number of heald shafts to be used in the loom to weave a particular fabric. The peg plan defines the lifting order of heald shafts.

Please note that any mistake during draft analyses requires re-drawing of the warp. It causes productivity loss to the weaver.

Step 9 fabric selvedge: 

Sometimes the type of selvedge becomes very important fabric parameter because it influences the cost of the product up to some extent.

Step 10 contents and blend percentage:

A weaver should always conduct a test of contents of warp and weft yarn. If the yarn is blended of two fibres, the blend % should also be tested.

                                THE END


You may also interested in following articles:


Reed count selection in weaving


Fabric parameters or fabric specifications


Reed's specifications and dent's wire thickness calculation


Sizing calculations


Cotton yarn diameter, cotton yarn diameter formula

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4 comments:

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