Textile Spinning, Weaving and Designing by M. G. Mahadevan

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Textile Spinning, Weaving and Designing
By M. G. Mahadevan
Textile Spinning, Weaving and Designing

CONTENTS
1. Basic Aspects of Textile Fibers 1
2. Structure and Properties of Textile Fiber 19
3. Spinning Diagnosis 30
4. Theoretical Basis of Spinning 53
5. Spinning Methodology 65
6. Textile Weaving 163
7. Braiding Processes 201
8. Designing Mechatronics 231
9. Textile Industry in India 269

One
Basic Aspects of Textile Fibres

The word fibre creates a mental picture of a long, thin. hairlike objects and indeed textile fibres are like that in general physical shape.Not all fibres though are suitable for textile purposes because a textile fibre must possess sufficient length. fineness, strength and flexibility to be suitable for manufacture into fabrics. It will be seen later on now they vary in these respects and how the variations are responsible for the differing character of materials. It will be seen also that this definition can apply both to natural and to man-made fibres.

Filament and staple
'Filament' and 'staple' are two terms represent the two basic forms of textile fibres. Filament is the name given to a fibre of continuous length, that is to say it is long enough to be used in a fabric without increasing its length by adding other fibres on to it. An example of a natural filament is silk; the cocoon of a silk-worm can contain about two miles of continuous twin filaments. Man-made filaments produced by spinning machines can be many miles long. Staple is the name given to fibres of limited length. To make a continuous length of yarn, staple fibres have to be twisted together. Staple fibres can range from about one-quarter of an inch to many inches in length, but in no case do they ever become long enough to be classed as filament, so the two terms are quite separate except for the fact that man-made filaments can be converted into staple fibres by deliberately cutting them into short lengths. This is a very common way of processing man-made fibres, but the reverse process is never carried out. An example of a natural staple fibre is cotton.

Yarn
A yarn can consist of either staple fibres, or of filaments put together. Filaments merely need grouping in order to produce the thickness of yarn required, the length is already there in the individual filaments. Grouping of filaments is achieved by twisting them together. The twist, usually quite a small amount, merely serves to keep to filaments reasonably together. Staple fibres have to be twisted to make them cohere into a continuous length of yarn.

The action of twisting forces the fibre surfaces into contact with each other setting up friction between them which enables a lengthwise tension of the yarn to be resisted. In this way a continuous length of yarn can be made even from very short fibres.

The type of yarn exerts a strong influence on the texture and appearance of the fabric. In general. filament yarns are thin, smooth and lustrous and staple fibre yarns are thicker, fibrous and non-lustrous. An excellent example of these different characteristics can be seen by comparing the fibrous nature of the outer wool fabric of a coat or suit jacket with the smooth lustrous surface of the lining of the garment.

Fabrics
Most fabrics are made from yarns.


Woven fabrics
In their simple form these consist of two series of threads, warp and weft, interlaced at right angles to each other. The warp threads run the length of the fabric and the weft threads run across the width of the fabric. The edge at each long side of a woven fabric is called the selvedge and it is commonly of a different construction or appearance, to the rest of the rest of the fabric because its function is not only to provide a firm neat edge 'finish to the fabric for the sake of appearance. but also to provide a secure grip for finishing machinery. For this latter reason, small regular groups of pin-holes can often be seen in a fabric selvedge showing where it was held by the machine pine. Other types of machine use clips which do not mark the selvedges. The section drawings at the side and the bottom of the plan show that warp and waft interlace with each other in a similar manner.

If the threads are closely spaced it can be seen that this form of interlacing gives a very tight structure because the alternate interlacings give no room for sideways movement of the threads. The draping properties of such a structure would depend entirely on the flexibility of the fibres and yarns. For example, a square of wire gauze, as used in a laboratory, is formed by interlacing steel wire in plain weave. As a result a fairly rigid piece of fabric is produced which is the intention. This fabric is too rigid to be used for any normal fabric purpose because steel wire is far less flexible than any textile fibre or yarn.

A fine cotton calico can be made by interlacing cotton yarns in plain weave much more closely than the wire gauze, but because of the softness and flexibility of the cotton, the resulting fabric is quite supple and is flexible enough for many fabric rurposes. The toile used by dressmakers for making preliminary models of dresses is often calico of this type.

Woven structures can vary in density and in interlacing, and this can make them differ in appearance and handle, but in their simple forms they represent a very stable material. By this it is meant that unless a woven fabric is deliberately made otherwise (such as in a 'stretch' fabric) it does not extend a great deal in warp and weft directions because of the interlacings-which resist an attempt to pull warp or weft straight.

The natural elasticity of the material will produce a reasonable amount of 'give' in warp or weft directions. This will very according to the tightness of the structure and the amount of elasticity in fibre and yarn. The amount of movement is usually small enough to ensure that a piece of woven fabric cut to shape, as part of a garment is not too easily distorted, but yet in wear it will 'give' enough to be comfortable if the garment is cut and styled properly. If tension is exerted diagonally much more movement is obtained because the force is not now directly along a yarn direction but is pulling across both series of threads causing a 'scissor' action. This diagonal direction is known as bias.

True bias is an angle of 45°, i.e. exactly between warp 5lnd weft, and smaller angles of bias can be used if necessary, but the greatest amount of movement is along the true bias line. In using a woven fabric for clothing, due regard must be paid to the grain of the fabric. The grain is represented by warp and weft. If the fabric is true, the warp runs straight lengthways and the weft runs across the fabric at 90° to the warp. Garments are usually made up so that the warp runs vertically down the garment as it is worn and the weft horizontally across it.


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