Saturday, May 2, 2015

From Fiber to Yarn: Conventional Yarn Spinning – Part II[1]
Art Resource

Marie-Therese Wisniowski

Preamble
This is the thirty-ninth post in the "Art Resource" series, specifically aimed to construct an appropriate knowledge base in order to develop an artistic voice in ArtCloth.

Other posts in this series are:
Glossary of Terms
Units Used in Dyeing and Printing of Fabrics
Occupational, Health & Safety
A Brief History of Color
The Nature of Color
Psychology of Color
Color Schemes
The Naming of Colors
The Munsell Color Classification System
Methuen Color Index and Classification System
The CIE System
Pantone - A Modern Color Classification System
Optical Properties of Fiber Materials
General Properties of Fiber Polymers and Fibers - Part I
General Properties of Fiber Polymers and Fibers - Part II
General Properties of Fiber Polymers and Fibers - Part III
General Properties of Fiber Polymers and Fibers - Part IV
General Properties of Fiber Polymers and Fibers - Part V
Protein Fibers - Wool
Protein Fibers - Speciality Hair Fibers
Protein Fibers - Silk
Protein Fibers - Wool versus Silk
Timelines of Fabrics, Dyes and Other Stuff
Cellulosic Fibers (Natural) - Cotton
Cellulosic Fibers (Natural) - Linen
Other Natural Cellulosic Fibers
General Overview of Man-Made Fibers
Man-Made Cellulosic Fibers - Viscose
Man-Made Cellulosic Fibers - Esters
Man-Made Synthetic Fibers - Nylon
Man-Made Synthetic Fibers - Polyester
Man-Made Synthetic Fibers - Acrylic and Modacrylic
Man-Made Synthetic Fibers - Olefins
Man-Made Synthetic Fibers - Elastomers
Man-Made Synthetic Fibers - Mineral Fibers
Man Made Fibers - Other Textile Fibers
Fiber Blends
From Fiber to Yarn: Overview - Part I
From Fiber to Yarn: Overview - Part II
Melt-Spun Fibers
Characteristics of Filament Yarn
Yarn Classification
Direct Spun Yarns
Textured Filament Yarns
Fabric Construction - Felt
Fabric Construction - Nonwoven fabrics
A Fashion Data Base
Fabric Construction - Leather
Fabric Construction - Films
Glossary of Colors, Dyes, Inks, Pigments and Resins
Fabric Construction – Foams and Poromeric Material
Knitting
Hosiery
Glossary of Fabrics, Fibers, Finishes, Garments and Yarns
Weaving and the Loom
Similarities and Differences in Woven Fabrics
The Three Basic Weaves - Plain Weave (Part I)
The Three Basic Weaves - Plain Weave (Part II)
The Three Basic Weaves - Twill Weave
The Three Basic Weaves - Satin Weave
Figured Weaves - Leno Weave
Figured Weaves – Piqué Weave
Figured Fabrics
Glossary of Art, Artists, Art Motifs and Art Movements
Crêpe Fabrics
Crêpe Effect Fabrics
Pile Fabrics - General
Woven Pile Fabrics
Chenille Yarn and Tufted Pile Fabrics

The Glossary of Terms, Timelines of Fabrics, Dyes and Other Stuff, A Fashion Data Base, Glossary of Colors, Dyes, Inks, Pigments and Resins, Glossary of Fabrics, Fibers, Finishes, Garments and Yarns and Glossary of Art, Artists, Art Motifs and Art Movements have been updated in order to better inform your art practice.

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Introduction
Yarn is a generic name for an assemblage of fibers that are laid or twisted together. Yarns are classified as: (i) spun yarns, made of staple fiber; (ii) continuous filament yarns made of filament fiber.

Two cotton fabrics can have significantly different fabric characteristics due the yarn structure (i.e. its weave). The yarn can enhance good fiber performance or can compensate for poor fiber performance. The structure of the yarn is an important factor in a finish such as napping or it may determine the effectiveness of finishes such as the Schreiner finish for luster of sateen fabrics.

While some fabrics have a basic calendered finish this cotton sateen fabric has been specially finished using the Schreiner technique.

Some fabrics characteristics that are related to the nature of the yarn are:
1. Texture – smoothness, softness, crepiness etc.
2. Beauty – luster, dullness, slubbiness etc.
3. Weight – sheer, medium, suiting etc.
4. Comfort – warmth, coolness, absorbency etc.
5. Performance – resistency, pilling, soiling etc.

Spinning is the term applied to the processes of making yarn. Spun yarns are made by computer controlled mechanical spinning of natural or man-made staple fiber. Continuous filament tow and yarn are produced by chemical spinning (see future post) – the extrusion of a solution through a spinneret. The chart below gives a layout of the procedures involved for these two major spinning processes.

Diagram of yarn spinning process.
Courtesy reference [1].


Computer Controlled Mechanical Spinning
Computer controlled mechanical spinning consists of a series of operations designed to clean and make parallel staple fibers in order to draw them out into a fine strand and twist them into a spun yarn. Mechanical spinning is one of the oldest manufacturing processes and as been described as an invention as significant as that of the wheel.

The earliest primitive spinning consisted of simply twisting fibers between fingers. Later primitive man bound the fibers to a stick call a distaff, which was held under the arm leaving the fingers free to draw out the fibers.

The use of a distaff to create spun yarn.

When the strand was about a yard long, the free end was fastened to a rock and spindle, which had enough weight to help draw out fibers and could be spun like a top to twist the yarn.

This method was satisfactory for spinning wool and flax, but primitive man found that the weight of the spindle was too great for the shorter, less cohesive cotton. A small spindle set in a bowl with a little water made cotton fibers moist and cohesive and relieved them of some of the weight of the spindle. Thus primitive spinners varied the spinning process according to characteristics of the fiber to be spun and so developed two spinning processes - the intermittent twisting and winding of the wool fiber, which is comparable to the mule-spinning of wool as used today, and the continuous twisting and winding of cotton yarn, which is comparable to the continuous ring-spinning of the modern era cotton spinning mill.

The spinning wheel was developed by the spinners of India, who turned the spindle in a horizontal position and attached it to a wheel, which was turned by a foot pedal.

The charkha, or (spinning) wheel was developed in India.

The spinning wheel was introduced to Europe in the 14th Century. The factory system began in the 18th Century, when spinning was done by a class distinctive from weavers. In 1764, an Englishman named James Hargreaves invented the first spinning Jenny – a machine that turned more than one spinning wheel at a time. Other inventions for improving the spinning process followed and the Industrial revolution made mass production possible as power operated machines and then computer controlled machines took over the hand process.

Hargreaves spinning Jenny.

The basic principles of spinning are the same now as in the past, although modern computer controlled spinning machines are specialized and so can adapt to the characteristics of the fibers used – length, cohesiveness, diameter, elasticity and surface contour. These spinning systems are spoken of as conventional spinning system because they are an outgrowth of the traditional methods.

Computer controlled textile spinning machine.


The Cotton System
General
Since the cotton system of spinning yarn is representative of others, it is discussed here in detail. References are made to the woolen system.

The steps in spinning stable fiber into yarn are designed to clean and to make parallel the fibers in order to draw them out into a fine strand and then to twist them to give strength to the finished yarn.

Conventional spinning traditionally has been a series of operations done by individual machines and a great deal of hand labor was involved. In the early 1950s an automated continuous spinning system began to develop in which the operation of each machine and the movement of fibers from machine to machine is controlled automatically. By the 1980s these operations were computer controlled. The table below summarizes seven processes that occur for the cotton system in order to create fibers into yarns.

The Cotton system of operations.
Courtesy reference [1].

We shall deal with each operation separately in order to give a clearer picture of the operation which must be invoked.

Opening
Cotton fibers have been compressed very tightly in a bale and may have been stored in this state for over a year or so. The initial step of opening (or loosening) is necessary to make the fibers ready for carding. Also, machine picked cotton contains a much higher percentage of dirt and trash than does handpicked cotton; consequently, the work of cleaning it has become more complicated. (Part of the cleaning process is done at the gin.) Cotton varies in quality from bale to bale; during various spinning operations the fibers from several bales are blended to give yarns of uniform quality.

Opening is the first operation and it loosens, cleans and blends the fibers through a chute feed system in which bales travel in a straight line across the beaters. The beaters pluck small tufts of fibers. At the same time, dirt and trash are removed by high velocity air.

Bale plucker machine. No textile mill can work efficiently without this machine. All it does is to pluck cotton from bales placed by its side and take it into the machine for opening and cleaning. This is an automatic machine that just plucks cotton like you would pluck a flower.

Carding
Basically carding is done by a machine consisting of two cylinders covered with a heavy card clothing – a heavy fabric embedded with especially bent wires. The fibers are fed between two cylinders, which straighten them and form them into a thin web that is brought together as a soft rope called a card sliver (pronounced sly-ver). In automatic spinning, the carded web is formed into a sliver ribbon, which is combined with the ribbon sliver from other machines in line and then fed into a sliver can, which is automatically filled and delivered to the drawing frames.

Short cotton fibers are processed on the carding machine and yarns made from them are called carded yarns.

Carding machine.

Combing
Combing is the operation that follows carding, when long-staple fibers are to be spun. The fundamental purpose of combing is to separate any short fibers from the long staple so that the combed fibers will be of a much more uniform length and of longer average staple. Combing is quite expensive and adds considerably to the cost of the yarn. Long-staple fibers cost more per dollar than short staple since as much as one-fourth of the fiber is combed out as waste.

Combing machine in cotton mill, Guangdong Province, China.

Fibers emerge from the combing machine as combed sliver and yarns. These combed cotton fibers are called combed yarns. Combed wool sliver is referred to as top and yarns made from them are worsted yarns. The short fibers that are combed out are called noils. The noils are used to make woolen yarns.

Top, combed yarn made from long staple wool fiber – worsted yarn. Bottom, carded yarn made from short staple wool fiber – woolen yarn.
Courtesy of reference [1].

Combing produces yarn of high quality, great uniformity, more strength and finer count. The diagram above shows the parallelism of fibers in a worsted yarn. The chart below gives a comparison of woolen and worsted yarns.

Effect of woolen and worsted yarns in fabrics.
Courtesy reference [1].

Drawing
Drawing blends several slivers together and makes the fiber parallel in structure. This further blends the fibers and contributes to a more uniform yarn. It is done by four sets of rolls, each running successfully faster than the preceding set. The speed is adjusted so that it produces one drawn sliver comparable in size to the individual slivers that were fed into the drawing machine. The drawn sliver comes out much faster than the carded (or combed sliver) is fed in.

Diagram of drawing rolls.
Courtesy reference [1].

Roving
Roving is a term applied to both the process and its product. The aim of the process is to draw out (draft) the drawn sliver to a size suitable for spinning. This drafting is done by a set of rollers similar to those of the drawing machine. Also, it increases the parallelism of the fibers, and when two or more slivers are drawn together (doubling) the uniformity of the yarn will be improved.

Diagram of a roving machine.
Courtesy reference [1].

Roving, the product, is not coiled in a can, as was carded or combed sliver, which has very little strength, but it is given a slight twist and wound on a bobbin. The twist is inserted by a flyer (as shown above). A roving, the product, is a continuous, soft, slightly twisted strand of fibers produced from a sliver. A roving is comparable in size to a thin pencil.

Spinning
Spinning is the final operation in the making of a single yarn. Spinning inserts the twist that gives strength to the yarn and winds the finished yarn on a bobbin. The ring spinning machine, a down-twisting machine, draws, twists and winds in one continuous motion. Drafting rolls draw out the roving to its final size. A traveler, which glides freely around a ring, inserts the twist as the spindle rotates a bobbin on which the yarn is wound.

Diagram of a spinning machine.
Courtesy reference [1].

Mule spinning is done on a spinning frame with an intermittent action and it is used in the woolen spinning system. The yarn is drawn out and twisted, then the twisting stops while the twisted portion of the yarn is wound on the bobbin.

A spinning frame is a multiple machine with a large number of individual units.

A modern spinning frame.

Winding
The spun yarn is wound from the bobbin to spools or cones. The spools are placed onto a large creel and the yarns are wound from the spools onto a warp beam, ready for weaving (as shown below). This operation is called creeling and is performed at the weaving mill.

Creeling yarns onto beams.


Characteristics of Spun Yarns
The first spun yarns were made from wool, linen and cotton, all of which are staple fibers. Yarns made from man-made fibers give fabrics a cotton-like, wool-like or linen-like appearance. Spun yarns are suited to fabrics for clothing in which absorbency, bulk and warmth are desired. The fiber ends hold the yarn away from close contact with the skin; thus a spun yarn is more comfortable on a hot humid day than a fabric of smooth filament yarns.

Spun yarns are characterized by protruding fiber ends. Carded yarns, made of short fibers, have more protruding fiber ends than combed yarns, which are made of long-staple fibers. Protruding ends contribute to a dull fuzzy appearance, to the shedding of lint, and to the formation of pills on the surface of the fabric. Fuzzy ends can be removed from the yarn or from the fabric by singeing.

The strength of the individual staple fiber is less important a factor in yarn strength than it is in filament yarns. Instead, spun yarn strength is dependent on the cohesive or clinging power of the fibers and on the points of contact resulting from pressure of twist. The greater the number of points of contact the greater the resistance to fiber slippage within the yarn. Fibers with crimp or convolutions make a greater number of points of contact. The friction of one fiber against another gives resistance to lengthwise slippage. A fiber with a rough surface – for example wool scales – creates more friction than smooth fiber.


Reference:
[1] N. Hollen and J. Saddler, Textiles, 3rd Edition, MacMillan Coompany, Toronto (1968).

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