Report on The Wefts Knitted Fabric.

Introduction:  

The wefts knitted fabrics have become comfortable and are in tune with the times. The present generation is grown-up with the permanent press and they are going to demand wrinkle free, ease-of-care fabrics. The recent success of knits has been greatly due to their easy care properties. The mobility of people, in general, has been increased due to facilities for quick transport. Travelers usually need carefree fabrics. And knitted fabrics do comply with this requirement, as they generally require no ironing and are, therefore, ideal for traveling persons. Also for swimwear and sportswear. Also knitting units require very less labor and hence all problems related with labor organization, wages, benefits to labor etc. are very much reduced in the weft knitting industry. So that people can get all these advantages with the knitted fabrics at comparatively low prices. Therefore it is necessary to study about the properties of weft knitted fabrics produced from different types of structure. Knitted fabrics structures are classified according to the arrangement of loops in their courses and Wales. Four primary structures are Plain, Rib, Purl, and Interlock. Here we will study about the 1´1 Rib, 1´1 Skeleton rib, 2´2 English rib, 2´2 Swiss rib, 6´3 Derby rib fabrics properties produced from 100% Cotton combed yarn (20/2Ne, 32/2Ne). Tested properties are courses/cm, Wales/cm, stitch density, stitch length, GSM, tightness factor, dimensional stability.

Effect of Fabric Structure on Rib Properties

Structure of rib fabric is most important factor for rib fabrics properties. Different structure show different value for wales per cm, course per cm, Stitch length, Stitch density, Tightness factor, GSM, Dimensional stability if the same yarn  and machine setting are used. Fabrics sample were knitted at the V-bed knitted machine (keeping the yarn tension, take down tension value, gauge value constant), 14 Gauge and 40 inch width.

Different rib structure is produced by increasing or decreasing no of active needle in knitting. When Increase of the no. of active needle in knitting the fabric shrinkage and extension percentage is reduced and also affect the other knitted fabrics properties. In this project we find out effect of fabric structure on rib fabric properties we study about the comparison between different structures.

Methodology

For the study of “Effect of fabric structure on Rib fabric properties”, five rib fabric 1×1 Rib,1×1 Skeleton Rib, 2×2 Swiss Rib, 2×2 English Rib, 6×3 Derby Rib were produced. On each sample the following test parameters were measured.

• Wales per 3cm
• Course per 3cm
• Stitch density
• Stitch length
• Tightness factor
• GSM
• Dimensional stability

Limitation:
In this project work we faced the following limitations:

1. In a short time we complete this project work.
2. It will better if we submit more statistical analyzed data.
3. It will better if we collect yarn at the start of the project work.
4. It will better if we produce more sample structure.
5. We work with 10 data for each fabric property. It will better if we work with more data.
6. We could not get more time to revise our data three more times. So it is not impossible that, some mistake in the data table

Literature Review

Introduction:

The contribution of knitwear in textile sector export has shown phenomenal growth during the recent years. The knitted fabrics are very soft, elastic, absorbent, and durable having wonderful adaptability and are available at comparatively low prices. Despite of all these advantages there are certain quality limitations connected with the knitted fabrics.

Fabric structure and property:

In garment length knitting, a direct change of knitting from 2×2 and 1×1 rib brings every third needle into action. At the first course, the limbs of the loops knitted on these formerly empty needles open out, producing apertures between every two wales that spoil the appearance of the structure. This problem is overcome by knitting a tubular cover course of plain on all needles in one bed, then on all needles in the other bed. On each side, the sinker loops draw the wales together and prevent the loops on the newly- introduced needle from forcing the wale apart.

1×1 rib is alternately balanced by alternate wales of face loops on each side; it therefore lies flat without  cut when cut. It  is more expensive fabric to produce than plain and is a heavier structure; the rib machine also requires finer yarn than a similar gauge plain  machine. Like all weft knitted fabrics, it can be unroved from the end knitted last by drawing the free loop heads through to the back of each stitch it can be distinguished from plain by the fact that the loops of certain wales are withdrawn in one direction and and the others in opposite direction, whereas the loops of plain are always withdrawn in the same direction, from the technical face to the technical back

Experimental decision:

1. Wales per cm increase with the increase of no of active needle in knitting.
2. Course per cm increase with an increase in loop length.
3. Wales per cm decrease with an increase in loop length.
4. Loop length increases after wet relaxation process when compared to that of the value set in the machine.
5. Thickness of fabric increase with an in increase in loop length.
6. Shrinkage produced in the direction of wale and course wise extension is occurring.
7. From the study, it is found that the shrinkage and extension percentage increases with the increase of needle drop.

Raw Material

Cotton today is the most used textile fiber in the world.

Its current market share is 56 percent for all fibers used for apparel and home furnishings and sold in the U.S. [1]. Another contribution is attributed to nonwoven textiles and personal care items. It is generally recognized that most consumers prefer cotton personal care items to those containing synthetic fibers. World textile fiber consumption in 1998 was approximately 45 million tons. Of this total, cotton represented approximately 20 million tons. [2]. The earliest evidence of using cotton is from India and the date assigned to this fabric is 3000 B.C. There were also excavations of cotton fabrics of comparable age in Southern America. Cotton cultivation first spread from India to Egypt, China and the South Pacific. Even though cotton fiber had been known already in Southern America, the large-scale cotton cultivation in Northern America began in the 16th century with the arrival of colonists to southern parts of today’s United States. [3] .The largest rise in cotton production is connected with the invention of the saw-tooth cotton gin by Eli Whitney in 1793. [4] With this new technology, it was possible to produce more cotton fiber, which resulted in big changes in the spinning and weaving industry, especially in England

Introduction:

Kinds and types of cotton

Scientific Name of cotton

(i)   Gossypium Herbaceum

(ii)  Gossypium Arboreum

(iii)  Gossypium Hirsutum

(iv)  Gossypium Barbedense

Different kinds and types of cotton are grown in various parts of the world. Variation among cotton fibers occurs because of growth conditions including such factors as soft, climate, fertilizers, and pests. The quality of cotton fiber is based on its color, staple, fineness, and strength. Usually, the longer fibers are finer and stronger. The particular kind of cotton is often identified by the name the country or geographical area where it is produced. Though many species of cotton are grown commercially, they may be conveniently divided into three types.

•   Type 1 fibers have staple lengths (i.e. average fiber length) varying from 25 to 60 mm, including high quality fine cottons such as the Egyptian, Sudanese and Sea Island varieties.
•   Type 2 fibers are coarser species, which form the bulk of the world crop with shorter lengths (about 13-33mm) such as American Upland cotton.
•   Type 3 fibers are of still shorter staple length (about 9-25mm) commonly produced in various Asian countries.

Major cotton producers at the present time are China, the USA, India, Pakistan, Uzbekistan; other countries producing small but not insignificant quantities include Brazil, Turkey, Mexico, Egypt, and Sudan. At present the four largest exporters of cotton in the world are USA, Uzbekistan, Franc-zone Africa and Australia. The major high quality cotton fiber classes are listed below:

1.American Upland cotton fibers: They are fairly white, strong, and dull, and range in staple length from 22-32 mm. The Upland cottons are usually categorized as short staple, medium-staple, and long staple. The short staple are less than 25 mm and are produced in Oklahoma and central and West Texas. The medium-staple cotton is 25-28 mm in length are produced in Southeast, the MississippiValley, and the low valleys of Arizona and California. The long staple cottons are 29 mm or longer and are grown in the high altitude areas of the Southwest. The cotton grown in the San Joaquin valley of California has a staple length from 28-29 mm and is stronger than the other Upland kinds.

2.American Pima cotton fiber: It is fine, strong, lustrous, silky and creamy-brown-white in color. The fiber has the staple length from 35-38 mm. American Pima fiber is used for primarily for sewing thread and also used in high-quality broad cloth and other fabrics where silky smoothness, softness, and luster are desired.

3.Egyptian cotton fibers: They are light brown, fine strong and 32-38 mm in length. They are used in the same application as American Pima.

Cotton grading

American Cotton Grading:

The grading of American upland cotton is based upon three main characteristics: color, trash content or foreign, and preparation. It is important to note that staple length is not one of the three. The color may be referred to as extra white, white, spotted, tinged, and yellow stained, in decreasing order of merit. The variety, weather, sofl, picking,efficiency, and so on, governs, the color. The main eight American cotton grades are given below:

i.      Middling fair

ii.      Strict good middling

iii.      Good middling

iv.      Middling

v.      Strict low middling

vi.      Low middling

vii.      Strict good ordinary

viii.      Good ordinary

Indian Grading:

1. Super Choice
2. Choice
3. Super fine
4. Fine
5. Fully good
6. Good
7. Fully good fair

Egyptian Grading:

1. Extra fine
2. Fine
3. Good
4. Fully good fair
5. Good fair
6. Fair

Characteristics of cotton

Cotton, as a natural cellulose fiber, has a lot of characteristics, such as;

• Comfortable Soft hand
• Good absorbency
• Color retention
• Prints well
• Machine-washable
• Dry-cleanable
• Good strength
• Drapes well
• Easy to handle and sew

Uses of cotton

• Apparel – Wide range of wearing apparel: blouses, shirts, dresses, childrenswear, active wear, separates, swimwear, suits, jackets, skirts, pants, sweaters, hosiery, neckwear.

• Home Fashion – curtains, draperies, bedspreads, comforters, throws, sheets, towels, table cloths, table mats, napkins

 Structure and properties of cotton fibers

 Fiber structure and formation

The botanical name of American Upland cotton is Gossypium Hirsutum and has been developed from cottons of Central America. Upland varieties represent approximately 97% of U.S. production [4].

Fiber structure and formation

The botanical name of American Upland cotton is Gossypium Hirsutum and has been developed from cottons of Central America. Upland varieties represent approximately 97% of U.S. production [4].

Each cotton fiber is composed of concentric layers. The cuticle layer on the fiber itself is separable from the fiber and consists of wax and pectin materials. The primary wall, the most peripheral layer of the fiber, is composed of cellulosic crystalline fibrils. [9] The secondary wall of the fiber consists of three distinct layers. All three layers of the secondary wall include closely packed parallel fibrils with spiral winding of 25-35^o and represent the majority of cellulose within the fiber. The innermost part of cotton fiber- the lumen- is composed of the remains of the cell contents. Before boll opening, the lumen is filled with liquid containing the cell nucleus and protoplasm. The twists and convolutions of the dried fiber are due to the removal of this liquid. The cross section of the fiber is bean-shaped, swelling almost round when moisture absorption takes place.

The overall contents are broken down into the following components.

 Raw cotton components:

Repeat unit of cellulose

The current consensus regarding cellulose crystallinity (X-ray diffraction) is that fibers are essentially 100% crystalline and that very small crystalline units imperfectly packed together cause the observed disorder.

The density method used to determine cellulose crystallinity is based on the density gradient column, where two solvents of different densities are partially mixed. Degree of Crystallinity is, then, determined from the density of the sample, while densities of crystalline and amorphous cellulose forms are known (1.505 and 1.556 respectively). Orientation of untreated cotton fiber is poor because the crystallites are contained in the micro fibrils of the secondary wall, oriented in the steep spiral (25-30^o)to the fiber axis.

The micro- structure of cotton –

Length – 1cm to 6.5cm (.5 to 2 inch).

Diameter – 11μm to 22 μm.

Convolutions – sixty per centimeter

Colour – generally white, may be creamy or brown.

Length width ratio – 6000:1 to 350:1

Light reflection – low luster, dull appearance.

Fibers properties

Physical properties of cotton

Fiber length

Fiber length is described [7] as “the average length of the longer one-half of the fibers (upper half mean length)” This measure is taken by scanning a “beard ” of parallel fibers through a sensing region. The beard is formed from the fibers taken from the sample, clasped in a holding clamp and combed to align the fibers. Typical lengths of Upland cottons might range from 0.79 to 1.36in.

Cottons come from the cotton plant; the longer strand types such as Pima or SeaIsland produce the finest types of cotton fabrics [18].

Length uniformity

Length uniformity or uniformity ratio is determined as ” a ratio between the mean length and the upper half mean length of the fibers and is expressed as a percentage”[7]. Typical comparisons are illustrated below.

Low uniformity index shows that there might be a high content of short fibers, which lowers the quality of the future textile product.

 Fiber strength

Fiber strength is measured in grams per denier. It is determined as the force necessary to break the beard of fibers, clamped in two sets of jaws, (1/8 inch apart) [7]. Typical tensile levels are illustrated. The breaking strength of cotton is about 3.0~4.9 g/denier, and the breaking elongation is about 8~10%. [20]

Micronaire

Micronaire measurements reflect fiber fineness and maturity. A constant mass (2.34 grams) of cotton fibers is compressed into a space of known volume and air permeability measurements of this compressed sample are taken. These, when converted to appropriate number, denote Micronaire values.

Color

The color of cotton samples is determined from two parameters: degree of reflectance (Rd) and yellowness (+b). Degree of reflectance shows the brightness of the sample and yellowness depicts the degree of cotton pigmentation. A defined area located in a Nickerson-Hunter cotton colorimeter diagram represents each color code. The color of the fibers is affected by climatic conditions, impact of insects and fungi, type of soil, storage conditions etc. There is five recognized groups of color: white, gray, spotted, tinged, and yellow stained. As the color of cotton deteriorates, the process ability of the fibers decreases.

Trash

A trash measurement describes the amount of non-lint materials (such as parts of cotton plant) in the fiber. Trash content is assessed from scanning the cotton sample surface with a video camera and calculating the percentage of the surface area occupied by trash particles. The values of trash content should be within the range from 0 to 1.6%. Trash content is highly correlated to leaf grade of the sample.

Leaf grade

Leaf grade is provided visually as the amount of cotton plant particles within the sample. There are seven leaf grades (#1-#7) and one below grade (#8).

Preparation

Preparation is the classer’s interpretation of fiber process ability in terms of degree of roughness or smoothness of ginned cotton.

Extraneous matter

Extraneous matter is all the material in the sample other than fiber and leaf. The classer either as “light” or “heavy” determines the degree of extraneous matter. NEPS

A nep is a small tangled fiber knot often caused by processing. Neps can be measured by the AFIS nep tester and reported as the total number of neps per 0.5 grams of the fiber and average size in millimeters. Nep formation reflects the mechanical processing stage, especially from the point of view of the quality and condition of the machinery used.

Chemical properties of cotton

Effect of –

1. Acid: Weaken and destroyed hydrolise the glucoside oxygen atom, concentrate Nitric acid, for short time, causes some shrinkage and increase strength and dye-ability.
2. Alkali: normally resistance, when boiled in presence of O₂ , oxycellulose form, treating with 20 percent NaOH increase strength and dye ability, process is called Mercerization. Liquid ammonia etc.
3. Bleach-All kinds, NaOCl and Na Per borate are common H2O2 is least harmful.
4. Organic Solvent – resistance. So dry wash is possible.
5. Heat – conductive ironing temp – 150⁰ c, Decompose 2400⁰ c, Ignition temp – 390⁰ c.
6. Sun light- Affected by infrared cause deteriorates colour becomes yellow.
7. Dye-ability – Azoic, Direct, Reactive, sulphur and Vat dye.
8. Attack by moth – No
9. Attack by mildew – Untreated not easily but starches and gums increase activity.

Critical temperatures

• Favorable travel temperature range – below 25 °C (77 °F)
• Optimum travel temperature: 21 °C (70 °F)
• Glow temperature: 205 °C (401 °F)
• Fire point: 210 °C (410 °F)
• Autoignition temperature: 407 °C (765 °F)
• Autoignition temperature: (for oily cotton): 120 °C (248°F)

Cotton dries out, becomes hard and brittle and loses all elasticity at temperatures above 25°C (77°F). Extended exposure to light causes similar problems. A temperature range of 25 °C (77 °F) to 35 °C (95°F) is the optimal range for mold development. At temperatures below 0°C (32 °F), rotting of wet cotton stops. Damaged cotton is sometimes stored at these temperatures to prevent further deterioration.

Fiber processing

About 30% of world cotton machines harvest production. Australia, Israel and USA are the only countries where all cottons are picked by machines. Fifteen percent of world cotton production is ginned on roller gins and almost all rest of cotton is saw ginned in most countries [14].Cotton fibers in nonwovens are generally used in their bleached form. A lot of research and development has taken place for the efficient production of bleached fibers. The Kier bleaching process produces most of the bleached cotton fibers. Since cotton of lesser grades is useful for nonwovens, a conventional cleaning system does not suffice. This might include a coarse wire carding, called Cotton Master Cleaners, for cleaning the cotton.

Spinning and its principle

Most of the fibers produced for textile materials are processed into yarns. The principle of the conventional yarn manufacturing method is to introduce a twist into yarn-by-yarn revolution. One revolution gives just one turn of twist. This process is called spinning.

Knitted fabric properties

 1. Wales /cm:

Wales is the column of loops along the length of the fabric. Wales determine the width of the fabric and are measured as wales per centimeter. The no. of wales per centimeter is called wales/cm. It is measured along the course direction by using counting glass and needle.

• When loop transfer occurs it is possible to transfer a wale A to another B and to recommence knitting with the second needle in which case more than one needle will have produced intermeshed loops in the same wale.
• In warp knitting a wale can be produced from the same yarn if the same guide laps the same needle at successive knitting cycles.
• Wales are connected together across the width of the fabric by sinker loop (weft knitting)or under laps(warp knitting).
• Wales show most clearly on the technical face and technical back of single needle bed fabric.
• For single jersey fabric Wales show on face side as V shape and from back side as half circle

Course/cm:

A course is a predominantly horizontal raw of needle loops produced by adjacent needle during the same knitting cycles. Course is a row of loops across the width of fabric. A course determines the length of fabric and is measured as course per centimeter      .

The number of course per centimeter is called course/cm. it is measured along the wale direction by using counting glass and needle.

2.Stitch density:

The term stitch density is frequently used in knitting instead of a linear measurement of courses or wales. It is the total number of needle loops in a square measurement such as a square inch or square centimeter. It is obtained by multiplying the number of courses and wales per centimeter together. Stitch density tends to be more accurate measurement because tension acting in one direction in the fabric, for example, procedure a low reading for the course a high reading for the wales, which then multiplied together cancel the effect out. Usually pattern rows and course are, for convenience, considered to be synonymous when counting course per unit of linear measurement.

Stitch density = wales per cm(wpcm) ×course per cm(cpcm)

3.Stitch length.

The length of yarn knitted in to one stitch in a weft knitted fabric. Stitch length is theoretically a single length of yarn which includes are needle loop and half the sinker loop on either side of it. Generally the larger the stitch length the more extensible and lighter the fabric and poorer the cover, capacity and busting strength.

Stitch length = one needle loop + two half a sinker loop

Stitch length can be determined by a HATRA (Hosiery and Allied Trade Research Association England) courses length tester.

The HATRA courses length tester is simple apparatus consisting of a rectangular board on which scales are marked in inches and cm along the longitudinal axis. A small clamping weight of about 10 gm is provided to remove the crimp from the yarn. To measure the stitch length marking is made at a distance of 50 wales and each courses unraveled carefully from the fabric and measured. About 20 to 30 courses can be measured this fashion to arrive at the average stitch length of 50 loops. This average length is then by 50 to get the divided stitch length.

4.Tightness factor:

Munden first suggested the use of a factor to indicate the relative tightness or looseness of plain weft knitted structure, to be used in a similar manner to that of the cover factor in the weaving industry. Originally termed the cover factor but now referred to as the tightness factor (TF), he defined if as the ratio of the area covered by the yarn in one loop to the occupied by that loop.                                                          The total area covered by yarn is: s×l×d

For single jersey fabrics: K.S values lie between 1.29 to 1.64, mean K=1.47. For most weft knitted structures (including S/J, D/J and wide range of yarns): 1≤ K≤ 2, mean K=1.5

The tightness factor is very useful in setting up knitting machines. At mean tightness factor, the stain in yarn, machine and fabric is constant for a wide range of conditions.

5.GSM:

Weight per unit area can be measured by a portable balance by cutting the fabric in 10″×10″ with the template or by calculation with the formula:

GSM =(Course/cm × Wales/cm× 100 × 100 × l × tex)/1000 × 1000

l = stitch length in millimeter.

The result is expressed in gm/sq.meter, popularly known as GSM.

GSM or weight per unit area of fabric is an important property that is again related to a host of their properties. The weight is determined by two factors that interact the loop size and the yarn size. The effect of loop size is simple express. If the sizes of the yarn remain constant, then increase the loop size produce a decrease of weight per unit area.

6.Dimensional Stability:

The ability of a fabric to retain its dimensions when exposed to use and or an ageing process to water, washing, steaming, drying or other process is called dimensional stability.

In other word, changes in length and or width of a fabric when subjected to specified conditions. It may be extension and shrinkage or relaxation, both length and width direction.

Relaxation:

Knitted fabrics tend to change dimension in width and length after being taken off the machine even without yarn shrinkage indicating a change of loop shape rather than of loop length. During knitting the loop structure is subjected to a tension of approximately 15-25 grams per needle from source as the take down mechanism and in the case of fabric machines, the width stretcher board. Unless the structure is allowed to relax from its strain and distorted state at sometime during manufacturing the more favorable conditions for fabric relaxation provided during washing and wearing will result in a change of dimensions leading to customer dissatisfaction.

Relaxation test can be carried out on fabric as a routine procedure or as spot check on suspect deliveries. There are British Standard procedures for relaxation testing and some of the large retail/whole sales purchasers have established tests of their own. Most test procedures involves by measurement under water and or spinning and tumble drying.

Extension:

Extensibility is a peculiar characteristic of knitted fabric. However, the amount of extensibility expected of a fabric depends on the end use. For example, extensibility of a double knitted fabric needs to be low for many of the uses to which the fabrics are put to, sometimes garments makers also stipulate requirements for fabric extensibility. Usually an extension tester is used two jaws in the machine. A uniform weight is applied to the fabric and the percentage extension is measured by using the formula.

Rib Fabric Structure

1.0Introduction

The first rib frame was invented by Jedediah Strutt  of Derby in 1755, who used a second set of needles to pick up and knit the sinker loops of the first set. It is now normally knitted with two sets of latch needles (Fig – 1, and Fig – 2); Rib has a vertical cord appearance because the face loops show a reverse loop intermeshing on the other side. 1×1 rib has the appearance of the technical face of plain on both sides until stretched to reverse loop wales in between. A rib fabric is defined as a fabric in which all the loops in any individual wale are either knit or purl, it cannot have both in the same wale. The fabric is the same on both sides, therefore it is a balanced fabric which is stable. Rib fabric lies flat without edge curl. The main characteristic of rib fabric is it’s horizontal extensibility.
The rib structure causes the fabric to concertina and pull in, with the result that stitch for stitch a rib fabric has a narrower width than a plain fabric, but can extend to the same width as the plain fabric. Rib structures are good for welts and close fitting garments. They can be composed of any combination of knit or purl wales1x1, 2×2, 2×3 and so on.

2.0Rib structure

2.1   1×1 Rib

The simplest rib fabrics is. It is normally knitted with two sets of latch needles (Diagram-

4). Rib has a vertical cord appearance because the face loop Wales tend to move over and in front of

the reverse loop intermeshing on the other side, 1×1 rib has the appearance of the technical face of plain fabric on both sides until stretched to revel

the reverse loop Wales in between.1×1 rib production of by two sets of needles being alternately set or gated between each other. Relaxed 1×1 Rib is theoretically twice the thickness and half erable stretch. In practice, 1×1

rib normally relaxes by approximately 30 percent compared with its knitting width.1×1 rib is balanced by alternately wales of face loops on each side; it therefore lies flat  without curl when cut. It is a more ex -pensive fabric to produce than plain and is a heavier structure.1×1 rib shown in diagram-1;

2.2    1×1 Skeleton rib

It is possible to produce Skeleton 1×1 rib on V-bed knitting machine by taking every third needle from both bed out of action. Skeleton 1×1 rib shown on Diagram-2.

2.3    2×2 Swiss rib 

2×2 Swiss rib (Diagram-3), this is produced on a rib machine by taking one needle out of action opposite the two needles knitting. Swiss rib is something confusingly termed 2/3 rib   because 2 out of 3 needles in each bed are knitting. It is not possible to commence knitting on empty needles with the normal 2×2 arrangement because the two needles in each bed will not form individual loops – they will make one loops across the two hocks.

2.4  2×2 English rib

2×2 English rib is shown on Diagram-4. English rib is produced on a purl machine or rib machine with two empty tricks opposite to the two needles knitting; this type of rib is less elastic it is possible to produce on V-bed knitting machine.

2.5    6×3 Derby Rib

It is possible to produce 6×3 Derby Rib on V-bed knitting machine. It is produced by six needle in action and two needle out of action in front bed , alternately five needle out of action and three needle in active in bed.

3.0Feature and properties of Rib Fabric

• It is a reversible structure, i.e. face and back side has same appearance in 1×1, 2×2, 3×3 ribs etc. the appearance shows vertical cords and thin ridges, in between.
• 1×1, 2×2, 3×3 ribs etc. are balanced structures because of alternate number of face and reverse Wales in each side.
• It is heavier and thicker structure than the plain knit structure with similar gauge used for plain-knit and rib structure.
• It requires a knitting machine with cylinder and dial and two sets of needle-cylinder needles and dial needles.
• Rib structure cannot be unroved from the course knitted first because sinker loops are securely anchored by the cross-meshing between face and reverse loop Wales. It can be unroved from the last course knitted.
• As mentioned earlier, it has the maximum extensibility in width way and hence rib trimmings are most suitable for neck bands, collars, arm bands, sleeve cuff bands in sweater knitting and for tops of socks, as they fit tighter to the body than the plain knit give a smart appearance.
• Rib fabrics are extensively used in the production of outerwear garments in western world.
• The fabric does not curl at the edges due to its balanced nature. This is property of rib structure is particularly useful in cutting and sewing operations.
• The structure is more opaque than a jersey and hence this structure is used for swimwear.

4.0 Uses of Rib fabric

Rib is particularly suitable for the extremities of articles such as tops of sock, cuffs, sleeves, rib borders of garments and stocking and strapping for cardigans. It is knitted at the tops at the tops of plain knit socks and gloves.

Machine description

1.0Introduction

V – Bed knitting machine is the most versatile weft knitting machines. V- bed knitting machine has two stationary needle beds arranged in an vertical V forma -tion. Latch needles and others slide in the tricks during the knitting action. Their butts project and are controlled as they pass through the tracks formed by the angu

-lar cams of a bi-directional cam system. It is attached to the underside of a carriage that, with its selected yarn carriers, traverses in a reciprocating manner ac

-cross the machine width. There is a separate cam system for each bed, the two sy

-stem are linked together by a bow,or bridge, that passes across from one needle bed to other. The cam systems for each needle bed are symmetrically arranged so that knitting, and in some cases loop transfer, may be achieved in either direction of carriage traverse.

2.0Machine Specification

1)      Type: Flate knit

2)      Company Name: Exse Company Ltd.

3)      Origin:  Made in India

4)      Machine width: 40 inch

5)      Machine gauge: 14

3.0The yarn carriers arrangemen

The yarn carriers are arranged to slide

On both sides of double prismatic guiding bars and there are usually six or seven carriers operate on the same track of the same bar, it is essential to arrange the sequence so that if the two carriers are deposited on the same side, the one nearest to the cam-carriage will be the one first required to traverse back in the opposite direction.

There are two methods of entraining carriers with cam systems on double system machines; uncrossed and crossed arrangement, the same yarn carriers operate with the same cam systems in both directions of traverse. This simplifies the control and is essential when two carriers are on the same track, but it causes problems with vertical yarn floats at the selvedges because the yarn with the leading cam system will finish the first course but will not knit the return traverse.

With the crossed arrangement, one yarn carrier will always be entrained with the leading cam system and the other with the trailing cam system, so that if the carriers have different colored yarns, each will knit alternate courses.