Weft Knitting, Produce weft knitted fabric

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Weft Knitting 

There are three fundamental stitches in weft knitting: (1) plain knit stitch, (2) purl stitch, (3) rib stitch. Novelty stitches are variations of these three stitches. The hand method of knitting is weft knitting. On a knitting machine, the individual yarn is fed to one or more needles at a time 

1. Plain-knit Stitch: The plain knit is the basic form of knitting. It can be produced in flat-knit or in tubular (or circular) form. The flat knit is also called jersey stitch because the construction is like that of the turtleneck sweaters originally worn by English sailors from the Isle of Jersey; it is sometimes called balbriggan stitch after the hosiery and underwear fabrics made in Balbriggan, Ireland. Plain flat knits may be shaped or full-fashioned. The knitting is done with a row of latch or beard needles arranged in a linear position on a needle plate or in a circular position on a cylinder. All the needles are evenly spaced side by side and are moved by cams, which act on the needle butts. The spacing of the needles is referred to as the gauge, gage, or cut. As applied to many flat knits and some circular ones, gauge refers to the number of needles in 11/2 inches; for example, a 60-gauge machine would have 40 needles per inch. 

2. Purl Stitch: This construction is also referred to as the link-sand links stitch after the German word “links,” or on the left). It is made on flat-bed and circular machines by needles using hooks on both ends to alternately draw loops to the front of the fabric in one course and to the back in the next course. It is a slower and more costly technique. The fabric looks the same on both sides and resembles the back of the plain knit. Like the plain knit, the purl knit will run up and down if a loop is broken. But a purl knit fabric will not curl at the edges. 

3. Rib Stitch: Rib-knit fabrics have alternating lengthwise rows of plain and purl stitches constructed so that the face and back of the fabric appear alike. This may be produced either on a flat rib machine or a circular rib machine. In the flat rib machine, one set of needles is placed opposite the other set of needles is placed opposite the other set of needles in an inverted V position of 45 degrees to the horizontal; in the circular rib machine, one set of needles is placed vertically in a cylinder and the other set of needles is placed horizontally on a dial. In both machines, one set of needles pulls the loops to the front and the other set pulls the loops to the back of the fabric. Each set of needles alternately draws loops in its own direction, depending upon the width of the rib desired. 

For example, rib stitches can be 1 x 1, 2 x 2, 2 x 1, 3 x 1, and so on. A combination of 1 x 1 and 2 x 2 is called an accordion rib. Rib construction is costlier because of the greater amount of yarn needed and the slower rate of production Rib knits are made on a two-bed machine with one set of needles forming the loops for one wale and the other set of needles forming the alternating wale.Rib knits have greater elasticity in the width than in the length. They are stable and do not curl or stretch out of shape as do the jersey knits. For this reason, they are often used to make cuffs and necklines on weft knitted garments. Rib knits are reversible unless the number of stitches in the alternating wales is uneven, as in a 2 X 3 rib.

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Knit Fabric; Different types and classification of knitted fabric

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Single Jersey Knits Fabric  

Knitting Machines with one needle bed and one set of needles are called jersey machines or single-knit machines. With one set of needles used for knitting and one needle bed, all needles face the same direction; all stitches are pulled to the same side of the knitted fabric. As a result, single jersey fabrics have a smooth face with a vertical grain on the right side of the fabric and a width wise grain on the back side. The knittig loops formed by the jersey machine are formed in one direction only, which gives a different appearance to each side of the fabric. The basic knit fabric produced by this knitting machine is known alternately as a plain, single knit, or jersey. The terms are interchangeable.Jersey stretches slightly more in the crosswise than the lengthwise direction. If one stitch breaks, the fabric may ladder, or run. Jersey fabrics tend to curl at the edges and are less stable than are some other types of knits. This is the result of the pressures exerted during knitting. In addition jersey knits may twist or skew after laundering, as the twisting tensions imposed during the knitting process are relaxed. 

Special finishing techniques are used to overcome these tendencies and maintain fabric stability; the principal ones use starches, gum mixtures, polyvinyl acetate emulsions, and resins. 

A great many items of hosiery, sweaters, and other wearing apparel are made from plain jersey knits. Consumer Brief 16.1 highlights one of the common uses of jersey knit fabrics: Tshirts. Plain knit fabrics can also be made into designs of two or more colors by use of a patterning mechanism that controls the selection and feeding of yarns and types of stitches to create jacquard knits. 

Double Jersey Knit Fabrics 

The term double knit is generally applied by consumers to fabrics that are, technically, double jersey fabrics. Double jersey fabrics are also made on two-bed knitting machines, but the arrangement of the needles is different from that for knitting rib fabrics. The layers of loops alternate from one side to the other, locking the two layers together. Double knit fabrics have the same appearance on both sides of the fabric, that is, exhibiting the appearance of the face or outer side of a single knit on both sides. Twice as much yarn is incorporated into double knit fabrics as into comparable single knits 

Interlock Knit fabric

Interlock knits are produced on a special machine that has alternating long and short needles on both beds. Long and short needles are placed opposite each other. Long needles knit the first feeder yarn; short needles knit the second feeder yarn. The fabric created is an interlocking of two 1 X 1 rib structures. The resulting fabric, like double knit fabrics, is thicker than single knit fabric, and more stable in the width wise direction. Interlock fabrics have been traditionally used for underwear. They are produced more slowly than are other rib knits and are generally made in plain colors or simple patterns because the addition of pattern slows down the manufacture even further 

High Pile Fabrics 

High-pile fabrics, such as imitation furs and plushes, are usually knitted by a jersey machine. While the knitting is taking place, a sliver of staple fiber is fed into the machine. These fibers are caught in the tight knit and are held firmly in place. Although any staple fiber can be used for the pile, the greatest quantity of these fabrics are made with acrylic and modacrylic fibers in the pile. By using staple fibers of varying lengths, adding color through fiber dyeing or printing on the surface of the pile, and by shearing or brushing the pile, an enormous variety of effects can be achieved. The use of knitted pile fabric ranges from excellent imitations of furs, such as leopard, tiger, mink, or mouton, to colorful pile outerwear, coat linings, or pile carpet fabrics.

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Gauge and Quality; Knitting machine element to produce knit fabric

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Gauge and Quality 

The size of the needle and the spacing of the needles on knitting machines determine the number and size of the knit stitches and their closeness those are known as knitting element. Each wale is formed on one needle. The number of needles is equal to the number of Wales. The closeness of the stitches determines whether a knit fabric will be lightweight and open or heavier and more dense. The term gauge is used to describe the closeness of knit stitches. Gauge is the number of needles in a measured space on the knitting machine. Higher-gauge fabrics (those with more stitches) are made with finer needles; lower gauge fabrics are made with coarser or larger needles. 

The term cut is also used to designate the number of needles per inch in the needle bed of a circular weft knitting machine. To describe the stitch density of a single or double knit fabric, the fabric may be designated as an 18-, 20-, 22-, or 24cut fabric. The higher the cut, the closer the stitches; the lower the cut, the coarser the fabric. 

Varying types of knitting machines measure gauge over different distances on the machine. For example, circular knit hosiery measures the number of needles in 1.0 inch, fullfashioned knitting in 1.5 inches, and Raschel knits in 2.0 inches. 

Because of these differences, it is best to keep in mind the generalized principle that the higher the gauge, the closer the stitches. 

The quality of needles used in manufacturing knit goods is related directly to the quality of the fabric produced. Needles of uneven size and quality will produce knit fabrics with unevensized stitches and imperfect surface appearance. 

In warp knits, those knits in which the yarns interlace in the long direction, one or more yarns are allotted to each needle on the machine, and those yarns follow the long direction of the fabric. For weft knits, those in which the yarns interlace crosswise or horizontally, one or more yarns are used for each course, and these yarns move across the fabric. In weft knits, one yarn may have from twenty to several hundred needles associated with it. To summarize, weft knits can be made with one yarn, but warp knits must have a whole set of warp yarns, that is, one or more for each needle. 

Once the basic distinction between warp and weft knits has been made, further subdivisions of knit classifications are usually based on the types of machines used in their production. The majority of knit fabrics are named after the machines on which they are constructed. For this reason, the discussion of knitted fabrics that follows is organized around the types of machines used in manufacturing knit fabrics and the types of knit fabrics made on these machines. 

1. Flat or circular jersey, or single knit, machine: one needle bed and one set of needles. 

2. Flat or circular rib machine: two needle beds and two sets of needles. 

3. Flat or circular purl, or links-links, machine: two needle beds and one set of needles.

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