Weft Knitting

Knitting

The method of converting yarn into fabric by intermeshing loops, which are formed with the help of needles, is known as knitting. Knitted fabrics provide comfortable wear to almost any style of garment. Most knits contour to the body's silhouette without restricting movement because of its open structure. This makes knit fabrics ideal for innerwear, body wear and sportswear garments. While many variations of knit fabrics exist such that used for hosiery, there are two basic types of knit fabrics—weft knits and warp knits—and it's the direction in which the yarns making up the fabric are looped that determines which type of knit the fabrics. From these two types of knit fabrics come various subtypes that consumer encounter in fabric stores and read with in garment descriptions.

Weft Knitting

Weft knitting is the simplest method of converting a yarn into fabrics. Weft knitting is a method of forming a fabric in which the loops are made in horizontal way from a single yarn and intermeshing of loops take place in a circular or flat form on a crosswise basis. In this method each weft thread is fed, more or less, at right-angle to direction in which fabric is formed. Each course in a weft knit builds upon the previous knitted course. Most of the weft knitting is of tubular form. It is possible to knit with only one thread or cone of yarn, though production demands have resulted in circular weft knitting machines being manufactured with upto192 threads (feeders).

Types of weft knitting

1. Plain Knit
2. Purl Knit
3. Interlock Knit
4. Rib Knit

Plain Knit

If a weft knitted fabric has one side consisting only of face stitches, and the opposite side consisting of back stitches, then it is described as a plain knitted fabric. It is also frequently referred to as a single jersey fabric (single fabric). Plain knitted fabrics are produced by using one linear array of needles. As such all the stitches are meshed in one direction. These fabrics tend to roll at their edges. They roll from their technical back towards the technical front at the top and lower edges. They also roll from their technical front towards the technical back at their selvedges (the self-finished left and right-hand edges of the fabric). The structure is extensible in both lateral and longitudinal directions, but the lateral extension is approximately twice that of the longitudinal extension.

Characteristics

• Stretch crosswise and lengthwise
• Stretches more in the crosswise
• Tend to run or ladder if stitch breaks
• Fabric less stable and curls when cut
• Special finishes counteract curling and improve stability
• Highest machine productivity

End Uses

• Sheets
• Sweaters
• Terry robes
• T-shirts
• Men's underwear
• Dresses
• Hosiery and pantyhose
• Fully fashion garments

Purl Knit

If on both sides of a relaxed weft knitted fabric only reverse stitches are visible, then this is defined as a purl knitted fabric. Purl fabrics are produced by meshing the stitches in adjacent courses in opposite directions either by using special latch needles with two needle hooks or by transferring the fabric from bed to bed between each knitting action. When the fabric is stretched lengthwise, then the face stitches are visible. The fabric shrinks more in the direction of wales, and once it is released, it relaxes to hide the face stitches between the courses. The interloping of the stitches of adjacent courses in opposite directions results in the courses of a purl knitted structure closing up. The structure, therefore, has a large longitudinal extensibility.

Characteristics

• Slowest of the knitting machines
• Both side similar appearance
• More expensive
• Good stretch in all direction
• Stretches out of shape easily
• Crosswise stretch less than a jersey knit
• Thicker than jersey knits
• Does not curl
• Can be unrove from either end

End Uses

• Infant and children's wear
• Sweaters
• Scarves
• Fancy garment parts

Interlock Knit

Interlock knitted structures could be considered as a combination of two rib knitted structures. The reverse stitches of one rib knitted structure are covered by the face stitches of the second rib knitted structure. On both sides of the fabric, therefore, only face stitches are visible, and it is difficult to detect the reverse stitches even when the fabric is stretched widthwise. The geometry of the yarn path influences the stretch behavior of the knitted fabrics. The change of direction of the meshing of the stitches in adjacent wales results in the wales of a rib knitted fabric closing up giving it better stretch properties widthwise as opposed to other basic knitted structures. The combination of two rib knitted structures in the interlock structure gives very little or no room at all for the wales or courses to close up and therefore the interlock fabrics shows relatively poor stretch properties in both directions.

Characteristics

• Reversible
• It does not curl
• Firmer fabric
• Less extensible as compared to other jersey fabrics
• Heavier and thicker as compare to rib
• It unrove from the course knitted the last
• Costlier fabric
• Better insulator

End Uses

• Outwear fabric
• Dress wear
• Skirt
• Blouses
• T-shirts

Rib Knit

If on both sides of a relaxed weft knitted fabric only face stitches are visible, then it is referred to as a rib knitted fabric. It is produced by meshing the stitches in adjacent wales in opposite directions. This is achieved by knitting with two needle systems which are placed opposite to one another other. As such these fabrics are also known as double jersey or double face fabrics. When the fabric is stretched widthwise, both sides of the fabric show alternately face and reverse stitches in each course. Once the fabric is released, it shrinks in its width, thus hiding the reverse stitches between the face stitches. These fabrics do not curl at their edges. The simplest rib structure is 1 x 1 rib shown on the right (click on a thumbnail to view an interactive 3D image and examine the structure). The longitudinal extensibility of the rib structure equals that of a plain knitted structure. The geometry of the yarn path influences the elastic behavior of the knitted structures. The change of direction of the interloping of the stitches of neighboring wales (cross-over points) results in the wales of a rib knitted structure closing up. This gives rib structures better widthwise stretch properties than other basic knitted structures.

Characteristics

• Also called as double jerseys fabric
• Its reversible fabric
• More elastic than jersey knits
• More thicker than jersey knits
• More stretch crosswise than lengthwise
• Edges do not curl
• Very stable
• Running and laddering still a problem
• More expensive to produce
• Next highest machine productivity

End Uses

• Collars and cuffs
• Necklines
• Bottom edges of sweaters
• Double knits jackets
• Knit hats
• Men's hosiery