Weft and warp knitting

There are two major varieties of knitting: weft knitting and warp knitting. In the more common weft knitting, the wales are perpendicular to the course of the yarn. In warp knitting, the wales and courses run roughly parallel. In weft knitting, the entire fabric may be produced from a single yarn, by adding stitches to each wale in turn, moving across the fabric as in a raster scan. By contrast, in warp knitting, one yarn is required for every wale. Since a typical piece of knitted fabric may have hundreds of wales, warp knitting is typically done by machine, whereas weft knitting is done by both hand and machine. Warp-knitted fabrics such as tricot and milanese are resistant to runs, and are commonly used in lingerie. Weft-knit fabrics may also be knit with multiple yarns, usually to produce interesting color patterns. The two most common approaches are intarsia and stranded colorwork. In intarsia, the yarns are used in well-segregated regions, e.g., a red apple on a field of green; in that case, the yarns are kept on separate spools and only one is knitted at any time. In the more complex stranded approach, two or more yarns alternate repeatedly within one row and all the yarns must be carried along the row, as seen in Fair Isle sweaters. Double knitting can produce two separate knitted fabrics simultaneously, e.g., two socks; however, the two fabrics are usually integrated into one, giving it great warmth and excellent drape. Warp knitting comprises several types of knitted fabrics, including tricot, raschel knits, milanese knits and stitch-bonding. All warp-knit fabrics are resistant to runs and relatively easy to sew. Raschel lace - the most common type of lace - is a warp knit fabric but using many more guide-bars (12+) than the usual machines which mostly have three or four bars. Tricot is very common in lingerie. The right side of the fabric has fine lengthwise ribs while the reverse has crosswise ribs. The properties of these fabrics include having a soft and 'drapey' texture with some lengthwise stretch and almost no crosswise stretch. Milanese is stronger, more stable, smoother and more expensive than tricot and, hence, is used in better lingerie. These knit fabrics are made from tw sets of yarn knitted diagonally, which results in the face fabric having a fine vertical rib and the reverse having a diagonal structure, and results in these fabrics being lightweight, smooth, and run-resistant. Milanese is now virtually obsolete. Raschel knits do not stretch significantly and are often bulky; consequently, they are often used as an unlined material for coats, jackets, straight skirts and dresses. These fabrics can be made out of conventional or novelty yarns which allows for interesting textures and designs to be created. The qualities of these fabrics range from "dense and compact to open and lofty [and] can be either stable or stretchy, and single-faced or reversible. The largest outlet for the Raschel Warp Knitting Machine is for lace fabric and trimmings. Stitch-Bonding is a special form of warp knitting and is commonly used for the production of composite materials and technical textiles. As a method of production, stitch-bonding is efficient, and is one of the most modern ways to create reinforced textiles and composite materials for industrial use. The advantages of the stitch-bonding process includes its high productivity rate and the scope it offers for functional design of textiles, such as fiber-reinforced plastics. Stitch-bonding involves layers of threads and fabric being joined together with a knitting thread, which creates a layered structure called a multi-ply. This is created through a warp-knitting thread system, which is fixed on the reverse side of the fabric with a sinker loop, and a weft thread layer. A needle with the warp thread passes through the material, which requires the warp and knitting threads to be moving both parallel and perpendicular to the vertical/warp direction of the stitch-bonding machine. Stitch-bonded fabrics are currently being used in such fields as wind energy generation and aviation. Research is currently being conducted into the usage and benefits of stitch-bonded fabrics as a way to reinforce concrete. Fabrics produced with this process offer the potential of using “sensitive fiber materials such as glass and carbon with only little damage, non-crimp fiber orientation and variable distance between threads”.