warpknitting

Warp knitting is a family of knitting processes in which loops are formed by guiding multiple yarns, set lengthwise (warp) across the machine, rather than by looping a single yarn back and forth as in weft knitting. The warp yarns are held on a set of warp beams and fed through guide bars as needles interlock them to form fabric along the length of the fabric. The result is a fabric that is generally more dimensionally stable and can be produced at high speed. In warp knitting, each warp yarn forms its own set of loops, and fabrics are produced by interlacing neighboring yarns along the wales; the course direction is produced by machine action rather than by moving the yarn across a fabric surface.

The three principal warp-knitting families are tricot, raschel and Milanese. Tricot fabrics are fine-gauge, smooth-faced and widely used in lingerie and hosiery. Raschel machines, using latch or compound needles, can produce very open laces, nets and bulky fabrics, including lace patterns, swimsuits, and upholstery; Milanese produces chain-like structures for open fabrics and lace. Other forms include weft-insertion warp knits and jacquard patterns with multiple guide bars.

Warp-knitting machines use multiple guide bars (often arranged in dozens) to feed different yarns. The machine advances the fabric as the needles form interlockings, and the fabric is taken up from the loom onto a roll or stack. Applications span fashion apparel, underwear, outerwear, sportswear, lace fabrics, automotive interiors, geotextiles and medical textiles.

Advantages include high productivity, good dimensional stability, and the ability to produce complex patterns and lace. Limitations can include higher equipment cost, limited stretch in some structures, and specialized finishing requirements.