Types
Weft Knitting Machines
Weft knitting machines produce fabric by forming successive courses of loops horizontally across the width, with each course typically created from a single continuous yarn fed into the needles.[37] This contrasts with warp knitting, where multiple yarns form loops vertically along the length.[38] The process relies on mechanical needle actions—such as latch, bearded, or compound needles—guided by cams to hook, draw, and cast off yarn loops, enabling high-speed production of extensible fabrics like jerseys, ribs, and interlocks.[39]
These machines originated with William Lee's invention of the stocking frame in 1589, a flat-bed weft knitter that mechanized loop formation for hosiery using bearded needles and a warp-like yarn arrangement but weft-style looping.[4] Circular weft knitting emerged later, with Marc Brunel patenting the first tubular machine in 1816, allowing seamless tube production by rotating a needle cylinder under fixed yarn feeders.[5] Modern developments include electronic controls for pattern variation, with machines achieving speeds up to 3,500 courses per minute in high-production models.[40]
Weft knitting machines classify primarily into circular and flat-bed types, differing in needle arrangement and output shape. Circular machines feature needles mounted radially on a rotating cylinder (and optionally a dial for double-knit), forming tubular or open-width fabrics via continuous revolution, ideal for hosiery, underwear, and sportswear due to seamlessness and efficiency.[1] Flat-bed machines use straight needle beds with a traversing carriage that moves cams across to knit flat panels, suited for shaped garments like sweaters where patterning and seaming are needed, though slower than circular counterparts.[1] Subtypes include single jersey for basic smooth fabrics, rib for elastic edges, and interlock for denser double-faced knits, each requiring specific cam systems and feeders.[41]
Operation involves yarn tension control, precise feeder spacing (typically 1-4 inches apart), and synchronization to prevent defects like dropped stitches, with production rates influenced by gauge (needles per inch, from 12 to 32) and yarn count.[37] Optimal rotational speeds, such as 40 revolutions per minute for certain setups, balance output with yarn integrity, yielding fabrics from 50 to 500 g/m².[42] [43] Advances in compound needles and automation have enhanced versatility, enabling complex jacquards while maintaining the core weft principle of lateral loop intermeshing.[40]
Warp Knitting Machines
Warp knitting machines fabricate textiles by supplying multiple yarns parallel to the fabric's length, with each yarn forming a series of interconnected loops along vertical wales, secured by adjacent yarns' lateral underlaps. This contrasts with weft knitting, where a single yarn traverses horizontally to interloop across courses, as warp knitting demands precise coordination of numerous warp beams to achieve inherent stability and resistance to laddering.[37][34] The resulting structures exhibit superior dimensional stability, retaining shape under tension or laundering due to the longitudinal yarn orientation and interlocking mechanism.[38]
Core components include a knitting element with needles in a fixed bed, multiple guide bars for yarn lapping, warp let-off systems for controlled feeding, and take-up mechanisms for fabric winding. During operation, guide bars shog (shift laterally) and swing to wrap yarn around needle shanks, while needles rise to form new loops over the previous course's sinker loops; bearded, compound, or latch needles facilitate loop closure, with sinkers supporting underlaps.[44][45] Machine gauges, typically 28 to E50 needles per inch, determine fabric fineness, with production speeds varying by type but enabling outputs up to 600 courses per minute in high-performance models.[46]
Tricot machines, employing compound or bearded needles, specialize in high-speed production of smooth, run-resistant fabrics from continuous-filament yarns, operating at over 2000 rpm to yield tricot stitches for applications like linings, underwear, and sportswear.[47][48] Raschel machines, using latch needles and coarser gauges (E0 to E18), provide extensive patterning via up to 12 or more guide bars, suited for openwork structures such as lace trims, nets, and technical textiles including geotextiles and medical meshes.[49][50] Both types support variable beam counts, with raschel favoring versatility in heavy denier yarns for products like cargo nets and protective fabrics.[51]
The technology originated in 1775 with Josiah Crane's English patent for a warp-equipped frame, adapting guides to produce chain-like stitches mechanically.[52][53] By 1805, Joseph Jacquard's selectable shedding advanced pattern control, paving the way for industrialized variants that expanded into diverse sectors by the mid-19th century.[53] Modern iterations incorporate electronic patterning and carbon-fiber elements for precision, though core principles remain grounded in warp-parallel looping for enhanced tensile properties over weft alternatives.[54]
Specialized Modern Variants
Specialized modern knitting machines target niche applications, producing items like socks, gloves, and medical textiles with tailored mechanisms for precision, seamlessness, and material compatibility. These variants often integrate computer controls for patterning, shaping, and quality consistency, enabling high-volume output beyond general fabric production.[55][56]
Sock knitting machines exemplify this specialization, utilizing circular weft techniques to form seamless tubes that are shaped into finished products via automated toe and heel closing. Modern models, such as those employing sinker systems, operate at gauges of 10 to 13 needles per inch, supporting terry, jacquard, or 3D patterns for athletic or therapeutic socks.[55] Computerized variants achieve speeds exceeding 300 revolutions per minute, reducing labor while maintaining uniformity in thickness and elasticity critical for fit.[57]
Glove knitting machines adapt similar circular or flat-bed systems for finger-specific forming, often with individual needle selection for contoured palms and reinforced areas. These produce seamless gloves for industrial, medical, or consumer use, incorporating features like linked toes for dexterity and antimicrobial yarn integration. High-speed models handle multiple yarn feeds, yielding up to 1,000 pairs per shift in automated setups.[58][55]
For medical textiles, custom knitting machines fabricate compression garments, stents, and wound dressings using biocompatible yarns and precise tension control to meet regulatory standards for elasticity and durability. Manufacturers like Lamb Knitting Machine Corporation develop equipment for applications including vascular stents via fine-gauge warp or weft structures and ear-loop cords for masks, emphasizing sterility and customization.[56] These systems prioritize hypoallergenic outputs, with capabilities for graduated compression profiles aiding venous conditions.[56]