3D knitting is a revolutionary method in textile manufacturing where a three-dimensional shape is created directly on the knitting machine — without the need for cutting or sewing. 3D structures can be knitted, woven and braided to create products that are complete without seams. They are highly successful in commercial knitwear and used in engineering, furnishings and the fashion industry e.g. hats, jumpers, helmets, wheel rims and sofa covers.
3D Knitted Structures
The development and use of 3D shaped knitting technologies are growing in the technical textile field. Over the past few decades, various 3D knitted textiles have been created with the development of high-tech knitting machines. Both weft and warp knitting are used for developing 3D textiles. The most commonly used knitted 3D structures include tubular structures, net-shape structures, spacer structures and DOSs. These structures can be realized with different methods by using 3D knitting technologies.
3D knitted fabrics can be formed into complex shapes with high extensibility due to their draping properties and they can also have high impact properties. They are divided into three groups:
1. Multiaxial – multiple layers of yarns that are vertical, horizontal and diagonal in both directions are held together by the structure of warp knitting, mainly using glass or carbon fibers. This method is often used to reinforce composite materials.
2. Spatial – produced on flat bed or circular CAD/CAM systems, which create fabrics of a complex shape similar to the final product. The courses are knitted on a specific number of working needles that increase and decrease to provide the shape of the product. That shape is usually defined as a 3D body, and it consists of various shapes such as tubes, spheres, cones, pyramids and polyhedrons. Using this method carries certain limitations such as the loss of strength in areas, but that problem can be rectified via the insertion of warp and weft yarns.
3. Sandwich and Spacer Fabrics – these are two separate fabrics that are connected by yarns or knitted layers; the thickness of the fabric is determined by the connecting layer. Spacer fabrics are produced on warp knit machines whereas sandwich fabrics are made on weft knit machines. The connecting layers can be single or double; a single layer is produced on one bed (jersey) or two beds (rib), and it has a perpendicular or slightly angled connecting yarn to separate the fabrics. This trait creates a straight line or V view. In the case of double connecting layers, they are knitted separately on the beds and these fabrics can be formed into various shapes using interior and exterior moulds. The exterior mould creates the desired shape of the composite and the interior mould uses polyurethane foam to create the internal shape required. These moulds are then set with resins to help them maintain the shape permanently.
Techniques of 3D Knitting Technology
Knitting technology has been utilized for centuries to manufacture fabrics in apparel areas. The unique properties of knitted constructions make them able to be engineered to meet exacting requirements of various applications. In addition, the potential for the production of shaped fabrics enables knitting technology to be increasingly used in nonapparel areas. The push towards 3D-shaped knitting for technical textiles has driven manufacturers to develop and apply new advanced technologies in building knitting machines. Today, modern technology has enabled knitting machines to manufacture most previously hand-knitted structures and knitted structures that are too fine, intricate or complex to be knitted by hand. Circular and flat weft knitting as well as warp knitting has been developed to manufacture 3D knitted textiles.
a) Circular weft knitting:
There are two types of circular weft knitting machines: single jersey and double jersey. A single-jersey circular machine has a cylinder with a set of needles arranged vertically in a circular form. In addition to a cylinder, a double-jersey circular machine has a dial with another set of needles, which are arranged horizontally in a circular form. This special arrangement enables circular machines to produce tubular fabrics conveniently. In apparel areas, tubular fabrics are required to be slit into a planar form for subsequent processing. Circular knitting machines with small-diameter cylinders have been employed to manufacture small-diameter tubular structures for medical applications. Double-jersey circular machines also can be used to produce another type of 3D structure: spacer fabrics.
Fig: 3D spacer fabric
b) Flat weft knitting:
Computerised flat weft knitting is the most versatile technology in 3D knitting. The key elements that are essential to the development of 3D knitted textiles include the needle, needle bed, racking mechanism, carriage and cams, yarn carriers, take-down system, yarn threading mechanism, sinkers and stitch presser. By using computerized flat knitting machines, almost all 3D knitted structures can be realized, including tubular structures, net-shape structures, spacer structures and directionally oriented structures (DOSs). Key features of computerized flat knitting include the use of electronics for individual needle selection, loop transfer, stitch variations, multiple yarn carriers, holding down sinkers on the needle beds, stitch presser and motor drive take-down rollers. These capabilities provide opportunities for knitting single face or double face, loop transfer, varying the number of loops in width or depth, knitting from a selection of yarns on a selection of needles and shaped knitting.
c) Warp knitting:
A simultaneous yarn-feeding and loop-forming action is occurring at every needle in the needle bar during the same knitting cycle in warp knitting. This feature enables warp knitting machines to produce warp-knitted fabrics of low cost, high productivity and wide structure variation. Double-needle bar Raschel machines have been used to produce tubular fabrics and spacer fabrics, whereas multiaxial Raschel machines have been used to produce DOSs.
Applications of 3D Knitting in Modern Textiles
3D knitting sometimes called seamless knitting—has rapidly transformed the textile industry, bringing precision, efficiency, and exciting new capabilities to both fashion and technical textiles.
3D knitting creates seamless, custom textiles with minimal waste. It is widely used in fashion, furniture, medical garments, smart textiles, technical fabrics, sports textiles and automotive industries. 3D knitting increases comfort, functionality, and sustainability while enabling new, complex designs that traditional methods can’t achieve. Its applications continue to grow with advancements in textile technology.
Fig: Seat cover
3d-Knit Upholstery
Office seats and sofa covers are produced on V bed, weft knit machines. Loops transfer across the V to produce the required shapes through specific needle selections. They are excellent for Just-in-Time and Quick Response manufacturing because no construction processes are required. Often, upholstery is stapled to the resistant product. The benefits of this process include:
Quick to market – no fabric lengths are required, no cutting or sewing of pieces making it a speedy process; a seat cover can be created within twenty minutes.
No waste materials because the fabrics are shaped for specific end products.
Easier to put covers on products because they are already shaped.
The jacquard design can continue throughout the product without being cut off by seams.
Easy to produce bespoke products.
3D Garments (Total-Garment Technology)
This relates to the making of complete garments with no seams e.g. hats, gloves and jumpers. It uses technological advances in digital stitch control and four-bed knitting machines with compound needles.
Digital Stitch Control System – the yarn feed and tension is automatic for a consistent loop length, and the yarn use is monitored during each course. A tolerance of +/– 1% is established.
Four-Bed Machine Technologies – they provide tubular knitting in rib or stocking stitches. (Knitting with four-needle beds is similar to the hand produced by four-needle, tubular knits). The bodice of a jumper is knitted from the waist to the underarm; the two sleeves from the cuffs to the underarm position, where they are then connected to the bodice. The knit continues to the shoulder, where the neck is shaped. This could make the product reversible.
The use of compound needles allows the stitches to be very close.
Benefits:
Less labor intensive than cut sewing.
Extra comfort and better fit.
Better draping (seams tend to add stiffness) and a softer feel.
Conclusion
3D knitting is changing how we think about making textiles. With its smart techniques, unique fabric structures, and wide range of uses, it’s helping the industry move toward faster, cleaner, and more efficient production. As 3D knitting technology continues to evolve with advanced machinery, software, and material integration, it holds great potential to transform textile manufacturing into a more sustainable, efficient, and innovative industry.
References
[1] Ashford, B. (2016). Fibres to fabrics.
[2] Chen, X. (2015). Advances in 3D textiles. Elsevier.
[3] Gong, R. H. (2011). Specialist yarn and fabric structures: Developments and Applications. Woodhead Publishing.
[4] Au, K. F. (2011). Advances in knitting technology. Elsevier.
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
