Knitted technology and textile machinery play a pivotal role in modern fabric production, encompassing a diverse range of methods and specialized equipment. From basic loop formation to advanced seamless garments and innovative spacer fabrics, understanding these technologies is crucial for students and professionals in textile engineering. This overview will summarize the fundamental concepts, machinery, and key advancements in knitted textile production.
Unveiling Knitted Technology and Textile Machinery
Knitting is a fabric-forming process where subsequent loops are created from one thread and placed in either the same course (weft knitting) or subsequent courses (warp knitting). This fundamental difference dictates the machinery used and the properties of the resulting fabric. The course refers to horizontal rows of loops, while the wale refers to vertical columns.
Weft Knitted Technology: Principles and Products
Weft knitting involves forming loops horizontally across the fabric. The subsequent loops from one thread are placed in the same course. Key machinery includes:
- Flat knitting machines (V-bed type): These machines can have one needle bed for single-faced structures or two V-beds for double-faced fabrics like rib and purl. They also utilize double hooked needles for purl structures. Latch needles and SlideNeedles are commonly used.
- Circular machines: These vary in diameter (large, body, small) and needle bed arrangements. One bed (cylinder) produces single-faced structures, while cylinder and dial setups create double-faced fabrics (rib, interlock). Two cylinders with double hooked needles are used for purl fabrics.
Weft knitted technology produces a wide range of products, including various garments and fashion items, often with intricate patterns and textures.
Warp Knitted Technology: Principles and Products
In warp knitting, subsequent loops from one thread are placed in subsequent courses, creating a fabric from multiple yarns simultaneously. Key warp knitting machines include:
- Raschel machines: Available in single and double needle bar configurations.
- Tricot machines: Utilize compound, bearded, single, and double needle bars.
- Crochet machines: Employ carabine and latch needles.
Applications of warp knitted fabrics are extensive, ranging from garments, underwear, and hosiery to medical and sanitary textiles, sportswear, furniture upholstery, car industry components, technical products, fishing nets, packaging, geotextiles, and agricultural textiles.
Advanced Knitting Techniques and Seamless Technology
Modern textile machinery has pushed the boundaries of knitting, enabling sophisticated techniques like seamless production and the creation of specialized fabrics.
Seamless Technology: A Revolution in Garment Production
Seamless technology aims to produce garments with minimal to no sewing, eliminating bulky and irritating stitches. This offers numerous advantages:
- Freedom of body movement: The absence of seams eliminates elasticity differences, allowing for unhindered movement.
- Wider range of fit: Seamless garments can accommodate diverse body shapes.
- Inherent softness: No annoying stitches at underarm points, shoulders, or necklines, providing a soft feel.
- Reduced labor cost: Elimination of cutting and sewing processes significantly lowers labor involvement.
Both warp and weft knitting approaches contribute to seamless technology.
Warp Knitting Seamless (WKS)
Highly innovative, WKS produces items from t-shirts and lingerie to gloves, tights, and sportswear. The RDPJ and DJ machine series are ideal for seamless goods requiring minimal make-up. Two-bar raschel machines are particularly effective, creating:
- Tubular shapes with variable diameters for a perfect fit.
- Functional zones with different stretch values.
- Seams worked directly into the garment.
- Open-work and jacquard designs.
- Different patterns for the front and back of a garment.
For example, an RDPJ 4/2 machine with a working width of 138" and E 24 gauge can produce three long-sleeved shirts in one fabric panel using core-spun and standard yarns (81% PA 6.6 and 19% elastane). Warp knitting offers a higher loop production rate than weft knitting for seamless products. Karl Mayer's DJ 4/2 EL machine, with a gauge of E 32 and a working width of 44'', can achieve a production rate of 750 courses/min for seamless articles. Santoni's SWD 4/2J and SWD 6/2J are compact electronic double needle bar warp knitting machines for seamless items like pantyhose, underwear, and sportswear, featuring structures for breathability, non-run properties, mesh areas, and body mapping with compression.
Weft Knitting Seamless
Weft knitting machines also offer seamless production. The Santoni SM8-TR1, a single jersey machine (up to 24 gauge, 110–160 rpm), provides eight feeds for knit-miss-tuck, fishnet, anti-drop stitch structures, and patterned fabrics with floated yarn. It can work with natural yarns (wool, cotton, linen) and synthetics, producing double fabrics, plating, mesh, pointelle, or eyelet areas. The SM-DJ2TS is a complete double jersey circular machine for seamless garments and sweaters (e.g., 18 gauge for seamless, 15 gauge for sweaters), knitting various manmade and natural fibers for true ribs, links-links, jacquards, striping, pointelle, eyelet, and body rib bands.
Make-Up Operations for Seamless Products
While seamless technology minimizes post-knitting work, some make-up operations are still involved:
- Step 1: Warp knitting: Machines like RDPJ and DJ series produce goods requiring very little make-up. The process directly incorporates features like tubular shapes, functional zones, and patterns.
- Step 2: Finishing: For conventional seamless articles, tubes and stockings are typically finished individually by pulling each piece onto a special frame, then processed through units for drying, steaming, and hot-air heat-setting. However, tubular finishing is not ideal for elastane-containing knitted fabrics due to limitations in processing zones, achievable temperatures, and process reliability.
Comparison: Seamless Warp vs. Weft Knitting
| Feature | Warp Knitting (Seamless) | Weft Knitting (Seamless) |
|---|---|---|
| Yarn Supply | Warp sheet on beams | Cones produced on winding machine |
| Tubular Product | Different diameters, max. according to machine bars width (44"). | Diameter according to machine diameter (16–20"). |
| Machine Types | Several types for whole product range | Limited types for specific diameters |
| Set Up | Cut edges, small curling | Set up with inturned welt |
| Product Closing | Closing in the machine (needle bed) | No closing, sewing is necessary |
| Speed Reduction | No speed reduction for product closing or set up | Speed reduction may occur for product closing or set up |
| Loop Production Rate | Higher | Lower |
| Simultaneously | Knitting pieces (sleeve–body–sleeve) | Knitting only the body, other parts cut-and-sewn |
| Jacquard | Unlimited patterning in whole product | Unlimited patterning in whole product |
| Laddering | Less disposition to laddering | Prone to laddering |
| Preparation | Preparing bars after warps run-in | Commencing knitting on empty needles |
| Pattern Changes | Easy, small batch production of various size product | Easy, small batch production |
Transferring Loops in Weft Knitting
Transferring loops is an advanced technique in weft knitting, especially in V-bed flat and circular machines. This allows a loop held in one needle to be transferred to an adjacent needle on the same needle bed. Historically, transferring a loop from one needle directly into its adjacent needle on the same needle system was only possible in straight bar weft knitting machines. This technique uses special needles with a wing in the stem, enabling the loop to be enlarged sufficiently for transfer. It facilitates creating small holes in the fabric without curling. The limitation is typically transferring up to three or four loops between adjacent needles in the same course without breaking the yarn.
Spacer Knitted Fabrics: Structure and Production
Spacer fabrics are innovative three-dimensional textiles, often described as a