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Features

ITMA Technology: Circular And Warp Knitting

Trevor J. Little, Ph.D., Technical Editor

Knitting technology continues to expand the capabilities for conversion of fiber and yarns into knitted products. This review of ITMA 2011 looks at major developments that knitting machinery firms are planning to advance the state of the art. Obviously, there are developments that have improved capabilities such as production speed and production efficiency, and Textile World will review several examples. Other developments continue to push the limits of technology still further in the relentless pursuit of finer and finer fabrics, but these developments are clearly focused on one firm — Groz-Beckert KG. Then, TW got to see the knitting inventors that continue to integrate parts of the process that heretofore have not been accomplished.

Gauge
The finer and finer gauge is being pursued by both the circular and warp knitting sectors. Finer gauge means finer and more reliable knitting components — especially needle beds, cylinders and needles. Last ITMA saw the introduction of a 60-gauge circular knitting machine, and this has since found application in performance fabrics for activewear. This ITMA, Santoni S.p.A., Italy, showed an 80-gauge machine. The Santoni Atlas was operating at a 30-inch diameter and 80 needles per inch, with a total of 7,536 needles in the cylinder. At these finer gauges, there is not space for the traditional sinker, so the sinker has been eliminated and replaced by special holding-down jacks. This has the added advantage of avoiding the creation of sinker lines, which can be a problem when knitting fine-gauge.

SantoniAtlas
The Santoni Atlas 80-gauge circular knitting machine's patented system uses Groz-Beckert technology and produces a tighter knit compared to traditional knits.

Germany-based Groz-Beckert showed another fine-gauge machine with 80 needles per inch. The company has developed the ability to make needles that knit at normal knitting speeds and also has the technology to make cylinders that can accommodate the finer-gauge needles. Groz-Beckert and Santoni are working on a 90-gauge machine in 30-inch diameter that has 8,472 needles and 88 feeds. Groz-Beckert had on display a 90-gauge cylinder for which the needle width is only 0.18 millimeters.

It may also be interesting to note that Groz-Beckert has developed a cylinder removal tool called CylinderMaster, designed for machines with diameters larger than 26 inches. The main purpose is to be able to remove cylinders easily as well as prevent handling damage, especially for the finer-gauge cylinders.

Mayer & Cie. GmbH & Co. KG
, Germany, showed the MJ3.2 E DNS 60-gauge jacquard — claimed to be the first fine-gauge jacquard machine, according to company representative Axel Brunner. The machine with 48 feeds and 30-inch diameter operates at 20 revolutions per minute (rpm) and has the standard three-way knitting technique. It is equipped with the open-width fabric system to avoid center creases on these fine-gauge fabrics. Mayer & Cie. also has introduced temperature control for the knitting zone by using a water-temperature-controlled system to ensure precise and reliable needle selection mechanisms.

Warp knitting machinery manufacturers also showed interest in developing finer-gauge equipment. Karl Mayer Textilmaschinenfabrik GmbH, Germany, exhibited a 50-gauge tricot machine, HKS 2-3 E, operating at 3,200 rpm and producing elastomeric fabric using 20-decitex spandex and targeted for the lingerie market. According to Tim Wollnik of Karl Mayer, this is the first and finest-gauge tricot machine. He said this is the type of machine used by firms such as Belgium-based NV Marcel Liebaert for its lingerie fabrics.

Of course, one should compare the production rates of weft and warp knitting, and one way is to look at the number of knitted loops produced each minute. For the 90-gauge Santoni 30-inch diameter operating at, say, 30 rpm and 88 feeds, the machine produces 22,366,080 loops per minute. Karl Mayer's tricot with 130-inch width, 50 gauge and 3,200 rpm produces 20,800,000 loops per minute, or slightly less than the number of loops per minute for the fine-gauge weft knitting machines. Clearly, there are additional factors that dictate knitting system choice, but one can expect the loop production rate to increase as finer gauges and higher speeds occur. However, for fine-gauge knitting, warp and weft loop production rates converge.

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Improved Production Rate And Efficiency

Improved production rate has come from higher speed almost across the board. Vanguard Pai Lung LLC, Monroe, N.C., showed its SJ4A-DI3 Super Jumbo machine operating at 1,750 speed factor, which is 58 rpm for a 30-inch-diameter machine. This speed factor applies for machines in the 14- to 24-needles-per-inch range, and 1,500 speed factor for 28-cut machines. The SJ4A-DI3 employs a closed-cam track system that ensures positive needle control and provides consistent stitch definition. The jersey machine is equipped with angular sinker technology to improve fabric quality and lower the defect rate, even at the highest speeds. The Delta machine is equipped with a patented three-level sinker cam designed for high-speed knitting. Vanguard has also increased the size of the fabric roll that can be produced to approximately 500 pounds. This size enables batch processing of the fabric with a single doff and without the need for bolt-end seaming in finishing, according to Matthew Yates of Vanguard Pai Lung. Vanguard also showed high-speed 4-inch-diameter rib and 5-inch-diameter jersey machines. These small-diameter machines are made for production of fabrics used in the apparel, industrial, medical and packaging industries, Yates said.

Mayer & Cie. has improved the Relanit 4.0 to achieve speeds of up to 70 rpm, according to Brunner. Relanit 4.0, with four feeds per diametrical inch, is available in gauges from 18 to 28 and in diameters from 24 to 36 inches. A 15-inch-diameter machine is available on request. As a component of improving productivity, the Relanit has been equipped with the Mayer Cleaning System, which uses ambient air to provide a cam cleaning role as well as to keep lint and dirt from entering the cam and needle area. Improvements have also been made to the positive feed system for the knitting yarn. The fabric take-up system can accommodate a 230-kilogram roll, allowing a longer knitting time between doffs.

Mayer & Cie. also showed a new striping machine that efficiently produces striped or basic fabrics on the same machine. According to Brunner, the S4-3.2R produces striped fabrics in four and six colors across 1.6 feeds per inch. As long as all feeds are striping, the machine uses 1.6 feeds per diametrical inch. However, if a part of the fabric is non-striped, those feeds can knit with 3.2 feeds per inch; or when striped fabrics are not needed, the machine can produce basic fabrics using the 3.2 feeds per diametrical inch. This approach provides an optimized solution for increased production as well as a more flexibly configured knitting system. The S4-3.2R is available in 24-, 30-, and 34-inch cylinders and from 18 to 36 gauge.

Mec-Mor
, now included in the Santoni Group, showed a circular machine in 14 gauge as part of its move to sportswear, according to Patrick Silva Szatkowski, marketing manager for Santoni. This machine can produce fabric for one polo shirt in 3.5 minutes, making it one of the most productive sportswear fabric machines, he said.

Mattress Ticking Machines
The use of knit fabrics for mattress ticking continues to be an important market for knitting machine builders. Mayer & Cie.'s OVJA 1.6 EM and 1.6 EE machine models have been configured in larger cylinder diameters — including 38 and 42 inches for the OVJA 1.6 EM, and 48 inches for the OVJA 1.6 EE — in gauges from 18 to 20 for the OVJA 1.6 EM and 18 to 28 for the OVJA 1.6 EE. While both models are electronic, the OVJA 1.6 EE has full electronic control of both cylinder and dial needles. The short changeover time offers the possibility for smaller batches, according to Brunner, as well as the production of large batches when applicable.

Terrot GmbH
, Germany, showed model UP592M, a 38-inch-diameter 20-gauge machine using a mini-jacquard selection system on the cylinder, for knitting mattress ticking. This model typically can produce 60.9 meters per hour of mattress ticking fabric weighing 282 grams per square meter.

Knitting machines for mattress ticking are getting larger in diameter to satisfy the width requirements for the larger-size mattresses.

Seamless Knitting
The Santoni Group has continued to advance knitting technology and offered many examples of new ways to make seamless garments. Santoni model SM8-TR1 now offers transfer on a single-jersey machine. Other knitting capabilities are available thanks to the eight feeds on the same course, including knit-miss-tuck plus fishnet or anti-drop stitch structures or pattern with floated yarn. The set-up can be two technical ways — such as knit and miss — plus fishnet or anti-drop structures with the possibility of inlaid knit work on all feeds. The capability of the machine is limited only by the imagination of those fortunate to work with one.

Of special interest in the small-diameter knitting sector was Italy-based Sangiacomo's model HT2 for the production of true heel-and-toe socks. The HT2 is a two-feed, 3.75-inch or 4.0-inch machine with eight striper units and eight electronic needle selection stations so that the designer can have individual needle selection on any part of the sock. The machine produces a sock every 2 minutes 15 seconds. The special development from Sangiacomo is the onboard toe linking unit, according to company representative Sergio Zanoni. Once the sock is knitted, it is turned and placed on the onboard linking unit, the toe is linked, and the completed sock is ready. Although the toe-closing operation has been substantially automated, it still involves operator loading and a separate batch process. This new development of onboard linking offers an integrated approach and combines and automates several labor-intensive steps at the knitting stage.

While warp knitting has had technology to produce garments for some years, there is evidence that this approach is receiving new attention. Karl Mayer showed Model DJ 6/2 with six needle bars in 44-inch width and 28 gauge for the production of jacquard seamless garments and shapewear by selectively placing elastic in areas of the garment that require extra support. Santoni also showed its warp-knit seamless machines including SWD 4/2J four- bar and SWD 6/2J six-bar 44-inch-wide machines in 24 gauge. As noted earlier, there are productivity gains if a portion of the seamless market can be converted to double-needle-bar warp knitting when the loop production rate is higher for a warp-knitting approach than for a weft-knitting approach.

More Integration
In addition to the type of integration offered by Sangiacomo, other knitting machine producers showed integration from a different perspective. Mayer & Cie. is developing a machine, dubbed spinitsystems, that backward-integrates into the spinning process (See "ITMA Technology: Staple Spinning,"). The circular single-jersey machine houses roving bobbins in the place of yarn packages and spins the yarn on the knitting machine, Brunner said. The spinning system is air-jet and can spin yarn from 40 to 70 Nm. As is well-known, yarn delivery speeds from air-jet spinning systems can reach 450 meters per minute, which far exceeds the rate of yarn demand by a knitting zone. The machine is equipped with sensors that detect when the roving runs out, and it can electronically remove that feed from knitting until the new roving is in place and producing yarn again. A yarn vacuum system prevents unused yarn from contaminating the other knitting zones or the fabric. The concept has merit — especially the flexibility to change yarn size both within the fabric and between fabric styles. Further, it offers the capability to produce short runs with a designated yarn size or as a R&D tool for fabric development. Equipment to produce or transport roving is needed to be able to load this type of knitting machine, and a reliable supply of air is required to operate the spinning system.

Vanguard Pai Lung has also entered this area of integration and has built a machine that uses sliver instead of roving. The machine was at ITMA, but behind closed doors.

Clearly, this type of integration heralds a new era for the entire textile complex, especially the ability to spin on the knitting machine. This raises the question as to whether spinners will become knitters or knitters will become spinners. Either way, it's time to build a strategic model for knit fabric production as the industry goes forward.


More To Come
Advances from the knitting sector continue at an impressive rate. In addition to the innovations highlighted in the circular and warp knitting sectors, there were many additional developments at the exhibition, and those merit a separate discussion that will be included in a future issue of TW.


November/December 2011