Weft knitting is gradually becoming more-n-more popular because of low cost of production, excellent output turnover and different varieties.


Knitting can be described as making a fabric from loops of yarn. Knitting by hand is an ancient art. Nobody knows where from it originated and when. It is assumed that people of Persia were the inventors, who were very much fond of art. But of course countries like Israel, Jordan and Syria may also have developed the craft that use weft knitted fabrics and so also the North Africans: mainly the regions which are traditionally Islamic belt; nothing to do with the religion though. Perhaps weft knitting is symbolized by their attire more than others for its origin.


It has been assumed from ancient paintings that it was mostly worn by the women of the Middle East during the late eighteenth and early nineteenth century. Other things which were knitted traditionally were pullovers, cardigans, skirts, men's under�wear, sportswear and swimwear. The advent of knitting machines enhanced the speed of production and designs. The machine also offers great range of designs and patterns. Now, computer chips have been introduced to control the machines, which allow permutations with designs. At present, people have accepted the knitted cloths as everyday-wear.

Population has increased and so is the demand for more cloths, which leads the textile industry to evolve rapidly. Knitted fabrics are one of the most fashionable cloths, with the advantage of offering variety of designs, which make every cut of cloth a unique look.

Yarn quality decides the excellence of the finished product in every weave. When there are more broken ends, the quality deteriorates, if it is continuous in length then the odd tiny mounds in the cloth will not be there giving it a smooth finish. So it is said that good quality winding is one that produces few broken ends, and contributes in the finish quality of the cloth. The yarn that is available in today's market is of average quality, so the machines have been upgraded to make best most out of whatever available yarn.

Weft knitting and weft fabrics are classified as single or double depending upon the number of the self-regulating needle sets necessary to make them. Industrial weft knitting machines are either flat-bed or circular machines.

Weft knitting and warp knitting are two ways of forming a knitted fabric. The following points will be highlighting the developments in particularly weft knitting sector.


Creel Unit

In creel section there are procedures like package mounting, feeding of the yarn etc, but the major part is affected by fly removal system. The fly removal system is mounted at one end of the creel, which takes care of the fly which affects the quality of the finished product. Lot of them will also affect production thereby jamming the entire running.

To prevent this, a tube is provided which is stretched from the start of the yarn mounting place up to the wheel that feeds the threads in the formation of the cloth. This way the production quality does not deteriorate.

The air is compressed for threading, and the material is bit polished, which offers very less friction that maintains thread quality. Packages are to be changed often for patterns, but this may interfere with the enclosure and the process becomes cumbersome. Of course, if changed at a ceasing frequency, then it can be a little easy. In that case, the heavy package would serve the process. Presently the weight of the package is around 2 Kilos.


Yarn Feeder

The yarn feeder pulls out the yarn from the package and adjusts it, so that the needles are placed with uniform tension for knitting. This is the only job the yarn feeder does. Yet, this is where the onus of the product quality lies. It is very essential that the tension is maintained uniformly, as the length of yarn per stitch has to be unique for the whole length of the cloth. Machine quality is also responsible for the uniform pulling of the yarn length.

There has been a lot of improvement done with the yarn feeders, but the basic concept has been sustained. The machine has attained super efficiency with its improved feedwheel and the tensioner. The present day's super-positive feedwheel with yarn tensioner, with a motion stopper, along with multiple looping has increased efficiency. Less or nil amount of slippage helps the cloth quality to upgrade.

Latest positive feeders for circular knitting are easy to navigate, needs less maintenance and are quite durable. The whole unit is housed with a plastic cover, and is very light in weight, results in less vibration and elimination of static charge. Some of the machines have electronic controls with enhance yarn feed process.

Materials used in the spooler are always being researched so that filamentation is less in amount. The coating is hard to resist corrosion and wearing off. A clutch is provided with open-design, which is helpful while cleaning. The ceramic yarn guide prevents short circuiting of the vibration tensioner that contains magnetic rings. All these mechanism is to ensure perfect tension.

For irregular or intermittent feed the yarn feeders have to stop periodically in between the weave as in case of the jacquard machine. All these specifications have been achieved in the storage yarn feed, developed by IRO.


Cam and needle

The most important part in the knitting machine is the cam unit. The machine efficiency looks after design and the quality of fabrication. The cam and the needle which have been arranged as the cylinder and the dial move in unison to move the needle which makes them involved with the knitting process in more direct manner. The back up system ensures that there are almost double knitting arrangements. It makes knitting a no trouble operation.

Cam boxes that have been manufactured by Amtek, using high strength perunal alloy, are good conductors of heat which implies that heat is removed promptly from the system.


Needles

The needles that weave smooth patterns are very delicate in nature that can withstand certain amount of tension but not much. Designing is very important part, so that the needles work for longer. Various parameters for the making of needles to resist different fabrics are: modern improved surface quality, head geometry, heat treatment and shape of the shank.

With circular stitching styles, the bending of the needles is the main problem. The needle hooks are made circular for this kind of stitching. To increase efficiency of the needle without compromising the space for the yarn, designers have devised the cone-shaped needle hooks. The shank design holding three needles have been improved geometrically to take care of the machine vibration.

A needle with special latch and extra sawslot for smooth operation with rest surface at the back of the latch was designed by Groz Beckert who has been manufacturing needles for years. At the end of the latch there is a spring that helps regulating the tension.


Sinkers

The sliding movement provided by the sinker supports the loop. Sliding may cause friction. This is where the concept of improving the surface quality has come into play. The curves have been properly designed and there is surface finish. The yarn tension is reduced with this design.

Terrot has developed a sinker that has double edge, each of which is controlled by separate mechanisms. The parts are; a knock-over sinker for loop doubling over, and an insertion pusher plugging over the yarn space.

The plush sinker is there for the adjustment of knitting needles and the production of pattern plush fabric, which has been another designer forte of Terrot.


Take-down

For uniformity stitching operation and the fabric provision and the acceptance of the machine to pool it for the weave should be matching for the quality finish. The tension has to be almost one everywhere throughout the circumference of the unit. Uniform tension however is attained with difficulty because the fabric comes in a circular pattern to be placed as double layered straight fabric bed on the take-down roller.

There is an open-width fabric cutter and take-up with black-and-white Lycra wheels appearing gray as long as the fabric is running and clear black and white when the yarn breaks. This helps in enhancing fabric take-down performance. The centre puncturing of the roll is ceased, and the calculation is done with EPA for even take down and rolling of yarn for without a crunch for the entire width of the fabric.

Stop and start in batches

The knotted fabric is rolled so that it can easily transport for further procedures. For machine efficiency, however, there is less number of rolls so the roll size is high (there is a restriction on the dimension size of a yarn) or the various rolls are many, which come into play one length after the other which improves efficiency of the machine. This is clearly a batch of arrangement for the feeders.

The Synchronised Take-down Plaiting Device (TOP) with speed adjusting VDQ pulleys designed by the Shelton, smothers the conic fabric carefully into a box. The box is transported to the Shelton Verifab SR where the box slits, opens, inspects and the fabric is re-rolled into the machine where the Verifab SR machine removes the curl with its three de-curling stations before the re-rolling. Most circular knitting machines have easily fitted TOP. Plaiting function of the machine also allows larger batch sizes.


Drive

The latest machines uses frequency controlled asynchronous motor with digital control system for smooth inching, breaking and speed with stoppage at times.


Control systems

The common features are
. Modern consoles as display panels
. Digital control systems
. Centralized lubrication systems
. Stop the motion when the thread is broken

This way the computer is brought into the picture for efficiency and improvement in quality.

In case of pattern design: Pattern selection and striping are also available now-a-days.

Microprocessors have been used with Germany-based Mayer & Cie offers Pattern Information Center (PIC) 4, which includes features such as:
. More desktop icons for other functions.
. Direct screen access to the color palette.
. Permutations of patterning for transfer knits.
. A pattern editor combines and edits a pattern using 16 colors.
. A repeat editor does four different patterns to be put as templates for simultaneous knitting.
. An optional striping editor includes other patterns in addition to the established four colors.

The system is available in English, German, Protugese, Chinese, French, Turkish and Spanish. The required operating system is Windows, 8 MB RAM and a Pentium processor.


Development news

Following are few more development news, apart from the above.

Mayor and Cie introduced Relanit 4.0, featuring has four feeders per inch to give a speed factor (rotational speed x Diameter) of SF 1500. They have also raised fabric rolling up to 1200 diameter. Breaks are introduced at every yard breaks. A precision controlled break avoids vibration.

For faster change in fine gauge machines, open width take down with quality has been developed by Terrot.

Four track feeders for every cam box instead of the three track feeders have been introduced by Santoni, which helps in easy cam replacement.