The prerequisite for weaving a great fabric is spinning a
good yarn. In fact 'a good yarn' is catch phrase of anyone involved in textile
industry. Yarn structure is one of the basic factors that control the
properties of spun yarns. Immediately after the invention of the spinning mule, the textile
machinery industry has been working relentlessly in the direction to develop
faster and more reliable and flexible spinning technologies. Air-jet spinning
is the latest endeavour in the same direction.
With time, Air-jet spinning has found a niche market for the special yarns and this technology has also been successfully adopted by several companies. Modifications in the Air-jet technology resulted in noteworthy modifications in yarn structure. These modifications enabled twist to be imparted more effectively to the outer surface of the yarn, which, consequently, increased yarn tenacity. Today it is also possible to process shorter staple lengths, such as cent percent cotton, in addition to man-made fibres and blends.
The basic requirement of a successful spinning machine for yarns includes a good quality drafting system, twisting device, a take up unit and the most important is the ability to afford some control over the quantity and distribution of wrapper fibres created on the yarn surface, since this ultimately controls the yarn quality. This was a deficient in the previous Air-jet spinning machines which has now been overcome with intervention of the modern Air-jet spinning technology.
In comparison to methods wherein the productivity is limited by the twists in yarn, Air-jet spinning ensures that regardless of yarn counts, the yarn is produced at a relatively high production rate. The Air-jet machine consists of one or two fluid nozzles, drafting system and a take up device.
The manufacturing process of yarns under Air-jet spinning
is as follows:
- The first step
is to pass drafted strand of fibres through the single fluid nozzle or (in case
of two nozzles), through the double nozzles.
- These nozzles
are positioned between the front roller of a drafting system and a take up
- In case of
double nozzle system, the drafting system drafts the input material into a
ribbon like form with parallel fibres.
- Subsequent to
this air is injected at a very high pressure into the two nozzles.
- The high
pressure swirls the air stream in opposite directions.
- After this silver is inserted into the machine and again high pressure air is injected to attain twist.
The fibres at the end of the ribbon are not given complete twist like the main body fibres. This is done to ensure that these fibres are less twisted than the fibres in the main bundle.
Thus, when the
yarn is untwisted in the downstream of the twister, the low twist edge fibres
get untwisted to a greater extent than the original twist. Consequently, they
are given precise twist in the track opposite to that of the upstream twist.
- The main body
of the strand will be untwisted into parallel fibers, forming the core and
these will be wrapped around by the edge fibers forming the wrapper fiber layer
or the sheath, thus forming a perfect yarn.
- The function of the back nozzle is to enhance the structure of the strand thus giving greater yarn strength. Since the direction of airflow in the back nozzle is opposite to that of the front nozzle, the back nozzle tends to untwist the wrapper fibers as they are formed inside the front nozzle. This increases the length of wrapping, thus improving the yarn consistency and strength.
Double nozzles are considered to be superior to single nozzle in yarn spinning. Air-jet spinning is a miracle for yarn manufacturers as it gives an opportunity to produce yarn at relatively high production rates. The earlier obstacles of air-jet machinery like difficulty to make cent percent cotton yarns and the generally harsh hand of the fabrics produced from them have been overcome. Air-jet yarns are smoother to the touch because of the absence of wrapper fibers and improved fiber alignment.
However, application of this technology depends on the spinning yarn counts. If the yarn count is coarser than English Cotton Yarn Number (Ne) 12/1, then Air-jet spinning will not work. Air-jet spun yarns are mainly produced in the medium count (30 Ne) range and are mainly polyester/cotton blended yarns. Air-jet yarn often has one primary drawback over the ring yarns produced from the similar fiber properties i.e. the Air-jet yarns lack tenacity. Apart from this, another concern is that of waste percentage. Under this system considerable amount of short fiber is removed, which leads to waste ranging between 3 and 8 percent, depending on the type of cotton (combed or carded) that has been used. In addition, Air-jet yarns can be made with varying levels of hairiness that can directly influence the fabric's softness while maintaining excellent resistance to pilling and abrasion.
Air-jet spinning creates functional and fashionable yarn. The Air-jet incorporates three processes i.e. roving, spinning and winding and in some cases it incorporates four processes i.e. roving, spinning, winding and doubling. It is user-friendly in operation management and quality control. The spinning speed is of 340m/minute and it saves space, labour and energy.
The Air-jet yarns have less hairiness and are clear in appearance. Evaluating the yarns produced by other methods and Air-jet yarns reveal that the later show considerable resistance to pilling and abrasion. Yarns spun by other methods, moisture absorption and wash resistance properties are lacking, whereas Air-jet spun yarns display high moisture absorption and wash resistance properties and comparatively less shrinkage. Another advantage of Air-jet yarns is that materials such as cotton, synthetic fiber, regenerated fiber and blended fiber can be employed to produce perfect yarns. The structure of Air-jet yarn makes it a perfect choice for core yarn.
The latest Air-jet spinning technology produces new yarns with new yarn characteristics, and opens new market opportunities for spinning plants. Yarn formation is achieved by turbulence with an airflow in a spinning nozzle, which creates a quite different yarn structure. A company in Switzerland claims that its latest machine in Air-jet spinning series is a production miracle with smallest space requirements. With its high operating speed of up to 450 m/min and 120 spinning units, the new air-spinning machine heads the productivity scale.
The newest technology in Air-jet spinning is available in Switzerland. Countries like India, Japan, European countries and the United States of America are laying emphasis on use of improved technology in textile sector, so application of Air-jet spinning is common in these countries/regions.
The difference in quality of yarn directly affects the quality of woven fabric. Air-jet spinning is a perfect way to produce the best quality yarn in limited set of time. The benefits of this technology have made it a first choice of several textile houses everywhere in the world. With research going on in this direction, Air-jet is likely to improve further in time to come.