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Efficient air-jet system for combed cotton yarns

Oct 01, 2020
Efficient air-jet system for combed cotton yarns

There is increasing demand for air-jet yarns in the textile chain. With the system from Rieter, they can be produced economically. The air-jet spinning machine J 26 offers advantages in terms of the yarn characteristics too. Low fibre fly in weaving and knitting and fabrics with pleasant soft touch are further strengths of this yarn. Customers who choose the Rieter air-jet spinning system generate an approximately $1.8 million higher cash flow per year in comparison to customers who use spinning systems from other providers.

Air-jet yarns and the knitted and woven fabrics made from them are one of several interesting trends. Air-jet spinning offers many unique advantages. For example, air-jet spinning machines offer the highest yarn production capacity of all spinning machines. Staple fibres are made into yarns at up to 500 m per minute. This is roughly five times the rate of a rotor spinning machine and 20 times the rate of a ring or compact-spinning machine. Yarns produced on an air-jet spinning machine have the lowest hairiness. Fabrics made from these yarns have an extremely low pilling tendency, and the end product offers maximum shape retention.

Rieter offers a complete system for producing air-jet yarns from a single source with the blowroom line VARIOline, the SB and RSB draw frames, the combing preparation OMEGAlap E 36, the combers E 90 and the air-jet spinning machines J 26 (Fig. 1). A comparison between a Rieter system and a “mixed system” consisting of machines from different manufacturers demonstrates that the investment is worthwhile. A combed cotton yarn with a yarn count of Ne 30 was spun using the sequence of machines shown in Fig 2. Both systems each produced 1 345 kg of yarn per hour.

Fig. 2:The following process sequence was selected for comparison.

Optimal utilisation of the raw material
One of the top priorities when developing Rieter machines is good raw-material utilisation. The two recently published articles about compact-spinning systems and rotor spinning systems showed that the fibres are optimally fed and processed in all machines in the Rieter spinning mill line. The same is true for the Rieter air-jet spinning system, which utilises the raw material efficiently thanks to the top-quality fibre preparation in the blowroom line VARIOline, the efficient noil extraction on the comber E 90 and the optimal fibre feeding in the spinning unit of the air-jet spinning machine J 26.

During air-jet spinning, the yarn is twisted using an airflow. One third of the fibres lie parallel in the core, and two thirds of the fibres are wound around it. This creates the typical yarn structure (Fig. 3). Fibre feeding in the J 26 is designed so that up to 50 per cent fewer fibres are lost in comparison to other air-jet spinning machines. When using 100 per cent cotton, this means that 3 to 4 per cent (absolute) more fibres are turned into yarn than with the “mixed system.” This value is impressive, as the raw material is the biggest cost factor in yarn production.

Fig. 3: The typical yarn structure of Com4jet, the yarn produced by the air-jet spinning machine J 26.


Sustainability through energy savings
The end-spinning machine is the highest energy consumer in the whole spinning process. Savings here therefore have a particularly significant effect on the energy balance. On the J 26, the spinning and winding units are equipped with energy-saving individual drives. When a spinning position is not in use, it consumes neither energy nor compressed air. Furthermore, the energy required to generate the underpressure is constantly monitored. If the set limit value is exceeded – for example if the filter needs cleaning – a warning notice is issued. The operating personnel can react quickly. This allows energy savings of up to 15 per cent. On the J 26, the suction along the machine is divided into zones.

The underpressure is controlled according to the distance to the compressed-air fan. This is very efficient, especially on long machines with up to 200 spinning positions, yet stable air conditions are still ensured over the entire length of the machine and energy savings of up to 5 per cent can be made. Energy-efficient drive concepts and innovative machine components in the blowroom line VARIOline and the spinning preparation machines (i.e. the card, draw frame and comber) also play a part in keeping the energy costs per kilogram of sliver produced low. Energy savings of up to 16 per cent can be made across the entire system.

Significantly Lower Space Requirement
With the powerful cards and combers, the compact draw frames and the high productivity of the J 26, which can produce yarns on both sides, a Rieter system requires significantly fewer machines and consequently 25 per cent less space than other systems. In this comparison, seven cards, six draw frames, two combing preparation machines, six combers and 41 per cent space at the air-jet spinning machines can effectively be dispensed with. This reduces the space requirement by 3 500 m2. The special feature of the J 26 is that the cans are stowed in a space-saving manner underneath the drafting unit. Can formats with a diameter of 500 mm and a height of 1,200 mm offer sufficient volume for the draw frame sliver and reduce the number of can changes.

J 26 offers flexibility and quality
The design of the air-jet spinning machine gives it many advantages. For example, the machine has two sides that work independently, which makes it possible to spin two yarns of different qualities at the same time. Independent tube loaders with different-colored tubes and separate package conveyor belts enable the two assortments to be handled separately and make the work of the operating personnel easier. Another advantage is the placement of the cans under the drafting unit. This not only saves space, but also minimises the distance that the sliver has to travel from the can to the drafting system. This is the only way that drafting faults can be avoided and a consistent yarn quality guaranteed.

Customers want either a cylindrical or a conical package depending on their intended application and principles. The J 26 offers both. Furthermore, yarn packages of different hardnesses can be made thanks to the individual drives at each winding unit. This allows soft dye packages to be produced directly on the machine, which avoids the need for time-consuming rewinding. Winding the yarn using “true anti-patterning” prevents threads in multiple successive winding layers from lying on top of each other or parallel next to each other. This is the only way to achieve perfect, even package build-up and thereby optimal unwinding behaviour in the following process.

Highly Productive Machines Require Fewer Personnel
In many markets, spinning mills are being confronted with a growing labour shortage and a lack of industry-specific expertise. The ability to achieve the same yarn production with fewer personnel is therefore highly valued. The Rieter system requires fewer machines than the “mixed system” to achieve the same production volume. This results in personnel savings of around 14 per cent.

Earn More Money
Taking all of the cost advantages mentioned above into account, the total production costs of the Rieter system for the combed air-jet spinning process are lower than those of a “mixed system.” Customers who choose the Rieter air-jet spinning system generate an approximately $1.8 million higher cash flow per year at the same production volume (Fig. 4).

Fig. 4: Customers who choose the Rieter air-jet spinning system generate an approximately USD 1.8 million higher cash flow per year.

Unique Advantages for Downstream Processing
The J?26 can produce yarns with Z- or S-twist. This gives the knitted fabric considerable advantages. By alternately feeding Z- and S-twisted yarns, the knitted surface becomes dimensionally stable and the touch becomes very soft. Using both yarn twists also ensures that the goods – an especially their side seams – are not affected by spirality even after several washing cycles (Fig. 5).

Fig. 5: The J 26 produces Z- and S-twisted yarns. This is the only way that spirality of the knitted fabric can be avoided.

In weaving mills, the air-jet yarns are impressive thanks to their very good size pick-up. This reduces the amount of sizing agent needed and therefore the costs. The fabric is washed after weaving, whereby, thanks to the lower quantity of sizing agent, the cleaning of the waste water is less intensive and thus more environmentally friendly. The low hairiness of the J 26 yarns also reduces the fibre fly during weaving. This minimises deposits on the weaving machine and reduces the cleaning effort. The machine running times increase. Products with high-quality character
Fabrics produced from the J 26 yarn have a unique colour luster. The surface is very even, which is primarily based on the low hairiness. This is the ideal prerequisite for printing on fabrics too. The contours become extremely clear and defined. Overall, end products such as t-shirts, sweaters and terry towels have a very high-quality character. The products also impress in daily use: High resistance to pilling and washing (Fig. 6), maximum shape retention and intense colors – even after frequent washing – ensure a long-lasting and therefore sustainable product.

Fig. 6: The air-jet spun yarn Com4jet made of 100% combed cotton of the count Ne 40 shows an outstanding pilling behavior.

Rieter is the world’s leading supplier of systems for short-staple fibre spinning. Based in Winterthur (Switzerland), the company develops and manufactures machinery, systems and components used to convert natural and manmade fibres and their blends into yarns. Rieter is the only supplier worldwide to cover both spinning preparation processes and all four end-spinning processes currently established on the market. Furthermore, Rieter is a leader in the field of precision winding machines. With 16 manufacturing locations in ten countries, the company employs a global workforce of some 4,570, about 21 per cent of whom are based in Switzerland.