Detailed knowledge and understanding of the fiber raw material is critical to achieving the best possible quality in the yarn. To help spinners, Uster experts have put together guidelines for avoiding yarn irregularity claims, in a special edition of the Uster News Bulletin No. 52.
Laydown consistency – use data correctly
One factor which greatly impacts the spinnability of cotton fibers, as well as the yarn quality, is fiber fineness. Cotton has inherent natural variations, so fiber fineness (micronaire) is therefore a key parameter to be controlled within required limits.
Optimal bale mixing aims at a consistently narrow micronaire range. Minimizing variation in micronaire values, both across and within laydowns, is critical. Fluctuating micronaire values can lead to barré or inconsistencies in yarn strength, causing quality claims. To reduce the risk, spinners use data from Uster HVI for laydown management. Taking it further, many mills have integrated automated solutions such as Uster FiberQ, with algorithms that control not only micronaire but also multiple other fiber characteristics. This reduces manual work and can contribute to improved long-term quality from fiber to yarn by refining raw material selection.
Fiber process control – look closely at the blowroom
Uster’s experience shows that the reduction of neps is another of the most frequent challenges for spinning mills. Here, it’s better to avoid creating neps at the beginning of the process, instead of trying to reduce them in spinning. Many spinners take steps in the blowroom and carding processes to tackle this issue.
In the blowroom it’s about managing trash reduction, and preventing the increase of short fiber content and neps. During cotton processing, the material is opened into tufts, with several stages of opening and cleaning aimed at removing impurities. But a side effect of these processes can be an increase in neps and short fiber content, due to the mechanical stresses. Some spinning mills adjust card settings or try to remove broken fibers during combing, but thorough testing and blowroom optimization are often considered more effective and economical approaches.
To control blowroom and carding performance, measurements with Uster AFIS are part of the routine test plan, and are also applied after machine maintenance or changes in cotton laydown recipes. These tests ensure optimal opening and cleaning at an appropriate waste level. Close monitoring of potential fiber damage is essential.
Processing statistics – track fiber characteristics
The processing charts in Uster Statistics track the fiber quality characteristics. Key parameters for neps, short fibers, and impurities are plotted through each processing stage. The accompanying graphic shows the typical increase in neps in the blowroom from bale to card mat, followed by a decrease after carding as neps are removed. Spinning mills can compare their own levels against the global standard, enabling a quick assessment of the situation, identifying areas of overperformance or potential improvements.
Various raw materials – one common goal
Process control is also important, and even more so when processing mechanically recycled cotton. Depending on the source of the recycled material and its opening method, the short fiber content might already be at a naturally higher level when entering the blowroom.
Similarly, fiber damage can apply to man-made fibers which initially have uniform cut lengths. Uster AFIS 6 is able to measure cotton as well as synthetic materials. With thorough quality management, spinners can identify fiber deterioration at source, before it results in yarn irregularity.
It is evident that fiber characteristics significantly affect both spinnability and yarn quality consistency. Therefore, understanding fiber quality and how fibers are treated during the spinning process is essential right from the start. Accurate measurement remains a fundamental requirement for effective control. However, this is only one element to be managed to avoid quality claims.
Uster combines technology and application expertise to support greater consistency in yarn production. The company’s know-how is freely shared in Uster News Bulletin No. 52, which includes more chapters offering ‘best practice’ advice – from spinners for spinners – on how to take control of quality claims. Additional application literature and the latest edition of Uster Statistics are available via the company’s digital platform.