Uster: Ensuring consistent yarn quality in spinning
To help spinners, Uster experts have put together guidelines for avoiding yarn irregularity claims.
Producing consistent yarn quality is an everyday challenge – and a very difficult one. Detailed knowledge and understanding of the fibre raw material is absolutely 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.
Uster can say with greater certainty that the reasons for claims received by spinners have remained quite similar, at least in the past 20 to 30 years. Although the severity and distribution of the reasons may vary depending on the final use of the yarn, the most common factors can be identified. Analysing these factors and providing insights into the quest for operational excellence in spinning mills, the latest Uster News Bulletin No. 52 becomes a valuable tool to reduce yarn quality claims.
Laydown consistency – use data correctly
One factor which greatly impacts on the spinnability of cotton fibres, as well as the yarn quality, is fibre fineness. Cotton has inherent natural variations, so fibre fineness (micronaire) is therefore the most important parameter to be controlled within required limits.
Optimal bale mixing aims at a consistently narrow micronaire range. Minimising 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 fibre characteristics. This reduces manual work, but more importantly improves long-term quality from fibre to yarn by refining raw material selection.
Fibre 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 fibre 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 fibre content, due to the mechanical stresses. Some spinning mills adjust card settings or try to remove broken fibres during combing, but a more effective and economical solution is thorough testing and blowroom optimisation.
To control blowroom and carding performance, measurements with Uster AFIS are part of the routine test plan, as well as also being 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 fibre damage is essential.
Processing statistics – track fibre characteristics
Fibre processing Uster Statistics – Total nep count (/g)
The processing charts in Uster Statistics track the fibre quality characteristics. Key parameters for neps, short fibres, 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. This allows 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 fibre content might already be at a naturally higher level when entering the blowroom.
Similarly, fibre damage can apply to man-made fibres 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 fibre deterioration at source, before it results in yarn irregularity.
It’s clear that fibre characteristics significantly affect both spinnability and yarn quality consistency. Therefore, understanding fibre quality and how fibres are treated during the spinning process is essential right from the start. What is not measured, cannot be controlled! However, this is only one element to be managed to avoid quality claims.
Uster has the technology, the experience and the knowledge to foster a new level of 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.
About Uster Technologies
Uster Technologies is the world’s leading provider of quality management solutions from fibre to fabric. High-technology instruments, systems and services cover quality control, prediction, certification and optimisation. The portfolio comprises quality management, laboratory testing and in-line process control instruments for fibres, staple fibre, and filament yarns, fabrics and nonwovens.
Uster Statistics, the unique global benchmarks for textile trading, complement a portfolio of value-added services that includes training, consultancy and worldwide after-sales. The Uster philosophy aims to drive innovation forward by meeting market needs – always with ‘quality in mind’.
Uster Technologies is headquartered in Uster, Switzerland and operates worldwide. The company has a global network of 7 subsidiaries, with 50 sales agents and local service stations around the world.
