More than just benchmarks – practical quality benefits for all to see...

How USTER® STATISTICS can be applied to eradicate common fabric defects such as pilling and uneven appearance

Uster, Switzerland – 15th May 2013 – Everybody knows USTER® STATISTICS – the globally-established benchmarks for the textile industry. But how are they used in practice, and how do they influence the fabrics and garments we all wear every day? To put it another way, what would textiles be like without USTER® STATISTICS?

For the answers, it might be useful to start with an example (Figure 1) of a particularly troublesome fabric defect that we are all familiar with: pilling (sometimes called 'bobbling') – the appearance of little balls of fuzzy fiber on the surface of a garment. Obviously, pilling is a serious problem for the entire production chain, since the consumer's dissatisfaction with a product will quickly rebound on the retailer, clothing manufacturer, fabric producer and, ultimately, the yarn spinner.

Figure 1: Pilling effect in a fabric caused by a high hairiness value

Pilling: causes and prevention
When we look at an example of pilling, there is a simple statement we can make: “With USTER® STATISTICS, this wouldn't have happened.” In most cases, fabric defects can be traced back to the yarn – not necessarily 'bad' yarn, but usually yarn with the wrong quality specification for its intended end-use. With pilling, the cause is generally a yarn which is too hairy. To define the level of hairiness – the H value – in a yarn spinners carry out a routine in their lab, testing the yarn package.

The numerical H value resulting from the test is automatically matched against percentile levels in USTER® STATISTICS. These percentiles, known as USPs, show by how much the yarn is above or below a certain value, based on comparisons with what other spinning mills worldwide are producing. For example, the 5% level means 5% of mills worldwide are producing yarn with equal or better quality levels for the particular parameter being compared. The same applies to the limit levels of 25%, 50%, 75% and 95% shown up by the USTER® STATISTICS.

In the fabric example illustrated here, the level of pilling was produced by a yarn with an H value of 7.71, equivalent to a USP of 95% – clearly showing that the yarn hairiness was too high for the end-use. To avoid pilling, a fabric specialist would be able to determine that, in this case, a yarn with hairiness USP of 50% would have been required.

Uneven fabric appearance: a clear view
A second example (Figure 2) shows another kind of defect which can also lead to lost customers: uneven fabric appearance with very visible faults and inconsistencies that are always going to be unacceptable. This type of defect has a number of likely causes, all showing up in the yarn: too many neps in the raw material; too many short fibers in the yarn; poorly-maintained machinery; etc.

Figure 2: Uneven fabric appearance due to inconsistent yarn quality

And, once again, we can confidently say: “With USTER® STATISTICS, this wouldn't have happened.” To eradicate the kind of unsatisfactory uneven fabric appearance seen in this example, we must focus on the yarn quality parameter known as CVm, for Coefficient of Variation of mass. Experience has proved that this characteristic strongly impacts on how we can expect the finished fabric to look.

Here also, the USTER® TESTER 5, the Yarn Inspection System provides the vital test data. And here again, the correlation with USTER® STATISTICS percentiles is critical to understanding and controlling the yarn properties to ensure a satisfactory fabric appearance. For most fabrics, a 50% USPTM level for CVm is likely to give an acceptable result, while in our example, the measured CVm value of 13.9 translates into a USPTM of 80% – explaining why the fabric obviously does not make the grade in terms of appearance.

USTER® STATISTICS: interesting insights 
The examples given here underline the real and practical advantages USTER® STATISTICS bring to the textile industry. The basis for these benefits is a substantial and extensive project – running over five or six years – to prepare each edition of USTER® STATISTICS. It involves the thorough collection and testing of several thousand samples, carefully targeted to be representative of worldwide textile production capacities. The results are fed into unique data analysis software for interpretation and calculation of the percentile curves. Finally, the USTER® STATISTICS are issued in the form of powerful interactive software, accessed via the internet or on CD.

USTER® STATISTICS – a powerful and practical quality resource, freely available for all, helping the textile industry to deal with pilling and uneven fabric appearance – and much more besides.