Making sure the length is right: contact-free measurement of textile webs

Producing standardized soiling on a wide variety of textiles and at the highest standard – this is the process the company Swissatest Testmaterialien AG in St. Gallen in Switzerland has mastered. The textile test strips – treated with samples of animal blood, wine, cocoa, soot and skin oil – are used to test and determine the efficiency of detergents and washing machines. Using the SPEETEC laser surface motion sensor from SICK for non-contact length measurement, Swissatest ensures the contact-sensitive test strips can be tested for defects and cut to length in a user-friendly manner during the manufacturing process.

“Several aspects speak in favor of using SPEETEC as a sensor for length measurement,” explains Harald Klien, Head of Technical Projects at Swissatest. “Firstly, the non-contact measurement leaves no traces on the soiled textile strips and, in contrast to rubber wheel measurement systems, also no abrasion marks. Secondly, when visually inspecting the tex-tile web we can move it forward and backward in the machine without a changeover – which was not possible with the previously used class 3 laser sensor.

Furthermore, there is the enormous cost-effectiveness of the sensor – not only on account of its sensible, affordable price, but also due to its low laser class 1 rating, which means we no longer need to implement additional safety measures on the machine.” When, during pre-liminary testing of the SPEETEC, the experienced textile technologist also obtained good results for the measurement accuracy and reliable functioning of the device independent of the materials and soiling media, they decided in favor of the speed and length measurement sensor from SICK.

SPEETEC: new solution for a known challenge

SPEETEC is indeed the ideal solution when it comes to performing automated speed, length, and position measurements for extremely smooth materials with a tendency to slip, for sensitive surfaces such as the textile test strips from Swissatest, or for materials prone to abrasion or adhesion. “This challenge has existed for a long time – and the textile industry has been waiting just as long for a sensor solution like SPEETEC,” says Harald Klien and adds: “Especially since the sensor operates with micrometer precision, even for acceleration measurements, in start-stop applications with short material lengths as well as, which is especially important to us, in the forward-backward mode of a roll winding machine.”

Defined soiling: more than “just” contamination

The present Swissatest Testmaterialien AG has been producing soiling on a wide variety of materials since 1962 and can call itself the market leader with hundreds of thousands of test strips per year as well as around 1,500 large-sized customers around the world in almost 100 countries. “This is also evident in the quality – because the valid testing of detergents, washing machines and dryers, the assessment of washing, cleaning and hygiene systems, or the preparation of appropriate expert opinions by Swissatest requires that all soiled test strips – as a quasi standard – possess long-term consistent quality characteristics.

They have to fulfill a number of relevant standards in order, in the end, to ensure comparable results and enable the differences between machines, cleaning agents and processes to be assessed,” explains Harald Klien. After dying, the textile webs that were previously soiled with pigs blood, red wine, cocoa milk, soot containing machine oil or skin oil are first dried, then measured colorimetrically and subjected to a visual product inspection prior to being wound up on a roll winding machine. Finally, the soiled textile webs are cut to a defined length and rolled up – as supplied to the customer or trimmed and sewed together into test strips in the manufacturing department of Swissatest.

SPEETEC greatly simplifies visual inspection for staff

For Harald Klien, SPEETEC offers the right price and precision. He particularly emphasizes that the “the process of visually detecting defects in the textile has been significantly simplified using the sensor from SICK.” It is necessary for the inspection staff to be able to arbitrarily move the textile web forwards and backwards in the roll winding machine without a changeover in order to precisely localize defects.

“In contrast to the laser velocimeter we used previously, which could not easily measure a forward and backward movement, the SPEETEC does not care in which direction the measurement is being taken, how much the material tension changes during measurement and wind-up, or how often a reversal of direction occurs in the inspection process,” which is a further clear advantage of the innovative surface motion sensor confirms Harald Klien. “This has significantly simplified the visual inspection task.”

The SPEETEC impresses – not only at Swissatest – with its non-contact, slip-free and high precision measurement principle, its ease of integration, and its exceptional cost-effectiveness. It therefore represents a new generation of laser sensors for measuring linear movements of surfaces – for applications well beyond the textile industry.

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