Are textiles only suitable for apparel? The textile industry has successfully countered received ideas like those over the past years and constantly driven new developments – and now it's time for pathbreaking developments in the tufting sector. Together with Groz-Beckert, the German Floor Coverings Research Institute (TFI) at the RWTH in Aachen has succeeded in manufacturing a textile stone floor via tufting. New future prospects for an entire branch of industry?
The invention of the tufting machine goes back to the idea of creating a highly productive yet simple method of using machines to create three-dimensional textile floor coverings.
The fundamental prerequisite for a fully-functioning tufting process is the use of high-elasticity yarns – and typical pile yarn types such as BCF or heatset yarns have precisely these characteristics. In the use of highly rigid or low-stretch yarn types, tufting has currently reached its limits, which is why the main application of the method is the production of textile floorings.
The manufacture of technical textiles – a very common occurrence in weaving or warp knitting – is only partially possible to implement with tufting. Even the production of artificial turf using PP/PE monofilaments exhausts the technological potential of tufting. But now all that has changed radically – thanks to a new development by the TFI, the Institute for Floor Coverings at the RWTH Aachen, in combination with tufting tools from Groz-Beckert.
To open up the field of applications in today's tufting to other technologies apart from textile flooring production, and as a service provider for testing, research and development, the TFI has tackled the challenge – with the support of various partners, including Groz-Beckert! In the course of several research projects, the yarn feed inside the tufting machine was analyzed, and an elementary problem here turned out to be the continuous delivery via the yarn feed rollers and the discontinuous need for yarn in the tufting zone.
Tufting tools need pile yarn on the basis of "two steps forward, one step back". This kind of feed cannot be provided by the yarn feed rollers, resulting in fluctuating differences in length between the tufting tools and the feed rollers. Typical pile yarns with high stretch can compensate for these differences in length without high thread pulling forces, but with low stretch yarns of the kind used in technical textiles, the differences in length cause extremely high peaks in the thread pulling force, as well as phases during which thread tensioning is suddenly reduced to zero. These situations occur at irregular intervals and cause faults in the finish. In the worst case, the entire tufting process can break down completely.
For a controlled and reproducible yarn feed within a tufting cycle, the movement of the yarn has to be modulated. Here, the TFI has developed an electronically controlled compensation element: the electric 'jerker', or 'E-Jerker' for short. This takes up the yarn from the yarn feed rollers continuously and passes it back toward the tufting zone with a predefined forward-and-back movement. The compensation movement is controlled by a servomotor and can be individually adjusted to suit the relevant yarn or tufting article.
Apart from the E-Jerker, which keeps yarn tension at the required level, processing of technical yarns also requires the right tufting tools. When tufting with a classic single-eye needle type, the yarns roll into the protective groove with every single downward movement. As the tufting process continues, this rolling movement creates a "twisted-wire" effect, which ultimately creates a blockage in the yarn ahead of the needle.
The consequence here is that the originally smooth yarn becomes irregular and uneven in places. Yarn movement – especially through the eye of the needle – becomes obstructed. Development of undesirable yarn twisting can be prevented by using Groz-Beckert tufting needles with advanced yarn feed. During the tufting process the additional yarn feed is always located above the level of the carrier, ensuring that when the carrier material is pierced, the yarn is always fed parallel to the needle. This solution – an additional yarn feed at the tufting needle – enables uninterrupted and reproducible processing of technical, non-elastic yarns.
With pile heights of more than 60 mm, artificial turf articles for stadiums and sports facilities represent the first technical products ever to be created via tufting technology. Feeding the monofilaments that are usually required for this is a major challenge for machine operators where constant and reproducible product quality is concerned. With today's machine technology, powerful vibrations in the yarn cannot be avoided. These vibrations result in thread breakage and an uncontrolled slippage at the yarn feed rollers – damaging the goods and lowering productivity at the same time. The first trials of the E-Jerker on tufting machines for artificial turf have shown that fluctuations in yarn tension can be greatly reduced, resulting in smooth feed of the pile yarns – for reduced error rates and a higher-quality end product!
Initial trials with Groz-Beckert tufting tools in the technical center at the TFI have shown that using the new approach, processing of non-elastic yarns on looping machines is now possible. Additional tests at Groz-Beckert – using specially adapted tufting tools for cut pile applications – have made it clear that cut goods can also be produced in an uninterrupted and reproducible manner.
Textile stone floors are one example here. Brittle basalt yarns, among others, have been processed – representative for yarns made from glass, carbon or highly abrasive metal fiber yarns. Further potential fields of application range from high-temperature insulation and electrically conductive textiles to filter materials and geotextiles for drainage, irrigation and slope stabilization.
Is there anything more you'd like to know about the new possibilities of tufting technology with E-Jerker? Then just get into contact with us.
The IGF project "Expanding the applications of tufting technology via use of an electronically controlled jerker bar" 16678 N / 1 by the research association Forschungskuratorium Textil e.V., Reinhardtstrasse 12 - 14, 10117 Berlin, was sponsored via the AiF as part of the program for promoting collaborative industrial research and development (IGF) by the Federal Ministry of Industry and Technology, on the basis of a resolution passed by the German Bundestag.