Although automation technology is developing rapidly, setup and control of nonwoven cards is still done manually and based on experience of the machine user. When the surrounding conditions change, process errors occur or the product is changed, the machine user changes the production parameters based on his experience. If process errors or changed conditions are not recognized fast enough, scrap is produced or the machine is stopped. In Germany, scrap production from the nonwovens industry in the value of €50 million is recycled every year.

Optical inspection systems for the detection of product errors like holes, stains and fiber lumps are available, but are only used rarely, as the use as a pure surveillance system is not economic. Most relevant use is the documentation of product errors for quality sensible nonwovens to prepare the following confection [DrS16]. An automated feedback of the measurement into the process is currently not available. Furthermore, it is not possible to measure the subjective quality like the machine user who is experiencing it. An approach using fuzzy logic was introduced [Tie11], but has never been realized in praxis.

In most cases, the measurement for automation technology in nonwoven cards is only used to control the drive speeds of the rollers. Closed loop controls are rare. Furthermore, the generated measurement data is mostly not stored. A systematic analysis of the data and modeling of the machine has never been done.

For these reasons the project “Easy Nonwoven 4.0“ was started by the Institute für Textiltech-nik Augsburg gGmbH (ITA Augsburg), a spin-off of the Institute für Textiltechnik der RWTH Aachen University. The two-year project started in June 2017 and is funded by the Bavarian ministry of economics and media, energy and technology. Besides the ITA Augsburg, the project consortium includes Dr. Schenk GmbH, Planegg, a supplier of optical inspection systems, iba AG, Fürth, a supplier of measurement and automation systems and the nonwoven producer Tenowo.

Within the project Dr. Schenk develops the optical inspection system to measure product errors (defects) and the subjective product quality like the machine user is experiencing it, during the production process. The iba AG is developing a measurement and automation system for nonwoven machinery that can be easily adapted for existing and new machines. The iba system saves the measurement data of the nonwoven machines and the optical inspection system and transmits the optimized setting values to the machine. The first demonstrators of the developed systems will be validated on the pilot line at Institut für Textiltechnik Augsburg. This way the components can be further developed without disturbing the production of a nonwoven producer.

ITA develops a cost/effort based setting aid and closed loop control for the most important drive speeds of the card. The setting aid takes not only the qualitative but also the economic impact of the settings into account. This prevents the optimization from choosing a setting point, where the product quality is optimised, but a production without profit is not possible. Basis of the setting aid is a modeling of the card to predict the quality at different settings and a detailed production cost model, that calculates the corresponding production cost. Closing an optimi-zation routine calculates the setting point, at which the desired product quality is produced at minimum cost.

Abbildung 1: Concept of the Easy Nonwoven 4.0 System
Beyond that, a closed loop control is developed, which adapts the roller speeds around the calculated setting point when the produced quality deviates from the desired quality. The closed loop control are based on extensive expert interviews and experiments, which are used to develop the control algorithms. The complete system shall adopt the parameters of the setting aid according to the actual produced optical web quality. Occurring product or process errors will be detected by the Easy Nonwoven 4.0 system and the roller speeds will be adapted accordingly.

The partial developments (optical inspection system, measurement and automation system, setting aid and closed loop control) will be implemented and refined at the pilot line at ITA Augsburg. Closing all partial developments will be validated in a production environment at Tenowo and compared to a benchmark production before implementing the systems.

The targeted impact of the project is to reduce the time needed for an article change by 20% and the scrap production by 50%. When implementing the system in all nonwoven lines this equals an additional production of approximately €25 million per year only in Germany, with a scrap production of approximately 5% before the implementation of the developments.

The authors thank the Bavarian ministry for economy and energy, media and technology for the funding of the project Easy Nonwoven 4.0.

Sources:
[Tie11] Tiedt, T.; Klietzing, T.; Raina, M.; Seide, G.; Gries, T.; Geus, H.-G.;Block, M.; Wüscht, M.
Kundenbezogene Qualitätssicherung in der Vliesherstellung
26. Hofer Vliesstofftage, Hof, 11.2011
[DrS16] Dr. Schenk GmbH (Hrsg.)
EasyInspect & Easy Measure – Automatische Prozess- und Qualitätskon-trolle für Vliesstoffe
Planegg, 07/2016
URL: http://www.drschenk.com/fileadmin/brochures/02-nonwoven_inspection/de/brochure_nonwovens_de.pdf
Letzter Zugriff: 15.09.2016