Faster Virtual Spinning Thanks to Simulation

Project VISPI: Validation of a Simulation Tool for Virtual Spinning

In the VISPI project, we are working together to develop simulation software that can be used to virtually map and investigate a wide range of spinning processes. The project is funded by the Federal Ministry of Education and Research (BMBF).

It is one of the oldest techniques of mankind: spinning. However, classic spinning mills that process fibers into yarn can hardly be found in Europe anymore – the majority of man-made fibers are produced in China these days. Globalization also affects the production of synthetic fibers. German fiber manufacturers are therefore focusing on »new developments with high added value«: the aim is to distinguish themselves from the mass-produced goods in Asia and still hold their own internationally. We support this vision and are developing simulation software that virtually simulates and analyses a wide range of spinning processes.

Mechanical engineering, which is part of this industry segment, is still strongly rooted in Germany. Industrial research into product and process innovation is reaching its limits on a purely experimental basis. The solution: virtual simulations.

Digital Twin Optimizes Spinning Process

Simulations save experiments, allow new insights, enable systematic parameter variations and solve upscaling problems that can lead to serious misinvestments in the transition from laboratory to industrial plant. However, the simulation of spinning processes is quite complex because very different steps are performed in quick succession. The required simulation capability for spinning processes is therefore currently limited to research institutions, whereby we as the Fraunhofer ITWM also play a leading role in a worldwide comparison.

The LSP Chair of Polymer Materials of the Institute of Materials Science of the Friedrich-Alexander-Universität Erlangen-Nürnberg contributes outstanding know-how in polymer physics and materials science. Together with the LSP Erlangen, it is important to provide the appropriate simulation tools and capabilities directly to the developing companies as quickly as possible. After all, the provision of appropriate simulation tools can make a significant contribution to maintaining the competitiveness of fiber manufacturers and mechanical engineering companies in the future.

The fibers are pressed through these spinning nozzles. The nozzles are located at the upper end of the spinning shaft of the plant at the project partner LSP Erlangen.
© Fraunhofer ITWM
The fibers are pressed through these spinning nozzles. The nozzles are located at the upper end of the spinning shaft of the plant at the project partner LSP Erlangen.
Scheme Virtual Spinning
© Fraunhofer ITWM
Scheme Virtual Spinning

The Process: Spinning Synthetic Fibers

In spinning processes for the production of synthetic fibers, molten or dissolved spinning mass is pressed through fine nozzles, spun into fibers and then guided through a cold air flow or a spinning bath for curing. Known processes are melt spinning, solution spinning, gel spinning and dispersion spinning.

The following graphic illustrates which simulation concepts are required for the simulation of spinning processes using the example of melt spinning.

In recent years, our experts have developed a simulation tool focus on the specific use cases of industry: VISPI (Virtual Spinning).

The Software for Virtual Spinning: Many Parameters and Database With Polymers

The graphical interface of the tool allows users to enter all required boundary conditions, including positions and diameters of the nozzles in the spin pack.

The following specifications can also be made:

  • the mass flow or the spraying speed
  • the temperature of the polymer fibre is specified
  • the density
  • the specific heat capacity
  • the viscosity
VISPI – Die Software zum virtuellen Spinnen
© Fraunhofer ITWM
VISPI – Die Oberfläche der Software zum virtuellen Spinnen.

A material database with common polymers is also integrated in VISPI. The tool reliably maps the spinning process virtually, which makes it possible to examine both the flow-dynamic design of the spinning duct and the arrangement of the filaments in the spin pack. In the spinning duct, the air is heated by the filaments and entrained downwards. In the process, the rear rows are not cooled as effectively as the filaments that are close to the blow-off. This is reflected in different material properties in the final product.

Gruppenbild beim Kick-off-Meeting
© Fraunhofer ITWM
Gruppenbild beim Kick-off-Meeting des Projektes am 17. September 2019 im Fraunhofer ITWM.

Simulating in Cooperation

We focus on the development of mathematical numerical methods for simulation, while the University of Erlangen contributes its expertise in polymer physics to the development of a material database.

Our institute has developed physical models and mathematical algorithms for the simulation of spinning processes in fundamental research projects. Using the production of glass wool and several polymer spinning processes as examples, we have demonstrated that simulations both improve fibre product properties and reduce energy costs.

Test Runs on Fiber Spinning Plant at FAU Erlangen-Nuremberg

Initial tests of the software were promising – for example, on the fiber spinning plant of the LSP Chair of Polymer Materials at the Friedrich-Alexander University Erlangen-Nuremberg, the project's partner. This brings the researchers a big step closer to their goal: to develop mathematical algorithms into licensable simulation software.


Target Achieved, Perspective and Duration of the Project VISPI

The aim of the project was to develop the simulation tool »Virtual Spinning (VISPI)«, which maps, designs and optimizes innovative industrial spinning processes for high-tech fibers. The software was tested by different institutions and the feedback from the testers was very positive.

The VISPI project ran from July 2019 to June 2022 and was successfully supported by the BMBF funding measure »Validation of the technological and societal innovation potential of scientific research«.