Fraunhofer Institute for Industrial Mathematics ITWM
Fraunhofer Institute for Industrial Mathematics ITWM
Design von Spinnpaketen optimieren
© DITF / Fraunhofer ITWM
Design von Spinnpaketen optimieren

© DITF / Fraunhofer ITWM

Designing Polymer Spin Packs

Optimize the Design of Spin Packages Using a Digital Twin

Our software solutions simulate spin packs as a digital twin to understand the flow behavior inside and to optimize the design. 

Spin packs are used in the production of synthetic fibers and nonwovens. The spin pack itself is a metal block and consists of cavities and fine channels inside, through which polymer melt – i.e. molten plastic – flows. This melt is fed into the spin pack through a tube. In a first cavity, the melt is distributed over the entire width of the spin pack. It passes through several layers of filters held by a support before being spun into fibers by fine capillaries in the spinneret plate.. This produces fibers that are either wound into a yarn or laid down to form a nonwoven fabric.

Analyzing and Simulating – A Look Inside the Spin Packs

Our work always starts with a flow analysis of a given design. Our team simulates the flow in the spin pack, taking into account the flow behavior of polymers. With the aid of our software tools, residence times and pressure curves are then evaluated.

The analysis provides targeted information on which components of the spin pack should be optimized. Often, significantly increased residence times occur in cavities. This is unfavorable because the polymer degrades after some time under the temperature load. To prevent this, our experts use shape optimization to design components with low and uniform residence times. In the same way, strong pressure generators become visible through the analysis and the corresponding components can be adapted.

Flow Paths Through a Typical Spin Pack
© Fraunhofer ITWM
Flow Paths Through a Typical Spin Pack

This simulation-based analysis provides a view into the spin pack that would otherwise remain hidden. Since detailed measurements of the polymer flow in the spin pack are not possible, problems in the spinning process can so far only be addressed by trial-and-error. This is the advantage of simulation-based design, because all fluid dynamic quantities can be measured quantified. Problematic components can be identified and modifications are immediately validated. Development times become shorter and companies avoid expensive faulty designs.

Automated Cavity Design Avoids Dead Zones and Polymer Degradation

Dead zones within the spin pack or stagnation zones with slow flow velocity can have an extremely negative impact on product quality and overall spin pack performance. Since the residence time in these areas is high, polymer degradation can occur. Degraded polymer can enter or block the fine capillaries. This can eventually lead to filament breaks, frequent cleaning cycles and production stops.

Reference-Spin-Pack-Design
© Fraunhofer ITWM
The reference design of the spin pack has a stagnation zone with a large residence time, where polymer degradation can occur. We have optimized the shape of the polymer distributor and the zone has disappeared.
Analysis of residence time for different designs of spin packs.
© Fraunhofer ITWM
Analysis of residence time for different designs of spin packs.

Our flow simulations are a reliable tool to identify this dead zone and areas with very slow flow velocities. The remedy is then to change or redesign the spin pack geometry. The optimal geometry can be complex. Therefore, we have developed automated design tools for spin pack geometries.

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