Thermo-rheological optimization of additive manufactured extrusion dies

• Applicants: Professor Dr.-Ing. Reinhard Schiffers; Professor Dr.-Ing. Gerd Witt
• Subject Area: Plastics Engineering ; Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 329847022

In the design of extrusion dies, proven geometries such as spiral mandrel distributors have been used for years for blown film extrusion. The design, especially for complex variants, is also dependent on production-related restrictions. In addition to the temperature balance, the flows close to the wall, which are defined as such immediately after entry into the spiral mandrel and thus significantly characterize the residence time spectrum of such a die, are also problematic. With today's possibilities of additive manufacturing technology (AM) there is potential for the thermorheological optimization of the melt channels. The extension of the geometric degrees of freedom compared to conventional manufacturing processes allows structures and channel shapes which have a positive influence on the flow behaviour and thus can increase the tool performance. The surface qualities of the melt-conducting channels in particular pose a great challenge in terms of production technology, so that there is a need for a suitable post-treatment chain. Within the framework of the preliminary project, a demonstrator tool was presented which was designed on the basis of numerical flow simulations and manufactured completely additive. The primary objective of the design was to achieve a homogenization of the temperature distribution within theplastic melt by means of radial mixing elements and to significantly reduce the residence time spectrum at the outlet of the tool in order to reduce purging times. For an adequate product quality, this must be achieved without negative influences from any weld lines. The demonstrator tool, which was developed within the scope of the first project and tested in initial test series, was able to provide initial evidence of an increase in performance.The knowledge gained, however, indicates the need to continue the research project with the aim of extending the simulation methods and gaining a deeper understanding of the interactions of the manufacturing process chain, the resulting component properties and the performance in the extrusion process.

• DFG Programme: Research Grants