Automated simulation-driven analysis of lightweight design strategies for the efficient design of film extrusion dies – optimisation of both die mass and flow path length and reduction of thermal setup time

• Applicant: Professor Dr.-Ing. Christian Hopmann
• Subject Area: Plastics Engineering
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 518072893

Extrusion dies are used to continuously form complex products such as a co-extruded film spanning several meters in width. The combination of high pressures due to high viscosity, multiplicity of flow channels in a co-extrusion die and the large product width means that high mechanical loads act on the extrusion tools. To ensure that the individual die plates remain sealed against each other despite these loads, the die plates are sized conservatively, i.e. sized to be very voluminous and thus very rigid. In turn, the large volume or the resulting large masses leads to difficulties in handling, long flow paths and long thermal setup times. Thermal setup times occur when waiting for the die to heat up or cool down when changing to a new product. It is - as of today - not known to what extent a deviation from the conservative sizing for extrusion dies of different types and dimensions is a) possible and b) beneficial. The research project applied for therefore creates essential basic knowledge. It does that by investigating different lightweight design strategies using simulation. In the research project applied for, different simulation-driven lightweight design strategies are therefore investigated. The aim is to find out - depending on the size and type of extrusion die - which lightweight design strategies lead to lower masses, reduced flow paths and shorter heating times. In order to achieve this goal, however, a simulation environment must first be created that can accurately capture the interactions that occur between strongly geometry-dependent flow in the flow channel and flow-dependent deflection of the die plates. In addition, this simulation environment must allow the geometry of the tool plates to be automatically adjusted. Both challenges can be met by using the immersed-boundary-surface method, which has hardly been established in plastics processing so far. First, this method will be validated by means of a comparison with conventional calculation methods and laboratory tests with a particularly flexible tool made from PMMA. Afterwards, the following lightweight design strategies are applied automatically: substitution of steel by aluminium, stiffening by curvature, highly precise mechanical design, ribbing as well as topology optimization. Two fundamentally different designs of extrusion dies and seven different die sizes between 300 and 5000 mm in outlet width are investigated. The simulated improvements regarding tool mass, flow path length and heating time are analyzed in detail and compared to industrial dies. With this data, a majority of the extrusion dies can be evaluated with regard to the potentials of lightweight design for the first time. Two optimized dies are manufactured and examined in extrusion tests, so that - in addition to the calculation method - the optimization method can be validated.

• DFG Programme: Research Grants