Colloquia

Summary

The use of additive manufacturing (AM) in producing lightweight aluminium products for industries such as aerospace and automotive holds great promise. However, the AM techniques employed often involve melting the feedstock material into the liquid state, which introduces several metallurgical challenges. Therefore, adopting a solid-state (SS) AM approach, where the feedstock material remains below the melting temperature, may provide a viable solution.

At the Production Technology chair, a new SS AM process for aluminium alloys has been developed, known as Friction Screw Extrusion Additive Manufacturing (FSEAM). In the FSEAM process, the feedstock material is forced against an extrusion screw that transports and bonds the material onto a substrate at temperatures below the melting point. It results in a fine-grained microstructure with in general good mechanical properties and without porosity. Currently, the feedstock material is supplied using a hydraulic cylinder. However, the limited stroke of the cylinder prevents continuous feeding of the feedstock material, leading to undesirable temperature fluctuations within the system, which may affect the resulting material properties of the fabricated parts.

Therefore, a continuous feeding mechanism for feedstock material was developed in this master work to further improve the quality of the FSEAM process. First, models were developed to predict the maximum force possible to load the feedstock material into the FSEAM system using both elastic and plastic rolling of the feedstock material. It became evident that some degree of plasticity was necessary to meet the required load force. Then, an experimental setup was developed to substantiate the findings of the model. The experimental results showed good agreement with the forces predicted by the model, demonstrating the feasibility of using plastic rolling as a suitable mechanism for continuous feeding of the feedstock material into the FSEAM system.

Subsequently, a detailed design of a feeding mechanism was developed based on a pair of rolling wheels employing some degree of plastic deformation, that was integrated with the existing FSEAM setup and which was in line with the findings of the experiments.