Friction stir welding represents a novel approach to the joining of two workpieces, whereby frictional heating and mechanical mixing of their surfaces facilitate the formation of a solid connection without melting. This method is particularly noteworthy for its ability to create strong, pore-free welds with a small heat-affected zone and minimal distortion, rendering it ideal for demanding applications in the aerospace and automotive industries. The application of friction stir welding to high-strength aluminum alloys is particularly advantageous due to its excellent processability and effective prevention of weaknesses such as porosity and melt defects.
Building on this technology, the Material Testing Institute (MPA) University of Stuttgart has developed a new additive process based on friction stir welding, incorporating material feed to address minor gaps in the joining zone and fabricate components by adding filler material. This novel method is distinguished by its capacity to produce high-strength aluminium alloy structures, a feat that is particularly challenging to achieve with other additive manufacturing techniques.
The innovative tool for this process features an extruder screw with a pin on the underside, similar to those used in traditional friction stir welding. The extruder screw is encased in a tool shoulder that channels the plasticised filler material. The preliminary trials have produced encouraging outcomes, with the provided wire being accurately divided into uniform sections and successfully incorporated into the welding procedure. This success has enabled the initial deposit welding operations and the construction of a small-scale structure.
Presently, the system is being developed to be adaptable to a HSK 63 tool holder, which will facilitate seamless integration with existing machining apparatus and enhance its versatility and potential for utilisation.