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Friction stir welding of 3D-structures and flexible components

: Grimm, Andreas

Welding Institute -TWI-, Cambridge:
9th International Symposium on Friction Stir Welding 2012 : Held 15 - 17 May 2012, Huntsville, Alabama, USA
Red Hook, NY: Curran, 2013
ISBN: 978-1-62276-608-6
International Symposium on Friction Stir Welding (ISFSW) <9, 2012, Huntsville/Ala.>
Fraunhofer IWS ()
Reibrührschweißen; Geometrische Form; dreidimensionale Struktur; parallelkinematische Maschine (PKM)

The aim of the present work was to identify and verify a new machine concept for friction stir welding. In the long-run this should help to offer new opportunites for using this metallurgically superior and energy-efficient solid-state process in a wider range of industrial applications. In a first step, parallel-kinematic systems were chosen as a suitable alternative to common systems due to their simple setup and advantages in relation to stiffness and positioning error. A Pentapod, a five axis based parallel-kinematic system was identified in a second step as the best candidate to achieve the goal of a cost effective and precise machine with a good space/working space ratio. Its kinematic is mainly based on the well known Hexapod-concept: But by leaving out one of the six actuators and adding a rotary table, the space/working space ratio of this fully 3D-capable machine is significantly increased. To enlarge the work space further, the parallel-kinematic system was coupled to an additional drive set. Control mechanisms are very important for achieving reproducible high quality friction stir welding results. During the project the system was successfully equipped with the necessary control modes: force, torque and position control. By using mainly internal sensors, reliable and stable control algorithms have been implemented and verified. Only position control is operating with an additional external sensor. Since test results showed that its resolution is not fully satisfactory, this control mode will be revised in the near future. Welding trials have been carried out successfully to investigate the capability of the Pentapod-system for friction stir welding. Welding of slack components as well as curved 3Dstructures of light weight alloys have proven the capability of the system. Examples of additional mixed material studies of copper and aluminium are also presented. At the end of the project a fully 3D-capable friction stir welding machine centre with a maximum payload of 12.0 kN and a working space of 6.5×2.0×1.5 m3 has been established.