The Project

FlexiFab aims to create an automated robotic system to enable welding of aluminium components.

The system will use friction stir welding technology (FSW).The welding method offers a number of benefits for aluminium joining/welding such as:

  • A mechanised repeatable process.
  • No special pre-weld edge profiling or cleaning required.
  • No shielding gas required.
  • Low distortion and shrinkage due to solid-state nature of welding process.
  • Welding in any position.
  • Excellent weld mechanical properties.
  • High efficiency processing with very low energy consumption.
  • Ability to weld the ‘non-weldable’ aluminium alloys such as the 2000 and 7000 series
Operator Health & Safety benefits:
  • No harmful welding fumes or hot metal spatter.
  • No UV radiation hazards


The FlexiFab system will provide the following key competitive advantages to the European welding Industry

  • Enable European fabricators, metal-workers and welding companies to effectively compete in the growing use of aluminium alloys in the light-weight transport sector.
  • Reduce the costs associated with the fabrication of aluminium structures, especially focussed on components used within the transport sectors.
  • Capitalising on the increasing pressure to replace traditional iron and steel material with aluminium alloys to reduce weight and thus fuel consumption of vehicles, trains, ships/boats and aeroplanes.
Project aims
Schematic of the FlexiFab System

Welding Techniques


Fixed Bobbin FSW


 Fixed bobbin FSW tools, unlike conventional FSW tools, have two shoulders running on both the top and bottom of the work-piece. This tool design reduces the welding forces on the work-piece and FSW machine during processing, eliminates ‘kissing bonds’ and the requirement for a rigid backing support and fixturing.

The floating-bobbin FSW technique uses a fixed bobbin tool held in a sleeve which allows it to float in the Z axis. The fixed bobbin tool therefore moves to balance the force on each of the shoulders to automatically find the position of least resistance during welding, resulting in dramatically reduced process forces.

Stationary Shoulder FSW

With the Stationary Shoulder FSW technique, only the probe is rotating and generating frictional heat, while the non-rotating shoulder is sliding over the material surface. The force applied on the shoulder guarantees a sufficient forging force inside the weld, resulting in a high quality solid state joint. The benefits, compared to conventional FSW is a smaller heat affected zone, superior surface quality and reduced sensitivity for robot deflections. The video below shows an example of a three-dimensional strucure, welded by robotic stationary shoulder FSW. 

Corner FSW

The stationary shoulder FSW technique has been further developed, whereby the shoulder is shaped to fit the component geometry. This opens up a whole new range of applications for SSFSW, including tailor welded blanks and T-joints. Within FlexiFab, Corner welding of T-joints has been developed for 3mm thickness AA6082-T6, AA5053-H111, AA2024-T3 and AA7075-T6.

Corner FSW for these alloys has been successfully demonstrated on the FlexiFab robot system.