Development of FSW head for CNC machine tool: advantages, limitations and applications
By Gilles Sevestre (Stirweld), Laurent Dubourg (Stirweld)

The friction stir welding offers many advantages over conventional joining technologies, such as TIG, MIG or laser. Despite the development of robotic solutions for 10 years reducing the purchase cost of a FSW workstation, the investment cost remains an obstacle to the deployment of the process, especially in SMEs.

Stirweld has developed a FSW head that mounts on a numerical control machine tool (CNC machine) or a milling machine. Thus, a company or a laboratory having a CNC machine can perform FSW assemblies while limiting the investment cost. In addition, it is possible to complete a full manufacturing sequence on a single machine without workpiece displacement: part machining, FSW of these parts and then finishing operation. This development is particularly interesting for SMEs having small batches of pieces. Moreover, this is complementary to existing FSW machines, such as gantry type or robot, which are reserved for mass production.

The head presented in this work includes all functions required to carry out defect free welds while protecting CNC machine from FSW constraints. These functions are:
• Force control along the FSW tool axis. This control is performed directly into the head to not modify the command of CNC machine and to offer a universal solution to all CNC machines
• Cooling system in order to protect the CNC machine from the process temperature
• Protection against the high forces and vibrations during the FSW process to not damage the bearings of CNC machines
• Quick tool change from welding to machining to not move the workpiece between operations
• Recording of the forging force for quality control

The study figures out the advantages and limitations of FSW on CNC machines. Finally, the authors present six FSW applications performed on CNC machine:
• Frame of electronic device: assembly of different parts to reduce the raw material
• Aeronautics: welding of thin AA2024-T3 sheets
• Al profile: manufacturing of parts whose dimensions are not feasible in a single extrusion
• Liquid cooled heatsink: the objective for machining jobshop is to reduce the welding outsourcing cost
• Welding of dissimilar materials (Al / Fe) for application in industrial sheet metal.
• Copper connectors: replacement of hard brazing to minimize manufacturing defects