Friction Stir Welding (FSW) tool consists of two main parts: a shoulder and a pin. The rotating shoulder, which is larger and concentric with the pin, generates frictional heat and applies pressure to soften the workpiece material. The pin, which is a protruding, threaded, or profiled cylindrical part, penetrates the material, stirs the softened metal to mix the components, and creates the weld joint.
Shoulder: The shoulder is the larger, outer part of the tool that rotates against the surface of the materials being joined. It creates most of the frictional heat that softens the material without melting it, and its diameter is calculated to pair with the thickness of the material to be welded. The shoulder confines the softened material and ensures a defect-free weld.
Pin: The pin is the smaller, protruding part of the tool that is plunged into the joint. The pin stirs the softened material, mixing it together to form the weld. Its geometry, often including grooves or flutes, helps facilitate this mixing and vertical material flow. It ensures that the materials are thoroughly combined and that the oxide layer is broken up to form a solid bond.