Friction Stir Welding Machine Product

Overview

Friction stir welding (FSW) is a solid-state joining process ideally suited to aluminum and other nonferrous alloys. Unlike arc welding or fusion processes, FSW uses no melting and produces no porosity or hot-cracking problems. Instead, a rotating tool with a special shoulder and pin is plunged into the joint between two abutted plates, heating the metal via friction. The rotating pin stirs the softened metal, intermixing the two sides and creating a strong weld throughout the depth.

The process was invented in 1991 in the UK and has become standard in aerospace, automotive, and marine industries for joining aluminum airframes, boat hulls, and rail car bodies. An FSW machine is essentially a precision CNC mill adapted for the unique demands of friction stir welding: high rotating speeds (500–2000 rpm), massive downward forces (10–100 kN), and precision vertical position control (±0.1 mm).

The High-Speed Spindle holds and rotates the FSW Tool Assembly. The Force Control System system applies and maintains the plunge force. The Gantry & Bed Structure is a rigid CNC portal moving the tool along the weld seam. The Work Holding & Clamping system holds the workpiece against a Backing Bar. The Controller & CNC orchestrates the entire sequence.

How it works

Two aluminum plates (or other metals suitable for FSW—copper, magnesium, titanium alloys, even some steels) are positioned edge-to-edge, abutting along a line. The joint faces should be clean and flat. The workpieces are clamped to a table or backing bar using the Work Holding & Clamping system, securing them rigidly to prevent relative motion during the weld.

The High-Speed Spindle is spinning at a preset speed—typically 1000–1500 rpm for aluminum, depending on plate thickness and alloy. The Controller & CNC executes a preprogrammed sequence. First, the gantry moves the spindle to the starting end of the joint. The Force Control System system begins lowering the spinning FSW Tool Assembly, bringing the tool's Shoulder (the large flat surface) into contact with the top of the workpiece.

As the shoulder comes into contact and friction begins, heat is generated. The spinning pin penetrates the joint, entering the abutting faces. The Servo Vertical Actuator continues pressing downward at a controlled rate, until the Load Cell reaches the target plunge force (20–50 kN typical for 6 mm aluminum plate). Once the target force is achieved, the servo loop maintains it constant throughout the weld.

With the tool fully plunged, the Gantry & Bed Structure begins moving the spindle along the joint line at a slow welding speed (50–300 mm/min). The rotating shoulder continues generating heat via friction, keeping the metal in and around the pin at a plastic state (typically 200–400 °C for aluminum). The Pin penetrates the full depth of the joint and rotates, stirring the two sides together.

As the tool travels, it mechanically intermixes the metal from the advancing side (the direction of tool travel) and retreating side. The metal behind the tool (in the wake) cools and solidifies. The final weld is devoid of porosity, with mechanical properties matching or exceeding the base material—quite different from fusion welds, which often weaken at the heat-affected zone.

The Backing Bar below the joint absorbs heat and prevents metal from squeezing out the bottom. As the tool reaches the end of the joint, the plunge force is gradually reduced, and the spindle retracts. The Cooling System has been circulating coolant through the Coolant Pump throughout the weld, keeping the Bearing Cartridge and tool holder at operating temperature (< 60 °C), since excessive thermal growth would throw the tool out of alignment.

The Temperature Sensor monitors the workpiece surface temperature near the tool; if it rises above a threshold (typically 450–500 °C), the controller may reduce the spindle speed or tool travel speed to prevent excessive heating and metal softening. The Torque Sensor on the spindle measures the reaction torque from the pin stirring the metal; an unexpected jump in torque might indicate a defect or tool wear.

After welding, the part cools in air (or is cooled by water spray), and the clamping is released. The weld exhibits a distinctive surface: a series of transverse grooves left by the rotating shoulder, and a fine-grained, equiaxed microstructure inside. Mechanical testing shows the weld zone strength is often 90–100% of the base metal.

FSW excels at joining:

• Aluminum airframe panels and stringers (Boeing 777, 787)
• Marine hulls and tanks
• Rail and automotive body components
• Thick plates where porosity is a concern

The lack of melting also means no need for filler wire, no oxidation of the weld, and minimal distortion or residual stress. The process is repeatable and scalable to very large structures via traveling portal frames like those used in aerospace assembly lines.