Fine-tuning friction stir welding

Temperature control: Heat sensor welding

Swedish engineering researchers have developed a robotic welding method that improves the controllability of the friction stir welding process.

In friction stir welding, a rotating non-consumable cylinder is pressed into the material to be welded. The combination of frictional heat and the mechanical “stirring” creates a high-quality welding joint without melting the material.

However, it can sometimes result in the metals reaching melting point and the welding tool sinking through the sheets. For accurate welds, both the process forces and the temperature must be properly controlled. 

Researchers at University West in Trollhättan have invented a welding tool that also functions as a sensor to measure temperature continuously. The heat is regulated by controlling the force and tool rotation. An industrial robot performs the welds to achieve a constant quality.

The university’s Jeroen De Backer said: “It’s thanks to this temperature controller that we’ve managed to raise the quality and productivity of the robot system. The robot welds with higher precision and with the temperature controller it only takes a few hours to programme 3D joints. Manual programming of a similar component took up to a week.”

The research project was a collaboration between Volvo Aero, Saab Automobile and the welding equipment company ESAB. 

De Backer said that one application could be in the manufacture of hybrid and electric vehicles: “Car manufacturers aim to reduce the weight of the electric vehicle and positioning of the heavy batteries is a key factor in this. 

“The battery consists of different metals such as aluminium and copper. Friction stir welding provides the possibility to join those materials and allows thereby integration of the battery in the vehicle chassis so that the battery becomes a part of the bearing structure.”