PTG has long used its knowledge of the FSW process to assist automotive OEMs in producing lightweight, robust and aesthetic components for battery electric vehicles (BEV) and plug-in hybrid electric vehicles (PHEV). Aimed at manufacturers of skateboard chassis structures, the dual weld head process developed by PTG ensures that a tight weld flatness tolerance is achieved during battery tray floor construction.

A tight weld flatness tolerance is essential to ensure that each battery cell sits perfectly level within its housing. PTG Powerstir dual weld head FSW machines provide an even and stable welding process, something achieved thanks to the company’s ‘matched’ dual-force control systems and balanced upper and lower head welding parameters. The result is stable FSW by both the upper and lower weld heads, producing matched weld seams with balanced heat input. This effect, in turn, minimises post-weld distortion and equips each welded assembly with an improved flatness tolerance when compared to existing conventional single-side FSW techniques.

As aluminium extrusion lines usually produce panels of 300 to 600 mm wide, PTG has also developed a fully automated, high-output Powerstir FSW production cell for the rapid friction stir welding of multiple extrusions, to create single structures for fabrication into battery tray floors. These structures are typically up to 2.4 m wide.

“Our dual weld-head FSW technologies, whereby both sides of an extrusion are welded simultaneously, not only remove the time-consuming process of lifting and turning extrusions between welds, but allow for equal heat dispersion, which results in minimal distortion,” says PTG Powerstir regional sales director Mark Curran.

In the PTG Powerstir dual weld-head FSW process, typically four to 12 individual child-part extrusions are brought together for assembly. Following gantry loading, each extrusion is automatically positioned and clamped ready for FSW, after which the partially completed vehicle component is automatically repositioned, ready for the next panel to be welded in place.

“In addition to providing automotive OEMs with a state-of-the-art means of joining metals and achieving extremely high-strength results, it is also important to consider that, in many instances, the use of FSW allows for reduced wall thickness – an important aspect in reducing vehicle weight,” says Curran. “As the FSW process generates very little heat, the crystalline structure of the metal remains unchanged, retaining its original strength. There is no need for inert gas, no need for heat-treating post weld, and no requirement for additional surface finishing.

“In addition to building Powerstir machines specifically for the production of battery tray floor assemblies, we are also creating FSW techniques for the production of coolant units, control box panels and car body panels, as well as body panels and components for commercial vehicles,” adds Curran.