Lightweight Construction for the Automotive Industry with Friction Stir Welding

Welding of Mixed Joints

For the production of battery trays for electric vehicles, six FSW gantry machines from Grenzebach are already in use at the plant in Brežice near the Croatian border. The battery trays are manufactured from various individual parts made of two different aluminum alloys. Four cover plates and nine extruded sections are welded together to form a battery tray.

Aluminum is considered to be difficult or impossible to fusion weld, partly because of the aluminum oxide layer. As a pressure welding process, friction stir welding is superior to other fusion welding processes when processing aluminum alloys and mixed joints because the components are not fused at the seam but stirred together. Although the seam is heated, it is joined in a solid state.

"In addition to the high weld seam quality, the speed of the process steps is of course crucial in series production. Grenzebach's technology completely convinced us on these two important criteria," says Emir Šoštarec, Supply Chain Manager at TPV Automotive.

Friction Stir Welding: a Fast yet Robust Process Step

Grenzebach's four-axis gantry systems ensure absolute process reliability throughout the entire work area. The gantry system is designed for high axis dynamics and precise web guiding - embedded in the HYDROPOL® machine bed, which is specially designed for very high stiffness, low dynamic compliance and deformation. Due to the high welding depth, TPV Automotive uses the conventional tool with rotating shoulder. This is a fast yet robust process that delivers reliable and reproducible weld quality across the entire work area. "The battery trays must be welded one hundred percent tight so that no liquid can escape in the event of damage to the battery," explains Emir Šoštarec.

Welds: Extremely Strong - and Low Distortion

Friction stir welding can play to its strengths here. A rotating tool generates the required process heat through friction and pressure at the seam. The material is plastically deformed by the applied heat and stirred along the seam by the rotation of the tool. The seam created in this way is characterized by particular tightness. Because the weld seam is also extremely resilient mechanically, it can be used in structurally relevant areas. The high load-bearing capacity of the FSW seam contributes to vehicle safety. The joints created by FSW are low in distortion due to the low energy input.

Friction Stir Welding: Proven in Series Production

The experts from TPV Automotive and Grenzebach started their cooperation at the Aluminium trade fair in Düsseldorf in 2018. At that time, TPV Automotive placed an order for two FSW gantry machines. These have been running under series conditions in three shifts per day at the Brežice plant since 2020. The gantry machines are integrated into an automatic production line. Here, a robot brings the components to the individual processing stations; it also loads the FSW machines. "The fact that TPV Automotive has integrated four more friction stir welding machines confirms how much the first two machines have proven themselves in series production with demanding quality and time criteria. We are pleased that production output has been significantly ramped up with FSW technology, says Andreas Preßlein, project manager at Grenzebach.

Start With Prototype Welding at Grenzebach

The collaboration between the two companies began with prototype welds at Grenzebach's headquarters in Hamlar near Augsburg in Germany. These were accompanied on site by an expert from TPV Automotive. "Intensive technical sparring with our customers is part of our working philosophy. In this way, we get to know the needs and requirements exactly and can adapt the technology individually and also develop it further together," says Christian Herfert, Head of Friction Stir Welding Technology at Grenzebach.

Emission-Free Process for Green Mobility

Just as electric vehicles aimed at climate-friendly mobility are gaining momentum, friction stir welding is being used more and more frequently for the production of aluminum components. Last but not least, emission-free processes meet low-emission drive technology. Compared with conventional fusion welding processes such as arc welding, friction stir welding requires neither welding wire nor shielding gas or complex exhaust systems. In addition, the application is low-noise and generates no optical radiation.

Two Global Players in Exchange

With TPV Automotive and Grenzebach, two global players meet. TPV Automotive, headquartered in Novo mesto, which lies around 60 kilometers southeast of the Slovenian capital Lubljana and not far from the Croatian border, operates five production facilities in Slovenia, as well as sites in Serbia, the USA and China. The company has more than 60 years of experience in the automotive sector and today employs more than 700 people. TPV Automotive sells its products in more than 20 countries, and numerous well-known automotive manufacturers are among the company's customers.

3,000 Battery Trays per Week

With the six FSW gantry machines from Grenzebach, TPV Automotive can further expand its practical contribution to green mobility. One FSW gantry machine produces around 80 battery trays per day, and the six machines can deliver 3,000 parts per week.

With FSW technology, Grenzebach offers a high-performance and emission-free process for the production of components for e-vehicles. OEMs and Tier 1 suppliers receive comprehensive advice on product design and process and benefit from a large equipment and tooling portfolio that Grenzebach is continuously developing.