New findings on bending and welding behavior in the hairpin stator process chain

At this year's Coiltech Pordenone, an important development project by a consortium consisting of Gehring Technologies GmbH + Co KG, Wafios AG, Aurubis AG and Schwering & Hasse Elektrodraht GmbH will be presented, which provides new insights along the value chain for the production of hairpin stators. Under the title "Bending and welding behavior with different copper materials in the hairpin stator process chain", leading companies from the copper industry, wire industry and mechanical engineering have jointly investigated over a period of around 1.5 years how different copper grades affect the production process.

Aurubis provided three different copper materials for the tests: Cu-OFE, Cu-ETP1 and a Cu-ETP1 with a significantly reduced oxygen content. The main difference between these material grades lies in the oxygen content, which is specifically adjusted using various manufacturing processes. Cu-OFE is a high-purity and oxygen-free copper; Cu-ETP1 is also a high-purity copper with high availability and very good processability with economic advantages over Cu-OFE.

At SHWire, the starting material was then processed into automotive-grade flat wires for hairpin processes. The task here was to change the mechanical properties of the flat wire in such a way that their effects on the subsequent bending and welding processes could be investigated. This was achieved through a special design of the drawing and enameling process, which changes the physical crystal structure of the copper. All process and production parameters were continuously monitored via the highly automated "FIT" production monitoring platform to ensure consistent propertiesfor each section. This ensured the subsequent performance of valid bending and welding tests.

The enameled wire was then used for bending tests at Wafios. The main focus was on the scattering of the bending angle of the different batches. In addition, the enameled wire was mechanically stripped to prepare it for welding tests.

Gehring carried out welding tests on the wires with different qualities of copper. In order to assess the quality of the weld seams, they were evaluated using X-ray and micrographs. The microstructure in the welding and heat-affected zone of the copper materials was analyzed, as well as any pores that formed and the oxygen content determined. In addition, tensile tests were carried out to determine the mechanical strength. The results of the individual tests will be presented at Coiltech 2024 in Pordenone, Italy. This application-oriented development provides valuable insights for the optimization of the investigated manufacturing processes and the quality assurance of hairpin stators.

Gehring and Wafios present electromobility of the future

Furthermore, the two long-established companies Gehring and Wafios will once again have a joint stand at COILTECH 2024 and present innovative solutions for e-motor construction. Since April 2021, they have been pooling their expertise to offer the automotive industry complete turnkey production lines. At the international trade fair, they will be presenting comprehensive solutions for prototype, sample and individual construction as well as for large-scale production. The focus will be on the SpeedFormer transfer bending system from Wafios, which is a revolutionary bending concept for the series production of hairpins. Gehring will also be presenting its expertise as a supplier of complete production lines. The joint strategy has already aroused great interest and will be further expanded at COILTECH ITALIA 2024.

For more information and detailed results, visit Gehring/Wafios at Coiltech 2024 in Pordenone, booth: Hall 7 Stand B22

Caption: Welding beads on the winding head of a hairpin stator in the Gehring SWD machine system - precision and technology combined for high-performance electric motors, photo: Gehring

Caption: Laser welding of hairpin ends on the SWD machine: precision and process expertise for the highest stator quality, photo: Gehring

Caption: Flat hairpin geometry and compact cage dimensions with the new HQ bending system from WAFIOS, photo: WAFIOS