Product and Production Concepts for the Variant-flexible Hairpin Stator Production


The ongoing electrification of the global vehicle fleet is leading to an increasing relevance of electric traction drives (short: e-drives) in the automotive industry. In the future, almost every road vehicle will have at least one electric motor regardless of whether it is a battery-powered vehicle, a vehicle with a fuel cell, or a mild or plug-in hybrid.

A central field of innovation for e-drives is the stator production in the hairpin design. Contrary to conventional wire winding technology, the hairpin technology uses a plug-in coil structure of solid copper electrical conductors for the windings of the electric motor. For this purpose, copper wires are first bent three-dimensionally into a U-shape and then completed into an electrically closed "winding" by means of various assembly, forming and contacting operations. The name "hairpin" is derived from the hairpin-shaped geometry of the copper conductors. The innovation potential lies in the assembly-oriented structure of hairpin stators, which on the one hand enables more compact and powerful traction drives and on the other hand more economical production processes suitable for large series.

Despite recent improvements in the development of flexible manufacturing technologies for hairpin stators, current approaches usually rely on highly restricted product designs as well as redundant and costly production systems. In view of the increasing demand of e-drives for traction applications, economically efficient manufacturing approaches and methods are required to address the aspect of variant flexibility under the premise of automotive requirements for high process stability.

Research Goal

The research goal consists in the development and testing of a system of hairpin stator and production process concepts with regard to variant-flexibility and process stability. For this purpose, a reference production line of hairpin stators covering all process steps from wire forming to secondary insulation of the winding heads is built. The reference line hence enables a holistic study of the entire process chain to identify interdependencies between product features and production process steps, such as the influences of different wire thicknesses on the laser contacting of the copper wires.

Research activities and procedure

The specific sub-goals are:

  • Development of innovative hairpin stator product concepts their subsequent testing at both the level of individual process steps as well as at the level of the entire process chain.
  • Investigation of the extent to which product or manufacturing changes as well as production technologies of different levels of maturity can be quickly integrated into the reference process chain.
  • Identification of cause-and-effect relationships between product features and process parameters to increase process flexibility and process stability in the hairpin stator production.

Research and project partners

  • PEM of RWTH Aachen University
  • DAP of RWTH Aachen University
  • Ford Werke GmbH Köln
  • ENGIRO GmbH Aachen
  • AMS Anlagenbau GmbH & Co. KG Vlotho
  • Berg & Co. GmbH Bielefeld
  • thyssenkrupp System Engineering GmbH Bremen


08/15/2020 through 08/14/2023

Project Management Agency

Projektträger Jülich (PtJ)

Funding Authority

Ministry of Economic Affairs, Innovation, Digitalization and Energy of the State of North Rhine-Westphalia



Benjamin N. Dorn



+49 1511 5621064


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