Mercedes-Benz Axial Flux Motor Large-Scale Production

Mercedes-Benz has commenced large-scale production of its electric axial flux motor at the Berlin-Marienfelde plant. This high-performance, compact motor is debuting in the Mercedes-AMG GT 4-door Coupé, marking a transition from a technological prototype to an industrial reality.

Axial Flux vs. Radial Flux Technology

An axial flux motor differs from conventional radial flux motors by the direction of the electromagnetic flux, which runs parallel to the axis of rotation rather than perpendicular to it. In this design, two rotor discs sandwich a central stator, creating a pancake-like form factor.

This architecture provides several technical advantages:

  • High Power Density: The design allows for a more compact motor with higher torque and power output relative to its size.
  • Compact Packaging: In the Mercedes-AMG GT 4-door Coupé, the front-axle motor is approximately 9 cm wide, while the two rear-axle motors are approximately 8 cm wide each.
  • Performance Gains: The technology enables the fully electric performance model to accelerate from 0 to 100 km/h in as little as 2.1 seconds, reaching top speeds of 300 km/h with the Driver’s Package.

Industrialization and Manufacturing Innovations

Moving axial flux technology from a prototype to mass production required the development of 35 globally new manufacturing processes and over 30 patent applications. The production facility spans 30,000 square meters across three halls and seven production lines, involving 98 total process steps.

Advanced Component Fabrication

  • Rectangular Copper Wire: To maximize copper density within the stator, Mercedes-Benz developed a specialized process to bend rectangular copper wire at high speeds into tight radii without damaging the insulation or causing folds.
  • Laser Interconnection: Due to extremely limited space, the copper wire ends are joined using high-precision laser welding, which minimizes thermal energy input to protect surrounding plastic structures.
  • AI-Driven Polymer Welding: The assembly uses simultaneous laser transmission welding for plastic parts. AI-powered optical real-time quality control and image processing ensure precise component placement and prevent damage to sensitive areas.

The "Wedding" Assembly Process

  • High-Precision End Assembly: The final assembly, termed the "wedding," involves positioning the stator between two magnetic rotor discs.
  • Magnetic Force Management: The process must manage magnetic forces of up to 9 kN (approximately 900 kg) while maintaining the stator within a tolerance of less than 0.1 mm in the magnetic center plane. This is achieved via a high-frequency control algorithm that corrects the position in the final 0.5 seconds of the process.

Strategic Integration and Origin

The technology is based on the work of British electric motor specialist YASA, which Mercedes-Benz acquired as a wholly-owned subsidiary in 2021. Since the acquisition, Mercedes-Benz has refined the product and the manufacturing processes to meet the demands of automotive mass production and long-term durability.

Technical Community Perspectives

While the announcement highlights a leap in manufacturing, technical discussions among engineers and enthusiasts suggest a nuanced view of the technology's impact:

  • Reliability vs. Performance: Some observers note that while axial flux motors offer superior power density, they face higher loads and stresses and require tighter tolerances than battle-tested radial flux motors.
  • Mass Market Viability: There is a consensus that radial flux motors will likely remain the standard for mass-market vehicles for the next decade because they are "good enough" and more proven in terms of reliability.
  • Manufacturing as the Real Achievement: Several commentators emphasized that the primary breakthrough is not the motor design itself, but the ability to mass-produce such a complex geometry reliably.

"The main benefit here seems to be smaller and lighter for the same power output... Radial is already highly efficient, reasonably light and small. The real level for weight is the battery."

"Going from a prototype to something you can mass produce reliably is often the hard part."

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