August 2024 Volume 6

SUSTAINABLE INNOVATIONS FOR A GREEN FUTURE A Step Forward for Ecologically Friendly Rotor Shaft Production By Dr.-Ing. Nadezda Missal and Stefanie Schwertel ENERGY

A ccording to the new EU deal on the potential elimination of combustion engines, from 1st January 2035, only new CO2 neutral cars could be registered [1]. Recently, adopted exemp tion for alternative technologies allows the application of e-fuels, but due to the significantly lower efficiency of e-fuels [2], the production of electric cars is expected to dominate the automotive industry and accelerate the radical switch to electric drives. This change poses an immense challenge for automotive suppliers because an entire range of components will be omitted or must be completely redevel oped. Usually, this causes the existing manufacturing technology to be unsuitable for producing of such newly developed components. Moreover, the requirements on suppliers concerning the quantifi cation of the product carbon footprint (PCF) during component production are tightening which is increasingly deciding the choice of manufacturing process. Bulk metal forming, especially cold metal forming plays a key role in the production of vehicle components worldwide in terms of light weight design, accuracy, productivity, and sustainability. Due to the full material utilization and the elimination of additional heating, cold forming offers great potential as a more sustainable and envi ronmentally friendly manufacturing solution to reduce the CO2 footprint compared to other manufacturing technologies such as machining or forging. The Felss Group was founded in 1905 as a traditional company in the field of cold metal forming. Felss core technologies rotary swaging and axial forming offer innovative solutions for the forming of tubes and solid materials for the automotive industry with a focus on light weight design potential. In addition to the increasing importance of environmental aspects, Felss concentrates its development resources on the needs of its customers, including the growing interest in elec tric vehicles. This has resulted in completely new forming processes and the further development of the existing core technologies of rotary swaging and axial forming, including the optimal design of the process chain for the production of rotor shafts. The individual advantages of rotary swaging and axial forming are exploited in this process chain to achieve a particularly sustainable and environmen tally friendly production process. The commercially available geometries of rotor shafts and the possible manufacturing technologies for their production were already inves tigated in IMU Study 71. These can be divided into assembled,

solid, hollow as drilled from a bar or hollow from a tube and are manufactured by machining, forging, multi-part welding, or cold forming processes. To determine the potential economic and ecological advantages of rotor shafts produced by rotary swaging compared to other manufac turing technologies, a load- and process-optimized rotor shaft geom etry was developed, as shown in Figure 1. This meets the following requirements: • Lightweight design through targeted load-optimized wall thick ness distribution. • A hollow design for internal cooling. • High precision for stable and precise torque transmission at high rotational speeds. • The use of splines or helical gearing for torque transmission.

Figure 1: Load-optimized rotor shaft geometry with a specifically optimized wall thickness distribution. The corresponding newly developed process chain from Felss (Figure 2) for the manufacturing of the hollow rotor shafts (Figure 1) from a tube could be carried out almost exclusively by cold metal forming, especially by rotary swaging and axial forming. Besides the hard ening process and the turning operations to perform minimal machining of the end faces after hardening, the process chain is carried out without additional heating, welding, or other energy and material inefficiency.

FIA MAGAZINE | AUGUST 2024 12