External damping of roller bearings and its effect on the acoustics of an e-mobility gearbox

M.Sc. Kai von Schulz, M.Sc. Tilmann Linde, Prof. Dr.-Ing. Steffen Jäger
Furtwangen University, Institute for Product and Service Engineering

Reducing the sound emitted by the vehicle and the noise perceived by the passengers is an essential part of the development of modern (e-)vehicles. Bearings are crucial to the transmission of vibrations within the vehicle powertrain. This article presents a method for studying the impact of external bearing damping on acoustic properties. For this purpose, damping elements between the outer bearing ring and the gearbox housing of a gearbox used in electric vehicles are introduced, and parameters relevant to damping are varied by means of design of experiments.

Noise sources and sound transmission

At first, the noise sources that occur in a gearbox for electric vehicles will be identified. The gear mesh is determined as one of the primary sources of noise. The vibrations generated by the gear mesh are transferred through the shafts, the bearings, and the gearbox housing [1]. The design and material of the gearbox housing play a crucial role in how these vibrations are transmitted and whether they are dampened or amplified [2]. The vibrations can cause resonance in the housing, amplifying the noise emitted from the gear mesh. The air-borne sound emission occurs when the vibrations from gear mesh and structure-borne sound radiate into the surrounding environment. Due to deviations in the ideal meshing, a transmission error occurs between the driving and driven gear. The transmission error is primarily influenced by the manufacturing tolerances, variations in gear tooth geometry, and operational conditions such as load and speed [3]. The design and manufacturing quality of the gears have a considerable impact on their acoustic characteristics [4]. Moreover, the surface roughness of the gear teeth can influence friction and noise generation [5].

Bearings not only transmit the vibrations introduced by the gear mesh, but can also be a source of noise themselves. The primary sources of noise in bearings occur from various factors including design, manufacturing imperfections, operational conditions, and inadequate maintenance [6]. Factors such as load, speed and alignment are of significant importance. Imperfections in the surface finish of the raceways and the balls or rollers, as well as their roundness, can result in an uneven distribution of loads across the bearing surfaces [7]. The presence of high loads or speeds can exacerbate any existing imperfections in the bearing [8].

Finally, the electric motor can also be regarded as a source of perceptible noise. Electric motors, while quieter than internal combustion engines, introduce their own sources of noise, particularly through torque ripple and electromagnetic interference [9]. Torque ripple refers to the variation in torque output as the motor rotates, which can induce additional vibrations in the gearbox [10]. In addition, electromagnetic interference can cause vibrations in the motor’s components, which may be transmitted to the gears through the coupling, thereby further worsening the acoustic behaviour [11].

Potential noise reduction measures

Following the overview of the noise generation mechanisms within the gearbox, it is evident that specific, targeted measures are required to mitigate the associated noise emissions effectively. The primary noise sources, as described in the previous section, are main areas of concern. Targeted measures in these areas can significantly improve the acoustic behaviour of electric vehicle gearboxes. The authors have examined a wide range of measures for reducing the noise of drive systems [4, 12]. The focus of this article is on damping of the excitation by both the tooth mesh and the ball bearings.

The modification of bearing damping characteristics has the potential to result in a reduction in noise levels [13]. Incorporating damping inserts within or around the bearings of a gearbox is an effective method to absorb vibrations at their source before they are transmitted to the gearbox housing. Materials commonly used for these inserts include elastomeric compounds, viscoelastic polymers, and soft metals which are tuned to absorb specific frequencies of vibrations that are prevalent in gearbox operations [14]. These damping elements are usually placed in the most effective locations in the bearing assembly, where they can absorb the vibration energy resulting directly from the interaction between the rolling elements and the raceways.

Design of experiments on external bearing damping configurations

Design of Experiments (DoE) is a statistical approach to study the impact of multiple factors on the systems performance. In the context of analysing external damping of roller bearings, DoE is applied to evaluate how different parameter sets affect the transfer of the vibrations. DoE is particularly useful in this context, as it enables the identification of the most influential factors affecting both noise levels and efficiency, as well as the optimal combination of these parameters.

The variables in this case are the number of O-rings, their rigidity and the cord thickness of the O-rings, and whether additional oil is pressed into the gaps or not. By allowing simultaneous variation of parameters, DoE not only saves time and resources but also uncovers interactions between these parameters that might otherwise remain hidden. In this way, DoE provides a more comprehensive understanding of how the variables work together to influence the system’s behaviour, revealing possible synergies or trade-offs between different parameters. Here, the focus is on the system’s response in terms of its structure-borne and airborne sound emissions. Additionally, the system efficiency is analysed. For example, reducing the stiffness of the O-rings may reduce the transferred vibration, but it may also reduce efficiency due to a higher transmission error in the tooth mesh. The application of DoE allows the reduction of the number of experimental runs while maintaining the comprehensive coverage of the interactions and effects of all factors within the specified range. This efficiency in test design is critical in experimental research involving complex mechanical systems, where a large number of tests could be impractical due to time, cost, or resource constraints.

Physical study

To evaluate the presented measure of outer bearing damping, an existing high-speed gear test rig (cf. Figure 1) is being converted so that different parameter sets of outer bearing damping can be tested for their effectiveness under different operating conditions, such as speed and torque.

Fig. 1 Gear pair test rig.

For this purpose, the bearing seats have been modified to allow the use of up to three commercially available nitrile rubber O-rings. In addition, it is possible to fill the spaces between the O-rings with oil and apply an overpressure. Figure 2 shows a schematic illustration of the design.

Figure 2 CAD geometry of outer bearing damping design.

In this study, the experimental parameters are varied within specific ranges, providing valuable insights into their effects on system behaviour. Various tests are carried out at different torques and speeds in the range between 0 and 6000 rpm and 0 and 45 Nm. The measurement results are analysed at static operating points. The experimental design includes varying the number of O-rings from 1 to 3 and varying the stiffness of the O-rings between 70 and 90 Shore. In addition, the cord thickness of the O-rings is varied between 1.8 mm and 2.8 mm and whether additional oil is injected into the gaps is also considered as a binary factor (yes/no). Through the application of DoE, this study aims to determine the optimal combination of these factors to achieve an appropriate damping characteristic: significantly reducing noise while maintaining high efficiency.

Once the test rig has been converted and the measurement campaign has been completed, the most promising damping elements will be further optimised.

Authors

M.Sc. Kai von Schulz: Kai.vonSchulz@hs-furtwangen.de
M.Sc. Tilmann Linde: tilmann.linde@hs-furtwangen.de
Prof. Dr.-Ing. Steffen Jäger: steffen.jaeger@hs-furtwangen.de

References
[1] Tosun, M., Yildiz, M. u. Ozkan, A.: Investigation of Gearbox Noise and Comparison of Varying Transfer Path Analysis Methods. SAE Technical Paper 2017-01-1867, 2017
[2] Amaral, D. R., Ichchou, M. N., Kołakowski, P., Fossat, P. u. Salvia, M.: Lightweight gearbox housing with enhanced vibro-acoustic behavior through the use of locally resonant metamaterials. Applied Acoustics 210 (2023), S. 109435
[3] Heider, M. K.: Schwingungsverhalten von Zahnradgetrieben. Beurteilung und Optimierung des Schwingungsverhaltens von Stirnrad- und Planetengetrieben. Zugl.: München, Techn. Univ., Diss., 2012. Dissertationen der FZG / Forschungsstelle für Zahnräder und Getriebebau, Technische Universität München, Bd. 185. München: Verl. Dr. Hut 2012
[4] Schulz, K. von, Linde, T. u. Jäger, S.: Profile Modifications for Gears and their Effect on the NVH Behaviour of an Electric Vehicle Gearbox. 2024 Stuttgart International Symposium on Automotive and Engine Technology. Stuttgart 2024
[5] Zhao, X. u. Vacca, A.: Analysis of continuous-contact helical gear pumps through numerical modeling and experimental validation. Mechanical Systems and Signal Processing 109 (2018), S. 352– 378
[6] Adamczak, S., Stępień, K. u. Wrzochal, M.: Comparative Study of Measurement Systems Used to Evaluate Vibrations of Rolling Bearings. 1877-7058 192 (2017), S. 971–975
[7] Mohd Yusof, N. F. u. Ripin, Z. M.: Analysis of Surface Parameters and Vibration of Roller Bearing. Tribology Transactions 57 (2014) 4, S. 715–729
[8] Wang, Z., Yang, J. u. Guo, Y.: Unknown fault feature extraction of rolling bearings under variable speed conditions based on statistical complexity measures. Mechanical Systems and Signal Processing 172 (2022), S. 108964
[9] Gong, C., Zhang, P., He, S. u. G S J, G.: E-motor NVH Analysis for PWM Induced Current Ripples in EV Applications. 2022 IEEE Energy Conversion Congress and Exposition (ECCE). IEEE 2022, S. 1–5
[10] Novak, W.: Geräusch- und Wirkungsgradoptimierung bei Fahrzeuggetrieben durch Festradentkopplung, Universität Stuttgart Dissertation. Stuttgart 2010
[11] Kim, S. J., Kim, K., Hwang, T., Park, J., Jeong, H., Kim, T. u. Youn, B. D.: Motor-current-based electromagnetic interference de-noising method for rolling element bearing diagnosis using acoustic emission sensors. Measurement 193 (2022), S. 110912
[12] Schulz, K. von, Linde, T. u. Jäger, S.: Measures to reduce the noise emission of a gearbox for electric vehicles. Tagungsband Tribologie-Fachtagung 2024. 2024, S. 394–403
[13] Tsuha, N. A. H. u. Cavalca, K. L.: Stiffness and damping of elastohydrodynamic line contact applied to cylindrical roller bearing dynamic model. Journal of Sound and Vibration 481 (2020), S. 115444
[14] Turnbull, R., Rahmani, R. u. Rahnejat, H.: The effect of outer ring elastodynamics on vibration and power loss of radial ball bearings. Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 234 (2020) 4, S. 707–722

Dog clutch without angular backlash

Gabriela Achtenova, Michal Jasný, Jiri Pakosta, Rômulo do Nascimento Rodrigues
Center of Vehicles for Sustainable Mobility, Czech Technical University in Prague

Dog clutches are cost-effective but often suffer from angular backlash, causing discomfort. A novel, patented design has been developed to eliminate this issue using a purely mechanical blocking mechanism. This design, fully interchangeable with conventional mechanisms, requires no extra modifications but needs an external synchronization system.

Featuring innovative gearshift dogs and blocking mechanisms, it was tested with two prototypes on test benches. The results showed the design’s effectiveness, and robustness especially for hybrid and electric vehicles, addressing key shortcomings of traditional clutches.

Introduction
Greenhouse gases, CO2 regulations, alternative fuels, and vehicle electrification are critical issues driving the rapid growth of hybrid (HEV) and electric vehicles (EV) [1]. This shift demands innovative solutions in automotive engineering. This research focuses on developing a new gearshift mechanism to meet these demands. In HEVs and EVs, the electric motor can act as an external synchronization mechanism, potentially reducing costs. Parallel hybrids, requiring a wide range of gear ratios, benefit from cost-effective gearboxes like manual parallel shaft gearboxes (MT) or automated versions (AMT) [2][3]. These gearboxes commonly use synchronizers, a prevalent gearshift mechanism in passenger cars [4].

This research aims to replace the synchronizer with a new, cost-effective gearshift mechanism that eliminates the need for synchronization while maintaining or surpassing the synchronizer’s functions [5]. Typically, a dog clutch is the simplest gearshift mechanism for constant mesh gears but has been limited by driving comfort and NVH (Noise, Vibration, and Harshness) concerns. In electric powertrains, NVH issues include gear whine and gearshift mechanisms [4],[6]. Reducing angular backlash is crucial for minimizing NVH, a feature of the new mechanism, while ensuring cost-effectiveness and compactness. More compact gearboxes tend to be stiffer, further reducing NVH [7].

This research introduces a patented dog clutch design addressing angular backlash, a common issue in traditional mechanisms [7]. Using a purely mechanical blocking system, it minimizes backlash and improves shifting quality. The form of dogs enables very fast disengagement of the speed even under load. Rigorous prototype testing confirmed its functionality, durability, and comfort, making it suitable for vehicle gearboxes.

Final design of dog clutch with blockchain mechanism

The clutch assembly (Figure 1) includes a hub (1) on the gearbox shaft, a sliding gear (2) that moves axially to engage gears, a gearshift sleeve (3) for controlling movement, and a blocking ring (4) to secure the sliding gear in positions. The sliding gear is split into two halves connected by screws (5) and pins (6). One blocking ring locks the sliding gear in all three positions (engaged/neutral/engaged) and secures the gearshift sleeve in neutral. No changes to the standard MT/AMT gear selector mechanism are needed. The design’s uniqueness is confirmed by Patent No. 307443[8] and the utility model „Schaltungskupplung“ [9]. Following design optimization, prototypes of dog clutches with a blocking mechanism were produced. Two clutches for the MQ200 gearbox were made to engage 1st, 2nd, 3rd, and 4th gears, see Figure 2. The prototype production was funded and supported by ŠKODA AUTO.

Gearshift process

The blocking ring stays concentric with the hub due to its constant contact with the sliding gear or gearshift sleeve. With six contact points, the ring maintains its shape during compression. To prevent uneven deformation, which could interfere with gear movement and cause excessive wear, the ring’s ends are bent inward. Figure 3 illustrates the gearshift process, where shifting the right gear involves:
Position 1 – neutral:Black arrows show axial backlash between the sliding gear and the gearshift sleeve. The blocking ring holds both components – sliding gear (upper) and sleeve (lower) – in neutral;
Position 2 – engagement preparation:The sleeve moves right, compressing the blocking ring, while the sliding gear remains in neutral until backlash is resolved;
Position 3 – engagement in process:With backlash removed, the sleeve pushes the sliding gear right, and the blocking ring stays compressed;
Position 4 – engagement termination:The sliding gear reaches its maximum position, engaging the gearshift dogs. Both components stop moving axially, and the blocking ring is no longer compressed;
Position 5 – engaged: The blocking ring expands back to its original position, fitting into the sliding gear’s groove, preventing clutch disengagement due to torque;

Position 6 – disengagement preparation:The sleeve moves left to compress the blocking ring. Axial backlash is present, keeping the sliding gear engaged;
Position 7 – disengagement in progress:The blocking ring is fully compressed, backlash is gone. The sleeve moves the sliding gear to
Position 8 – Disengagement Termination: The sleeve reaches neutral, but the sliding gear remains slightly engaged due to kinetic energy. The decompressing blocking ring helps move the gear to neutral;
Position 9 – Neutral:The dog clutch returns to the neutral position, same as Position 1.

Prototypes of the clutch were designed for the MQ200 gearbox, where the blocking ring withstands axial forces up to 2 kN during dog engagement, transferring a maximum torque of 200 Nm. The force needed to engage and disengage the clutch via the gearshift sleeve is about 45 N, which is well within permissible limits and comparable to manual shifting forces. The sliding gear and gearshift sleeve have been optimized for powder metallurgy. For the sliding gear, only grooves for the blocking rings and threads on one half need machining, while the gearshift sleeve requires machining of the inner groove for the neutral position. The outer groove, for the gear selector fork, is for prototype compatibility and can be omitted in future designs. No additional parts are required between the sliding gear and gearshift sleeve, ensuring concentric alignment with the hub. The blocking ring is fixed securely and cannot rotate around the shaft axis due to the pin.

Verification of the dog clutch

The fulfillment of the requirements for the dog clutch with a blocking mechanism needed to be validated against the design specifications. First experiments were static to verify the shift force and unwanted disengagement. The resulting gearshift force required to compress the blocking ring was measured to be 45 N.

Further was experimentally tested that the blocking ring functions as intended, preventing unwanted disengagement of the clutch.

The dynamic tests were dedicated for verification of function and for endurance tests. The first phase of clutch prototype testing used an inertia test bench with the output shaft connected to a large inertia disc. Tests focused on smooth shift sleeve movement and proper engagement / disengagement of the dogs. No unexpected behavior was observed.

The gearbox was connected to the gearshift robot on the inertia test stand, and gearshifts were performed with various input parameters. Mismatch speed was controlled by the difference between the stationary input shaft and the rotating wheel or by gear ratios between two gears. Figure 4 shows data from a gearshift with 3rd gear engaged at a mismatch speed of 30 RPM. The gearshift process began at 0.96 s, with rising displacement and force curves. A sharp drop in force at 1.02 s indicated compression of the blocking ring, allowing the sliding gear to move. The force increased as the dogs engaged, and by 1.08 s, engagement was complete. The gearshift took about 60 ms.

To proceed with dynamic check of the blocking mechanism, the gearbox was moved to dynamometric test bench. The function for the 3rd and 4th gears were performed with positive result. Due to test bench capacity 1st and 2nd speed were not tested.

Service life (endurance) tests were conducted for the 3rd and 4th gear clutches on the inertia test bench, with each gear being shifted 180,000 times and the gearbox output set to 89 RPM. This low speed simulated a mismatch speed of around 140 RPM, optimizing the gearshift process and eliminating the need for external synchronization. Each shift took just over 2 seconds, resulting in 220 hours of continuous testing per clutch and blocking ring.

Conclusion

The new patented dog clutch with a blocking mechanism enhances efficiency and reduces costs for electric and hybrid vehicles. It offers minimal angular backlash (less than 0.1°) and can disengage under load, improving shifting comfort and torque transmission. This purely mechanical design is compatible with standard gear selectors, including sequential shifting, and requires no additional modifications. The clutch’s blocking ring withstands high axial forces, preventing unwanted disengagement. Prototypes, tested in a standard five-speed gearbox, demonstrated up to 30 mm axial space savings compared to conventional synchronizers. The design supports effective serial production using powder metallurgy and has proven durability with a service life of 700,000 cycles.

References
[1] PILLOT, Christophe. The Rechargeable Battery Market and Main Trends 2020-2030. Lyon: Avicenne Energy, 2022.
[2] HOFMANN, Peter. Hybridfahrzeuge – Ein alternatives Antriebssystem für die Zukunft. Switzerland : Springer, 2014. Second edition. ISBN: 978-3-7091-1780-4
[3] NAUNHEIMER, Harald et al. Automotive Transmissions: Fundamentals, Selection, Design and Application. Berlin : Springer-Verlag, 2011. ISBN 978-3-642-16216-8.
[4] FISCHER, Robert et al. The Automotive Transmission Book. Switzerland: Springer International Publishing, 2015. ISBN 978-3-319-05262-5.
[5] MEHRGOU, Mehdi et al. NVH Aspects of Electric Drives-Integration of Electric Machine, Gearbox and Inverter. 2018. SAE Technical Paper 2018-01-1556. doi: 10.4271/2018-011556. ISSN 0148-7191.
[6] Wu,G.,Zhang, X.,& Dong, Z. (2015). Powertrain architectures of electrified vehicles: Review, classification and comparison. Journal of the Franklin Institute, 352(2), 425–448. doi: 10.1016/j.jfranklin.2014.04.018
[7] TŮMA Jiří. Vehicle Gearbox Noise and Vibration. New Delhi: John Wiley & Sons, Ltd., 2014. ISBN 978-1-118-35941-9.
[8] ČESKÉ VYSOKÉ UČENÍ TECHNICKÉ V PRAZE, FAKULTA STROJNÍ. Řadící spojka. Inventors: JASNÝ, M., G. ACHTENOVÁ and J. PAKOSTA. File No. MPT F 16 D 11/10. Patent No. 307443. 22. August 2018. Czech Office of Industrial Property. Patent.
[9] SCHECHISCHE TECHNISCHE UNIVERSITÄT IN PRAG, FAKULTÄT FÜR MASCHINENBAU. Schaltungskupplung. Inventors: JASNÝ, M., G. ACHTENOVÁ and J. PAKOSTA. IPC-Class F16D 11/00 (2006.01). File No. DE: 20 2018 103 633.5. 26. June 2018. Deutsches Patent- und Markenamt. Utility model.

Driving sustainability – Reducing the embedded emissions of copper in electric vehicles

Bruno De Wachter, Independent Advisor, International Copper Association

Since the publication of the EU Green Deal, e-mobility OEMs and Tier 1 suppliers in Europe have been actively seeking ways to evolve towards carbon neutrality. For such a journey to be successful, open  communication across the entire value chain is essential. This article develops the case for copper, a key raw material of the EV powertrain.

Copper in EVs – There is great potential to significantly reduce embedded GHG emissions associated with copper in the years to come.

Copper has the highest electrical conductivity of all non-precious metals, a quality put to good use in the stator windings of electric motors and induction motor rotors, as well as batteries, cabling and electrical connections. As OEMs and Tier 1 automotive industry suppliers develop their decarbonization plans, reducing copper’s embedded greenhouse gas (GHG) emissions is one of the challenges. A common approach to achieving this is by setting out a series of KPIs and milestones for their copper suppliers.

The good news is that there is certainly potential for reducing the carbon emissions from copper production to net-zero over the coming 30 years, and without the need for major technological breakthroughs. But for these conditions imposed by manufacturers in the automotive industry to be effective and actually help the copper industry speed up their decarbonization process, they have to be formulated in the right way, which requires some insight into the copper production process and material flows.

The copper production process and its emissions

A whole sequence of processing steps is required to produce high purity copper. The process of extracting primary copper from ores begins, of course, with mining, followed by concentration through a flotation process, and a first stage of refining in smelters using pyrometallurgical methods. The material is then subjected to a second stage of refining through electrolysis. An alternative route for low grade ore is the hydrometallurgical process, which separates the copper from the ore through leaching and then extracts it from the remaining solution through electrowinning.

Secondary copper is produced from scrap originating from manufacturing processes or end-of-life products. High purity scrap can be remelted directly with no need for refining, while less pure scrap requires additional processing. This can take place in dedicated secondary smelters, or the material can be added to the primary production process at various stages, depending on the scrap’s purity. This means that high-quality copper metal is often produced from a combination of primary and secondary sources.

According to an analysis by the International Copper Association (ICA), copper production currently leads to a total of 97 million tonnes of GHG emissions annually, or 0.2% of total global emissions. Of these emissions, approximately 70% are generated by mining, 23% originate from smelting and refining, and the remaining 7% come from upstream and downstream transport and end-of-life treatment of products.

A major component of the GHG emissions associated with primary copper comes from electricity, from fossil fuels used in mining transport and equipment, and from fuels used in smelting furnaces at various stages of the production process. The GHG emissions of secondary copper depend on the purity of the scrap, since this determines at what stage in the refining process it is added, but they are generally lower than those from primary copper. That said, using secondary copper can never be the sole and complete solution to decarbonization, as explained later. For this reason, reducing the impact of the primary production routes should receive major focus in the decarbonization process.

The pathway to net-zero

The decarbonization of the copper production process has already started, with numerous initiatives by individual companies involved in copper mining and refining. To step up the momentum, the ICA with its members developed a path forward to bring the carbon foot print of copper production as close as possible to net zero by 2050 (’Copper – The Pathway to Net Zero’). Made public in March 2023, the Pathway sets out a pragmatic approach to decarbonizing copper production, using existing technologies. It delineates which decarbonization options can be activated, by when, and with what impact. It also outlines some enabling conditions that should be in place to achieve this.

For scope 1 and scope 2 emissions, the Pathway identifies four major types of levers. The first is equipment electrification, to include the haulage trucks used in mining. An example of good practice is demonstrated by Boliden, a Swedish mining company which introduced electric trolley assistance in its haulage trucks in 2018, saving significant amounts of diesel fuel (Boliden, 2018). At the same time, underground mining machinery is being electrified at a rapid pace, coming with the additional benefit of saving the energy and cost of ventilation. The second lever is decarbonizing the electricity supply. This includes switching from standard to green electricity, alongside the option of installing wind and solar energy farms at copper production sites. A third lever is replacing fossil fuels with biofuel, biogas, or green hydrogen, particularly in smelting furnaces. A fine example of this is at German copper producer Aurubis, which has started using hydrogen instead of natural gas for the reduction process in its anode furnaces – an innovation set to reduce GHG emissions by around 5,000 tonnes each year (Aurubis, 2023). The fourth major lever encompasses various kinds of energy efficiency improvements at various stages of the production process. In a collective commitment, ICA members declared that they will be applying these and other measures to reduce their scope 1 and 2 emissions by 30 to 40% by 2030, 70 to 80% by 2040, and 85 to 95% by 2050.

A similar approach has been followed for scope 3 emissions, subject to the proviso that the results for this category depend on all the actors in the value chain collaborating. ICA members aim to reduce these emissions as far as possible by 2050, and will do what they can to unite every stakeholder behind this goal.

Recycling and decarbonization

Copper’s infinite recyclability is a major advantage. About 80 percent of copper is used in an unalloyed form, making the recycling process more straightforward. Even for copper that is alloyed or contains other materials, recycling can still be achieved without downgrading. Unwanted elements can be efficiently removed to recover the copper in its pure state, ready to be re-used in any kind of application. Because of its high degree of recyclability, copper already in use in its various applications is not regarded as lost, but can instead be legitimately considered part of the world’s copper reserve, often referred to as society’s „urban mine”.

Its high level of recyclability, combined with the fact that copper from secondary sources produces fewer GHG emissions than primary sourced copper, could lead to the simplistic conclusion that increasing the share of secondary material would be a good strategy for reducing embedded emissions. While this solution will work at individual plant level, it does not make sense on a European or world wide scale. Due to the long average lifetime of products using copper (typically 25 to 30 years) and strong growth in copper demand (practically doubling every 30 years), the availability of end-of-life material is far too limited to meet the demand for new material. Additionally, no process is 100% efficient, and there will always be losses associated with collecting, separating, and re-processing copper scrap.

Note that a distinction should be made between fabrication scrap, which originates from the production of end-use material out of semi-finished goods, and end-of-life scrap, which originates from end-of-life products.

Globally, scrap recycling rates from end-of-life products averaged around just 15% over the period from 2000 to 2020. Estimating future recycling rates is complicated by various uncertainties, but MineSpans by McKinsey expects the end-of-life recycling input rate to increase to 23 percent over the next 30 years.

Fabrication scrap contributed to about 16% of semi-finished goods production globally, a figure expected to remain stable. Bearing this in mind, any requirement set by raw material purchasers to increase the total recycled content of new copper above 35%-40% can only result in less recycled material being used elsewhere, leading to zero net reduction in GHG emissions at global level.

Moreover, the main levers for increasing recycling rates are in the collection and separation of end-of-life material, and consequently not in the hands of copper producing companies. Design engineers at every level of the automotive industry can play their role by favouring product designs that facilitate dismantling and separation at end-of-life (“design for recycling”). In some cases, collaborations between various stakeholders and the copper industry to capture and process the cleanest scrap and create a closed loop can set a good example. Recycling rates could also benefit from incentives for end-of-life collection, from staff upskilling for end-of-life management, and from improved separation techniques for treating multi metal scrap streams. Improved systems for car registration and waste stream reporting could avoid end-of-life vehicles being exported from the EU or going under the radar in other ways.

Collaboration across the value chain

All this considered, e-mobility OEMs and Tier 1 suppliers should not be over-concerned about the feasibility of reducing the embedded GHG emissions of copper conductors. The ICA and its members have developed a decarbonization pathway for the next 30 years based on existing technologies and that will bring the carbon footprint of copper production as close as possible to net zero by 2050. But to unlock its full potential, the pathway depends on stakeholder across the value chain communicating and collaborating with each other, upstream from copper production as well as downstream.

Purchase managers from the automotive industry can work with their copper suppliers to develop a roadmap to reduce embedded emissions and offer collaboration avenues to accelerate the process.

Raw material sourcing managers responsible for purchasing copper products should be aware of the limits of using recycled content as a means of reducing embedded GHG emissions. At the same time, they could consider developing closed loop business models for copper used in the automotive industry. Design engineers can play their role in this process by facilitating dismantling and separation at end-of-life.

With this level of collaboration across the entire value chain – stake holders communicating and interacting and achieving what is within their reach – there is great potential to significantly reduce embedded GHG emissions associated with copper in the years to come, while improving the collection and recovery rates of copper in end-of-life vehicles.