Dr David Moule, an expert in electric drives with a passion for sustainability, tells Louise Davis about some valuable work focused on recycling and reusing the magnets used in motors
Dr David Moule, an expert in electric drives with a passion for sustainability, tells Louise Davis about some valuable work focused on recycling and reusing the magnets used in motors
Electric drives technical specialist at ZF’s Servo Drives Centre of Competence, Dr David Moule, recalls how a shared interest in best practices concerning magnet recycling led to a major European project on the recycling and reuse of rare earth materials. “ZF has worked with the University of Birmingham around magnets and related technologies for some time. Around 10 years ago Professor Allan Walton and I started discussing the technologies the university had developed for the recycling of magnets using hydrogen,” begins Moule.
Discussing his own inspiration, Moule notes: “I understood that in future, the ability to recycle magnets efficiently would be very useful. I remembered when insufficient facilities were available to deal with the environmentally damaging gases present in end-of-life fridges and freezers in the early 2000s – resulting in ‘fridge mountains’ awaiting safe processing. Technologies would be needed to ensure that the same mistakes weren’t made as we aimed to electrify transport.”
Moule explains that, following the university pioneering the use of hydrogen in the manufacture of magnets, “ZF subsequently joined a consortium that Professor Walton was assembling to bid for a European project. That became SUSMAGPRO, which stands for Sustainable Recovery, Reprocessing and Reuse of Rare Earth Magnets in a European Circular Economy.”
The work of the four-year project – and that Moule and his team at ZF continue to focus on – centred on the recycling of systems such as motors containing neodymium (known as NdFeB) magnets. Metallic elements such as neodymium and other rare earth metals are classed as critical raw materials by the EU. “These magnets find considerable use in automotive applications such as traction motors, and auxiliaries such as high-performance steering and braking systems. The same materials are also used in wind power generators, hard disk drives, loudspeakers, and many other motor applications,” details Moule. “Through the work with Professor Walton and his team we wished to understand how rare earth metals used in magnets could be efficiently recycled. To do this we needed to understand the process – and the things that will contaminate the process. This understanding would enable us to make design changes to our products, allowing them to be more easily recycled at scale many years in the future once they reach the end of their useful lives in vehicles.”
The SUSMAGPRO project ended in 2023 and Moule reveals that, towards the end, its partners had achieved a major milestone: “Recycled magnets produced from secondary material via the patented hydrogen-processing of magnet scrap (HPMS) approach, developed by the University of Birmingham, were tested in rotors produced by ZF. The performance of these recycled magnets was nearly identical to that of virgin materials, demonstrating the feasibility of large-scale rare earth element recycling.”
And Moule reports that the insights gained by ZF designers from the project, primarily around the magnets’ improved recyclability, “are being incorporated into the designs of new ZF motors – which in turn supports our sustainability strategy.”
POLES APART
Although well known for its automotive products, ZF manufactures motors for a large, diverse range of industries, all of which rely on rare earth metals. And the company has a dual focus in this sustainability work: both in the technology involved in putting recycled materials to work and in how to design its own motors so they can be more easily recycled. Which of those two areas is the most important to Moule? “Well, it’s really a single focus,” he asserts. “It’s not possible to separate the two goals of using recycled materials and having motors that are more easily recyclable; they support each other. As more products are recycled, there will be a greater amount of recycled material available for use in motors.”
Moule explains that if the properties of recycled magnets differ from those obtained from virgin material, then design changes may be necessary to enable the use of that increasing supply of recycled material. “Conversely, if motors are more easily recyclable to allow magnets to be more easily recycled – either through mechanical changes allowing easier access to the magnets, or elimination of sources of contamination that may cause degradation in the magnet properties – then there will be more recycled magnets available,” he points out.
Ultimately, Moule says, “By understanding the recycling process, we can make changes to the designs that will improve the efficiency and yield of the recycling process.”
DESIGN FOR LIFE
Successfully juggling various requirements is key to progress here. “Design engineers and recycling engineers frequently have different perspectives on a solution,” Moule observes. “A design engineer will often think in terms of having the smallest, lightest, most appropriate materials to fulfil a function. A recycling engineer is looking to have only materials compatible with a recycling process, not wanting anything present that will contaminate a process. A design engineer focuses on one unit and has lots of detailed data in regard to its make-up. A recycling engineer, presented with that same part in years to come will likely have it included in a mix of parts to process – and have much less detailed information to hand. A design engineer is often thinking about how to make millions of parts in the same place, whereas the recycling engineer is looking to process tonnes of material that has come from many different places.”
Rather than regarding these differing aims as a source of conflict, Moule reports that, “By understanding the various perspectives and considering a whole life cycle rather than just one aspect, our engineers are now able to design and manufacture products that are far more sustainable.”
This collaborative approach is reflected in the engineering expertise that ZF is relying on for this cross-disciplinary R&D work. “We have a range of people involved – from those holding a PhD with years of experience, through to those who have left school much more recently and are currently studying,” details Moule. “The principal skills are those of magnet and motor experts combined. However, the additional skills of the prototype engineers bring added value.”
Expanding on the firm’s in-house expertise, Moule describes how ZF in the UK has a long-established magnetic materials laboratory capable of characterising permanent magnets and soft magnetic materials such as electrical steels. “This unique facility is used not only for understanding the behaviour of magnetic components in our own products but is also offered as a service to external customers.
“During permanent magnet tests we can investigate their behaviour when they are subjected to magnetic fields and temperatures that may demagnetise them, such as those within an electric motor operating at high torque.”
Moule mentions that permanent magnets, such as NdFeB or ferrites, are also used in linear actuators, sensors and electronic components: “ZF engineers are particularly active in assessing options for the use of recycled magnets in motors and sensors,” he says. “Our motor designers are interested in the properties that are achieved by recycled magnets and are well able to determine the impact of these properties on the performance of a motor. They can take the magnet characterisation data obtained from our magnetic materials laboratory and use it in finite element electromagnetic simulations to predict motor performance.”
Following the simulation work, Moule explains that, “Our prototype laboratories assemble motors and sensors for testing using recycled magnets. This allows us to gain not only theoretical but practical confidence in the resulting tests.”
Moving from testing to real-world applications, Moule confirms that insights gained from both the SUSMAGPRO project and ZF’s own development work are being comprehensively applied. “One of the less tangible and harder to measure impacts has been the greater awareness of sustainability amongst the design engineers,” he comments. “It’s been quite subtle: design engineers have started work on a project then stopped and said to a colleague, ‘is this going to be a good idea for the future – it’s OK for now but how is it for sustainability?’ And this wouldn’t have happened before we adopted the more holistic approach to design.”
