Die Casting Offers Alternatives for Copper Coils
8/25/2022 Technology & Processes Interview

Die Casting Offers Alternatives for Copper Coils

The three-way alliance of the Fraunhofer Institute for Manufacturing Technology and Applied Materials IFAM, the die casting foundry Ketterer, and the motor manufacturer Heinzmann has developed cast aluminum coils for electric motors for the first time. At EUROGUSS, they will present the demonstrator motor manufactured for the first time under series production conditions.

European Flag A three-party alliance is showing Germany a perspective on wound copper coils in the form of cast aluminum coils. This is intended to benefit electromobility in particular. At EUROGUSS 2022, they have presented the demonstrator motor manufactured for the first time under series production conditions. / Source: Corinna Robertz
The Fraunhofer Institute for Manufacturing Technology and Applied Materials IFAM has developed a process for producing aluminum coils by die casting. Compared to their wound copper counterparts, this should increase the continuous output of electrical machines and reduce weight by at least forty percent in terms of the coil. The cast coils are characterized by a flat conductor arrangement, which leads to better utilization of the available installation space. Although the cast aluminum coils have a higher electrical resistance in relation to the material compared to the wound copper coils, the larger cross-section results in a lower resistance in relation to the entire coil. With better connection to the laminated core and more favorable utilization of the installation space, according to Fraunhofer IFAM this results in better thermal and electromagnetic behavior. The larger cross-section of the cast coil compared to the wound coil fully compensates for the poorer conductance of aluminum compared to copper.  

The concept has now been implemented and produced in series for the first time by the die casting foundry Ketterer and engine manufacturer Heinzmann. “A research project has turned into an industrial application,” says Franz-Josef Wöstmann, head of the Early Technology Recognition and Utilization department at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM. “This shows that it can be transferred to series production!”  

By simply equipping the motors with die-cast coils, it may be possible to partially replace winding technologies. According to Peter Mérimèche, managing director of Heinzmann, however, the existing cost advantage and technical benefits remain the main argument for market acceptance. Mérimèche said his company has developed a new generation of wheel hub motors that will use the aluminum coils. The PRA230 wheel hub motor can be used for mobile applications such as agricultural applications or light vehicles in the L7 category, as well as AGVs, he explained.  

At EUROGUSS, Franz-Josef Wöstmann from Fraunhofer IFAM and Holger Knobloch, Head of Technology/Sales and authorized representative of Ketterer Druckguss, presented the demonstrator engine to the public for the first time. 

Holger Knobloch: This is a world first. No other application in the world in the electric motor sector with aluminum coils cast by die casting has our production progress. Of course, this also unlocks enormous potential for Germany as an aluminum die casting location in the future. Despite the current crises, despite the discussion about the energy intensity of the industry, our aim is to show that highly innovative areas can be developed with aluminum die casting. This also holds real prospects for Germany as a manufacturing location.  

Franz-Josef Wöstmann: In the past, motor designs were always thought of in terms of wires. And the wires used were always copper because on the one hand the conductivity of copper is very good and on the other hand because the formability for winding copper is very good. Approaches with aluminum have generally failed because aluminum is more difficult to form. In addition, a wound aluminum wire has poorer conductivity. But our die casting process allows us to completely adapt the geometry of the winding to the installation space. This makes the cross-section larger. A cast aluminum coil thus has a lower electrical resistance in relation to the coil. This means that only casting technology can make the use of aluminum economically and technically viable. Only here can we realize a variable cross-section with different geometries. The motor then has greater efficiency than with copper, is lighter, cheaper, and more environmentally friendly.  

Knobloch: What we have implemented here together with Fraunhofer IFAM and Heinzmann is not entirely trivial. If you asked ten die casters whether this coil could be cast in aluminum die casting in a cold chamber, nine out of ten would answer in the negative and one would not be sure. We are moving here within the limits of what is feasible in aluminum die casting. This starts with the wall thickness: The textbook says that aluminum die casting starts from 1 - 1.5 millimeters upwards. This means that our casting lengths are theoretically not feasible at all. And the 3D geometry that we reproduce with it is certainly not.  

What is the argument in favor of substituting aluminum for copper? 

Knobloch:
Compared to copper, there is a clear advantage in the extraction of aluminum in terms of energy use. Aluminum has a lower melting point than copper and therefore a better CO₂ balance. We also have a weight advantage of aluminum over copper. In addition, although I don’t know the current prices, copper costs about three times more than aluminum in terms of weight. And at the end of the day, recycling copper coils with the insulation used is very problematic. The insulation has to be removed first, including all the toxins that are created in the process. However, if the motor with aluminum coils needs to be appropriately recycled after decades of use, the coil can also be dismantled and fed into the recycling loop. 

Wöstmann: Aluminum is one of the most common elements on our planet. That’s a big difference from copper, because copper is primarily mined in Chile and China and supplied from there. We have a massive dependence on these two countries in particular. At the same time, copper resources are gradually running out. This means that while on the one hand we have a shortage due to pure availability, on the other hand we are seeing a much higher demand for copper due to the increase in prosperity, the use of electric machines, and the demand for more electric drives. As such, copper is expected to continue to be used as an essential component in electric drives. As a result, copper will become a strategic material within a very short period of time.  

They were brought together by a press report from IFAM about the possibilities of using coils cast in aluminum for electric motors. Why like this and not some other way? 

Knobloch: What is being done by policymakers to promote innovation? There were the so-called research projects from the Federal Ministry of Research and Technology. Yet the secret lies far more in consolidating knowledge. And for that, you always need a driving force as well as face-to-face communication. You have to be able to trust your partners. A three-way partnership is even more complicated to manage than a marriage. All three sides need to feel like they are part of a win-win-win situation. The e-motor presented is the result of a joint partnership effort. 

Wöstmann: Here, people have come together who understand each other, and, at the same time, they are people who display something that has sadly been lost in Germany over the last twenty years: a little bit of daring and entrepreneurial spirit. No more leaning back and demanding that new topics be served up on a silver platter free of charge. Unfortunately, that is now the German mentality.
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Authors

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Corinna Robertz