A licence to print... Coils

Chris Callander finds out how a German company is transforming the production of motor coils, and explores what impact that may have on the motor repair sector.

Additive Drives was born after two of its cofounders, Dr. Jacob Jung and Alex Helm, realised their expertise in the automotive sector and additive manufacturing, respectively, could be brought together to solve a challenge presented by the fast-growing demand for traction motors.

It is well recognised that it is challenging to create working prototypes of motors for automotive applications. Setting up for prototyping or sampling motors often requires a lot of tooling, particularly when it comes to hairpin windings and large copper conductors. Plus, designs are restricted in terms of their geometry by conventional coil manufacturing.

But Jacob and Alex recognised that if they could find a way to 3D print coils and, in doing so, benefit from optimised designs, they could overcome the limitations and speed up the production of prototypes, while in many cases doing so more cost-effectively than conventional methods.

Officially launched in July 2020, Additive Drives, which is based in Dresden, Germany, primarily works with high-performance applications such as motors for racing and aviation applications, producing short- to medium-run production batches and fastturnaround prototypes.

Coils are printed using selective laser melting, otherwise known as powder bed fusion. This additive manufacturing process uses high-power lasers to melt metal powders and fuse them together to form the desired solid mass. However, existing 3D printing machinery had to be adapted by the team at Additive Drives to make it suitable to work with the oxygen-free copper powder required to manufacture motor coils.

MORE THAN SIMPLY PRINTING For Additive Drives, additive manufacturing is just the enabler that makes a range of benefits possible. As well as accelerated development times, additive coil production can deliver improvements in weight, volume, and performance.

Alongside printing clients' coils to their design, Additive Drives also offers design optimisation, utilising the benefits available through 3D printing.

Based on electromagnetic and thermal simulation of a coil's CAD design, the Additive Drives team can save up to 40% of the copper mass, meaning only the remaining 60% needs to be printed. This makes it possible to identify areas where the copper cross-section can be reduced as it is not critical – such as in the connections – potentially reducing size,

The design of bending weight and cost. Equally, radiuses can be optimised in areas where with insulation in mind. the analysis identifies hot spots, the copper crosssection can be increased to compensate – meaning greater performance and reliability. Creating the geometry through 3D printing allows coil geometries that are more complex than is

SIZE MATTERS

About 80% of the motor coils produced by Additive Drives have an outer diameter of less than 250mm and are typically for traction motors used in electric vehicles. If coils are printed in a single part, the equipment limits their outer diameter to around 350mm. But, if a coil is printed in sections, greater sizes are achievable.

possible with traditional methods. This allows insulation to be designed in a different way to conventionally manufactured coils. For example, the design of bending radiuses can be optimised with insulation in mind. While in hairpin windings, for example, air gaps can be far more accurately managed. In addition, the integration of connection technology can be optimised, and end turn lengths can be reduced.

MOTOR REPAIR POTENTIAL Currently, Additive Drives' focus is on designing and developing coils for use by motor OEMs. But the technology and approach can, in theory, be used to produce replacement coils as part of motor repair or overhaul. The technology can also be used to create coils that are in part traditionally wire wound and part 3D printed. This allows 3D printing's benefits when it comes to complex shapes as part of the connection technology to be integrated with a traditional approach.

In reality, though, it will be some time before repair shops are routinely using 3D printing to create replacement motor coils. While series production of coils can be more cost-effective than other production methods, the cost and complexity of 3D printing coils mean it is not really viable for one-off replacements in most cases. But, as motors become more complex and the cost of the technology reduces, there will come a time when this approach is far more viable and, in turn, common. TIMES-CIRCLE

www.additive-drives.de