Advancing Electric Motor Design Through Additive Manufacturing

In the race to meet the UK Government's target of achieving Net Zero by 2050, Electrification, the movement to use sustainable energy sources to replace fossil fuels, has been identified as a key contributor to decarbonising industry and reducing the impact of climate change. As a result, there is huge industrial demand for high-performance power electronics, machines and drives (PEMD). These technologies are key to lower emissions and improved energy efficiency, resulting in lower energy costs in comparison to the use of fossil fuels.

The Manufacturing Technology Centre (MTC) is part of the High Value Manufacturing (HVM) Catapult, an expansive network of fellow Research Technology Organisations (RTOs) that work together to solve challenges faced by UK manufacturing.

The MTC's capabilities in areas including automation, digital manufacturing, advanced tooling and component manufacturing enable it to develop and prove manufacturing processes and technologies that can become the catalyst for future growth of innovative, world-leading technologies.

One such project taken on by the MTC's electrification team sought to investigate the state of the art to determine current constraints and development opportunities of additive manufacturing for electric motor components.

Additive manufacturing (AM) has been identified as an enabling technology to produce power-dense electric motors in a repeatable and short lead time. Whilst additive manufacturing isn't new, its application for end-use parts and tooling has become more prevalent in recent years and is demonstrating its potential to change the way products are designed and manufactured.

With limited examples of AM in commercially developed products, the MTC's technology experts initiated a project that considered the wider implications of additive manufacturing for electric motors. The aim was to provide recommendations, based on existing limitations, for creating the next generation of electric machines.

PROOF OF CONCEPT

 In the first stage of the project, which became known as Future Electric Motor Systems or FEMS, technology readiness level (TRL) and manufacturing readiness level (MRL) assessments of additive manufacturing for key motor components were conducted. These assessments were combined with learnings from past projects and an analysis of present manufacturing techniques for each component. In doing so, the MTC could identify the current constraints and how, by applying AM, these limitations may be resolved.

To demonstrate the potential benefits of leveraging the capabilities of AM, the cooling method of a commercial motor was reassessed as a result of several iterations of a liquid-cooled motor casing.

From the research, a roadmap to support manufacturers in implementing AM technologies for electric motors was created. And for the project's commercial motor, a redesign of the casing allowed it to produce more power by implementing liquid cooling channels to prevent overheating. In addition, the design freedoms of additive manufacturing enabled a weight saving of 10% and a size reduction of 30% due to component integration.

"Additive manufacturing is complex, but the opportunities for businesses to improve their productivity, efficiency and cost savings – and therefore their competitiveness – are significant. This project has the potential to transform the industry as we know it," commented Dan Walton, Senior Research Engineer at the MTC.

INCREASING PERFORMANCE

In the second stage of the wider project, known as FEMS2, a collaboration between the MTC, its members, and the local supply chain was established to showcase state-of-the-art technologies to support the development of high-performance electric motors. In response to industry's demand for higher-power motors alongside reduced weight, the aim was to design, manufacture and assemble a high power-density electric motor prototype.

The project applied simulation toolsets to generate and optimise the electric motor's electromagnetic, mechanical, and manufacturing design. Computer-Aided Design (CAD) toolsets then allowed MTC designers to reduce the mass of the electric motor product and validate its structure for the calculated loading conditions.

In-house subtractive manufacturing and metrology inspection capabilities were then used to create the first fully-functional electric motor prototype. Critical assessment of all aspects of the design and manufacturing process allowed other design and process recommendations to be made with a view to improving productivity, reducing costs, and de-risking the end-to-end process before the final manufacture of the motor's components was carried out with some aspects supported by the local supply chain.

Assembly of the electric motor was completed within the MTC's flexible manufacturing cell, which uses reconfigurable equipment suitable for the assembly of a range of electric machines. This included automated winding to deliver highly repeatable wire placement, a smart assembly bench which intelligently guides users through the assembly of multi-variant assembly tasks, smart production tools capable of highly repeatable screwing operations with torque feedback to ensure repeatable and validated assembly, and 3D-printed tooling and fixturing which offered a low-cost solution to aiding users in assembly processes. In addition, high-performance additive manufacturing polymers, suitable for low-volume manufacturing of parts that would otherwise require high-cost injection moulding tooling, were employed.

The result of this stage of the project was a power-dense electric motor capable of 18kW mechanical output in a 7kg package.

REDUCING WEIGHT

In the third stage of the project (FEMS3), the team redesigned an MTC-designed motor casing for a lightweight aerospace application. They used additive manufacturing technology to combine three machined components, eight fasteners and three o-rings into a single part. The result was a motor with a mass reduction of more than 65%, with additional benefits seen in the reduction of assembly steps. The team also used high-value design tools and AM manufacturing processes to redesign components in the rotor assembly, allowing four parts made from three materials to be consolidated into a single component, further reducing weight and simplifying assembly.

Commenting on the project, Ollie Hartfield, MTC research engineer and member of the FEMS3 team, said: "The aerospace motor we have developed showcases the potential of additive manufacturing and advanced design tools to manufacture high-performance electric motors. The key benefits include reducing the lifetime environmental impact compared to conventional manufacturing and offering a lighter motor with increased performance and greater ease of assembly."

The success of this project hasn't gone unnoticed, with it recently winning the 2022 3D Pioneers Challenge award – an international design competition for advanced manufacturing technologies.

Electrification presents exciting new opportunities for UK manufacturing. The work of organisations like the MTC and its partners in pushing the boundaries to deliver groundbreaking manufacturing solutions is invaluable.