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FEMM Hub Focus on Cross-cutting theme 1 - Sustainable manufacturing of electrical machine components for the circular economy

11 November 2021

With the world focused on a route to net zero, sustainability should be at the core of future manufacturing processes.

Within the Future Electrical Machine Manufacture Hub (FEMM, sustainability is a key cross-cutting theme that aims to engage academia and industry alike, to identify ways to embed reuse and remanufacture in the design of electrical machine components.

How can this be achieved?

By viewing the integration of sustainability as a fundamental part of manufacturing processes, it becomes clear that work streams, whether technical or supply chain focused, are linked together by an underlying appreciation that it contributes to the achievement of project objectives. One way to do this is to look at the building of electrical machines more holistically, by looking at ‘families’ of components rather than individual items. 

By making small adjustments it is possible to reduce wastage as starting material is processed in the most efficient method for maximum material utilisation. For example, many near net shape manufacturing processes, such as spinning or hydroforming, use sheet metal as an input material instead of forgings or castings. The use of sheet input instead of bulk preforms ensures better utilisation of material and minimal final machining. Many near net shape forming operations are also conducted at room temperature, negating the need for heating during, or prior to, the manufacturing process, hence reducing energy consumption.

Furthermore, manufacturers currently assemble machines with a focus on cost and robustness with limited consideration of disassembly. Using glue, welding and resins, for example, ensures that components remain fixed and perform to specification during operation, but make it difficult to take apart at the end of the equipment life. 

By considering disassembly at the design stage - modest changes could be introduced which greatly simplify disassembly leading to viable and cost-effective routes to precision repair or remanufacture. Examples of this approach in electrical machines can be illustrated by considering failures due to coil insulation.

The so-called ‘re-wind’ of electrical machines is a long-established and still vibrant business in industrial electrical machines and involves stripping out winding from the stator core, often through the application large amounts of heat and mechanical force. The methods necessarily adopted to remove the damaged portion of the winding means that the full winding is often replaced and the stator core suffers some degradation from the heat applied and also requires time-consuming cleaning to remove residual resin deposits. 

Traditional approaches to machine re-wind make an important contribution to machine repair and re-use in many industrial machines but arguably lacks the precision to deliver a minimum material replacement. Coils are components of a machine which could be replaced at a very localised level if it was possible disassemble the machine, but many current designs do not allow for this which leads to either a major overhaul of the machine such as a full rewind of a stator in which only one coil out of many is damaged or, in the worst case, the scrapping of the entire machine which could have 95% of its components still in good condition. 

One of the challenges for the FEMM hub going forward will be to find solutions which increase the speed, precision and reliability of rewind activities.

Routine maintenance and replacement of parts in high value equipment is standard practice across many sectors. The higher the value, the more cost effective it becomes to replace components on machines. 

These machines have typically been those which rely on finite virgin resources to manufacture. In the past, a large proportion of electric machines have been much lower value, reducing the incentive to replace parts in the same way. However, with FEMM Hub research seeking to introduce innovative processes, materials and monitoring of high value electric machines- as well as the push for wider electrification of transport and energy sectors- this balance is soon to change. 

If electrification is to be used widely in aerospace, for example, the push for remanufacture of non-compromised components will make a key contribution to reducing the carbon footprint of the industry. This comes not only from reducing waste directly, but also brings into play the wider issues of increased carbon footprint transporting mined goods for manufacture around the world.

The role of this cross-cutting theme is to integrate with all grand challenges within the FEMM Hub and embed sustainability into all the streams of research from the very beginning, thus allowing for small changes to be made to designs which will lead to massive improvements in the final product. One way this is being done is with Grand Challenge 2.3 which is looking at developing an automated cell for the manufacture and assembly of stator laminations and coil windings. 

If sustainability is not considered for this stream of work, a highly automated cell will still be developed, which will improve the manufacturing capabilities for high value electrical machines within the UK, but the issue of disassembly and repair will remain unanswered. If, however, we make the repair of machines an integral part of the discussion from the start, then not only will the manufacturing cell be achieved, but the learning outcomes from this part of the project could be implemented to ensure the same technological advances are utilised to solve disassembly challenges. This joined up approach will require minimal additional effort to ensure maximum impact in a sustainable future for electrical machines.

The reuse and remanufacture of items needs to be more joined up across the industries. In aerospace, for example, where the highest part integrity is required, the reuse of components may not be a viable option, but these parts could be efficiently reused for a second-life in other power conversion sectors. 

Collaboration across sectors is not traditionally strong, but the High Value Manufacturing Catapult centres are playing an increasingly important role in enabling a more joined-up approach. This could produce a more sustainable supply chain which would have wider significance. At the electrical machines level, changes will be implemented moving forwards, with the change of materials and assembly methods, but the biggest change could come from the linkage of companies and sectors which have not traditionally collaborated.

The FEMM Hub has spoken to our industry partners and can identify a keen appetite to be more sustainable through carbon accounting and life cycle assessment, but how to start their journey can be more difficult for some to identify. Industry need to be open to the changes that are inevitable, and research groups such as FEMM Hub, together with the catapult centres need to make it easy for them to be brought along with those changes. Opening the conversation more widely to encourage supply chains to be more sustainable, perhaps through the development of items usable across sectors, demanded by industry may also be a factor.

The immediate focus within FEMM Hub is education within companies, introducing them to the tools and techniques they can use to assess their carbon costs of manufacture. Once they have this starting toolkit in place then the Hub can begin to work with them to redesign the components which are less carbon intensive or have better end of life processing.

We are now at the stage of compiling case studies to show how the reuse or remanufacture of specific parts can make a difference in the carbon cost to the company. Education is also critical to ensure that the advantages associated with remanufactured components are also understood. 

For example, an electrical machine which is taken out of service to be remanufactured can not only maintain previous performance targets, but could even exceed them due to upgrades in power electronics or control software which were not available when the machine was originally put into service.

Renewable Part Ltd (RPL) is a supply chain and refurbishment specialist in the wind energy sector, which focuses on circular economy of wind turbines. RPL provide customers with remanufactured wind turbines which come with a full service history, remanufacturing plan, and five-year warranty. 

All of their turbines also meet the strict safety standards within the wind energy sector. Although RPL do not focus on electrical machines within wind turbines, the success of their approach points towards a more sustainable future for electrical machines in the wind sector.

There needs to be a shift in mind-set when it comes to remanufacture of electrical machines. The cost to disassemble and remanufacture an item may only reduce the cost by 20% over buying new, and end-users perceive that new is better so will pay that higher price. In fact, remanufacture produces parts with the same reliability and lifespan guarantee, and must not to be confused with ‘repaired’ items.

This is key to increasing the take-up, and although a change in attitude is apparent in the next generation of engineers, that realisation needs to be adopted sooner if manufacturers wants to play their part in reducing carbon emissions now.

This cross-cutting theme is led by Dr Jill Miscandlon from the National Manufacturing Institute Scotland (NMIS) at the University of Strathclyde, shown here at COP26. To find out more about FEMM Hub’s circular economy theme contact femmhub@sheffield.ac.uk