Changing requirements for fastenings in the evolving EV market
Author : Sven Brehler | Director of Engineering | TR Fastenings
01 November 2021
TR Fastenings_Changing requirements for fastenings in the evolving EV market
Rapid growth in the electric vehicle (EV) market, including associated products such as batteries & charging units, is demanding a different approach – accelerating time-to-market, compared to traditional vehicle production. ‘Fast to market’ is the byword as companies enter the market with a mindset we are far more used to seeing in the electronics & high-tech sectors.
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In conjunction with this comes technical challenges, as new products are developed, requiring different solutions that meet stringent requirements, particularly in the battery casings. Here, Sven Brehler, Director of Engineering at specialist in the design, engineering, manufacture & distribution of industrial fastenings, TR Fastenings outlines the role of fasteners throughout EV applications…
TR is actively working with organisations involved across the design, manufacture and development of electric vehicles (EVs), battery pack modules (EVBs or electric-vehicle batteries) and EV charging units for both commercial and residential use. The electrical, electronic and mechanical systems throughout all require a range of fasteners, including screws, bolts, clips, washers, bushings, gaskets, as well as surface- and PCB-mount and cable management fastenings.
Meeting the EV battery challenge
The latest ‘skateboard’ chassis platform forms the basis for many new EV designs, including people movers, delivery vehicles and buses. This new manufacturing concept cuts down on complexity, providing a common platform that can be easily scaled across different vehicles.
Modular, self-contained skateboard designs can form the basis of multiple vehicles, with minimum requirement for re-design. A great deal of focus is placed on the load-bearing structure, which integrates the battery pack and drive train. Interchangeability of various modules within this design allows the skateboard, and therefore new vehicle models, to stay at the cutting edge of battery and drive train innovation.
The interior of vehicles is changing dramatically too, particularly within the cockpit. We are seeing many new concept designs, which all require fresh thinking in terms of fastener applications. Fasteners are also now increasingly being used as a visual design feature, which you will see in new models – for instance, with the manufacturer’s name stamped into the head. These need to be aesthetically pleasing, and finish quality is critical for longevity. The exponential rise of in-car technology, such as connectivity with 5G networks and large IP (instrument panel) console screens, and concept seating are challenging conventional fixings, especially into composite materials.
Correct fastener design and selection is key to the success of the modularity and design life of skateboard platforms, by strategically selecting serviceable fasteners where modules or elements will require maintenance or potential updating in future. Designing in reversible joining – bolt and nuts – does allow for a more economical (and potentially automated) retrieval of undamaged individual components. The right selection of fasteners can also help meet eco-design criteria. This retains the maximum value at the end of a vehicle’s life and plays a part in the preparation of extended producer responsibility regulations, where manufacturers have to consider their own final responsibility for disposal of their manufactured products.
TR Fastenings group shot
Where appropriate, non-serviceable joints, such as moulded inserts and self-clinching products, can be designed in. TR’s engineering expertise has supported many companies in optimising designs, considering ease of manufacturing, product cost and, where possible, lightweighting and the use of mixed materials.
One of the best illustrations of this has been the increasing use of composites in assemblies. Therefore, the need for products such as compression limiters, which are designed to take the fastener load and provide a structural through hole, without risk of delamination, creep or stress cracking. Generally, these are produced in steel, stainless steel, brass and aluminium, and are designed and manufactured to exact specifications. There may also be a need for electromagnetic shielding, requiring electrically conductive fasteners.
The demands of the circular economy and meeting the recyclability demands of products is also a strong consideration in many new designs. At the end of the economic life of either the vehicle or mobile battery, there is usually now an option to re-use or repurpose. The importance of the highest number of components capable of being recycled is a key factor – and fastenings are no exception. Ease of disassembly for battery pack removal is an additional factor. Most of these challenges can be overcome, or their effects reduced, with the right engineering choices. TR can provide support and delivery of suitable products.
Rationalisation and standardisation of fixing methods and drive systems, such as hex lobular fasteners, which have a similar torque capacity during assembly and disassembly, can support automation. TR engineers can also share their experience in fastener positioning for easy access, or help to select suitable materials or coatings to avoid fastener damage through galvanic corrosion.
Often connectors, charging pins and busbar components are not considered as fastener products – but they are part of a holistic product offering as their mating components. It is important that the entire assembly is viewed in the round to enable a better understanding of requirements. We have the capability to deliver thermal and electrically conductive products in copper, aluminium or brass. These can be tin, or silver plated – and if required, compliant with technical cleanliness requirements. We can also challenge designs, originally machined, to be partially or completely cold formed, increasing cost effectiveness and reducing the carbon footprint of the product.
At the end of the economic life of either the vehicle or mobile battery, there is the option to re-use or repurpose. Unfortunately, not all battery technologies lend themselves to repurposing, due to poor cycling performance. In other cases, the limitations are due to few available disassembly facilities, or lack of batteries themselves to consider repurposing on a commercial scale. So, the consideration of assembly of new materials and their recyclability make for new challenges in this fast paced growth opportunity.
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