Carrs Welding and BIC Partner on Soni-Laser Project for EVs

Carrs Welding and BIC partner on Soni-Laser project for the electric vehicle market

Soni-Laser: Ultrasonic assisted laser welding for high volume assembly of automotive battery packs, is a collaborative project between TWI Industrial Member company Carrs Welding Technologies Limited and the Brunel Innovation Centre.

Carrs Welding was started in the early 90s repairing moulds and press tools for the automotive industry, following which it began laser welding in 1998. Since then, through continuous investment in new technology, the company has grown to be a market leader in precision laser welding. Today, it services more than 350 customers, ranging from one man engineering companies to international aerospace manufacturers, while still supporting the tooling industry.

Brunel Innovation Centre (BIC) is a partnership between TWI and Brunel University London, established in 2009. It undertakes research and development (R&D), in conjunction with industrial partners, based on projects that span national and international platforms. BIC’s areas of knowledge and expertise include power ultrasonics, smart non-destructive testing (NDT), active structural health monitoring (SHM), sensors, structural integrity assessment, machine learning and more.

TWI’s Collaborative Projects programme is designed to support new product, system, process or service development, at Technology Readiness Levels (TRLs) 1-7, through the securing of competitively won public funding from European programmes such as Horizon Europe and Government bodies such as Innovate UK.

The process starts with a unique idea or concept that is developed into a funding proposal, by a specifically assembled consortium of like-minded partners who have complementary skills and experience. TWI’s Technology Innovation Management (TIM) team, which is part of the TWI Innovation Network (TWIIN), takes the lead on the Collaborative Projects programme, working with TWI’s Technology Sections and Innovation Centres, and UK and European SMEs, to identify suitable grant funding ‘calls’, create project consortia, build ideas and concepts into competitive proposals, and submit the final bid documents for consideration.

TWI Industrial Members and TWIIN Members have the opportunity to join project consortia and apply for public funding as part of their membership services. This collaborative approach to technology development enables all parties to maximise their potential for innovation through shared objectives and interests.

Objective

Soni-Laser aims to find the ‘sweet spot’ of welding process optimisation for the production of connections between battery cells, in the types of battery most commonly used in electric vehicles (EVs). In order to introduce the new process developed within the project to industry, the partners plan to weld some battery cells and test them as a battery pack, at a Soni-Laser Open Day planned for May 2023.

Approach

The Soni-Laser project is a follow-on concept from the earlier UltraMat project, also between Carrs Welding and BIC together with six other consortium partners, which aimed to develop a novel, generic technology for the materials processing of fluid and semi fluid phases that is widespread in manufacturing. Potential applications for UltraMat included the welding and adhesive joining of components, and the production of bulk composite components in traditional and powder metallurgy (PM) hot isostatic pressing (HIP).

Winning the public funding to enable Soni-Laser, the consortium for which comprises project lead Carrs Welding and BIC, was achieved with the assistance of the TIM team who were instrumental in the concept development and proposal writing for the project, and submitted the final proposal to the appropriate funding call.

Consequently, the Soni-Laser project was successful in winning grant funding from Innovate UK to investigate the use of ultrasonic waves to improve the laser welding process in automotive, inter-battery connections. The project runs from February 2022 to July 2023.

Industry Relevance

EV sales will reach 44 million units per year by 2030, and while Asia remains the production stronghold, Europe is expanding its production rapidly. Therefore, there is a recognised need to increase the number of battery packs being manufactured in order to meet demand in the UK and Europe.

Laser welding has emerged as the optimal welding technique for accelerating EV battery pack manufacture because it is 4-5 times faster than current welding processes. However, before laser welding can be adopted for this application, there are challenges to overcome.

To deliver the required power and capacity, a standard battery pack consists of hundreds, even thousands, of connected individual cells. This creates several metallurgical challenges when making the required joints, including the joining together of multiple dissimilar materials of varying thicknesses.

Solutions

Soni-Laser will address these by introducing a power ultrasonic vibration treatment (PUVT) into the laser welding process for EV batteries, designed to improve the integrity and quality of welds (Figure 1). The result will be to non-invasively control and modify the microstructure between battery joints during post-weld solidification, i.e., the transformation of the molten weld metal from liquid to solid state, which occurs due to loss of heat from the weld pool.

Ultrasonic excitation (vibration), via transducers, will be used to minimise the formation of undesirable intermetallics and precipitates. The application of vibrations during the laser welding of dissimilar metals, such as aluminium, nickel and copper, will serve to control the shape of the intermetallic compounds during solidification, and lead to a reduction in, or avoidance of, the generation of defects that can severely limit the mechanical properties of welded joints (Figure 2).

Overall, Soni-Laser will contribute to accelerating the production process for EV battery packs.

Carrs Welding’s role on the project is to trial various material combinations commonly found in the EV battery industry, and research what the effects are of applying ultrasonic waves during the welding process.

BIC’s role is to configure a contactless means of delivering the ultrasound waves. This includes leading on the hardware development for the new treatment through optimised application of low frequency, ultrasonic vibration, and the deployment of computational models for process control, as well as advising on designs for both the test sample and the overall system.

Benefits and Conclusion

Soni-Laser is expected to deliver the following advancements in EV battery pack production in the automotive sector:

A reduction in porosity and residual stresses of 25%
A 10% improvement in the mechanical properties of the battery weld due to grain refinement and phase distribution
A decrease in bulk intermetallics of 30% due to lower viscosity, with higher diffusion of materials within the molten pool obtained
At least a 50% increase in laser welding speed, enabling a 10-15% improvement in total battery productivity

The pressure for EV batteries to be more durable, sustainable and efficient is at an all-time high due to the planned UK Government ban on the sale of new, conventional, petrol and diesel cars and vans from 2030, and the similar EU ban effective from 2035, although the latter may give an extension to smaller manufacturers.

Therefore, the new ultrasound technology being developed in Soni-Laser is expected to be of great interest and relevance to the automotive industry, as are the findings of the project which have the potential to influence laser welding procedures in battery packs in other sectors, such as communications infrastructure and pipeline monitoring.

Soni-Laser has secured funding from Innovate UK for collaborative R&D under grant agreement no. 10018077.

Figure 1. Integration of ultrasonic system into the laser welding machine.

Figure 2. Applying a contactless vibration to the molten pool area during the welding.

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