26 May 2021
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Lightening the load: the benefits of vacuum impregnation for electric vehicle manufacture

The shift to electrification in the automotive industry is accelerating, fuelled by more stringent emission regulations, access restrictions in cities and advancing EV technologies. However, sustainability goes beyond just vehicle efficiency and into considerations around materials and production processes. Vacuum impregnation can contribute positively in each of these areas. John Holmes, applications sales director (impregnation) at Ultraseal International explains how.

Sales of battery electric and hybrid vehicles are growing, driven by an increase in consumer demand and the rapidly increasing availability of EV-models. Policymakers are pushing the auto market towards lower emissions. The UK has set a new goal of banning sales of conventional fossil fuel vehicle by 2030, and only allowing zero-emission vehicles from 2035.

Vehicle manufacturers are understandably fully focused on sustainability. This focus takes in many aspects beyond just the way their vehicles are powered. It’s about making all of their vehicles more efficient – and that means their internal combustion engines too. It also means looking at ways to increase the efficiencies within their operations, including the supply-chain and production. In each of these areas, vacuum impregnation, a long-accepted technology in the automotive sector, has an increasing role to play.

One of the main ways to lightweight vehicles is by using structural die cast components and replacing heavier metals such as steel with far lighter alternatives, especially aluminum. This can be used on a wide range of components, including drive and powertrain. The net result is that battery range is greater, and vehicles go further.

However, during the die casting process, microscopic holes are formed in the metal, resulting in tiny imperfections. This is known as porosity. Often this porosity has little or no bearing on the performance of the component, but it can cause structural weaknesses. More commonly, it forms leak paths which could affect the functionality of the component, especially in applications that need to be pressure- or fluid-tight. Porosity is a consequence of die casting and is more likely to be an issue with thinner-walled castings.

So, while die-cast components offer big opportunities to reduce weight, the potential risks need to be managed effectively. This has always been the case for internal combustion engines. In hybrid and electric vehicles, it’s especially so for such critical components as electronics, the powertrain or complex cooling systems.

For the automotive industry, vacuum impregnation is the accepted and OEM approved method for solving the problems of porosity in metal castings, sintered metal parts and electrical components. It vastly reduces or eliminates the risk, ensuring the viability and performance of critical components.

Although it uses specialist equipment, the process is relatively straightforward, and many manufacturers install and operate the technology on site. Components are placed in an autoclave, a vacuum is applied then after a period of time the components are immersed in sealant. The vacuum is used to draw the sealant into the micro-porosities and leak paths. This is then effectively sealed in a hot-cure process which turns the liquid into a chemically- and thermally-resistant polymer. The result is a more reliable component, whatever the metal or its weight.

Vacuum impregnation therefore improves the performance of components and helps contribute to lighter and more efficient vehicles. This is the key contribution to manufacturers in their search for sustainability, but it’s not the only one.

Vacuum impregnation also makes a significant difference to operational efficiency in terms of reducing scrap and waste.

State-of-the-art equipment, such as that provided by Ultraseal International, a Quaker Houghton company, uses recyclable sealants to improve its environmental footprint. Rather than being flushed away, these are collected from the wash tank and processed in a special sealant recycling system. In addition to using less sealant, the process also uses considerably less water.

There’s also no need to change the wash-water tank. These benefits reduce cost and downtime while contributing to more sustainable production efficiency.

Vacuum impregnation requires dedicated equipment, but the benefits it delivers are considerable. Ultraseal has a wide variety of equipment and can tailor a solution to suit the customers’ requirements, which could be delivered on or off site.

Where high volumes are required, the process can be automated, reducing labour costs and operator involvement even further.

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Ultraseal International

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