Cold forming the future of automotive

Cold forming is now being used to manufacture power connectors that optimise the performance of electric vehicle charging units. Produced from oxygen-free, high conductivity materials, power connectors produced using the process are vital to ensure there are no power losses in this application, says Mark Jennings, engineering director at Dawson Shanahan.

The requirement for highly complex component parts to be manufactured to exacting tolerances is becoming a critical factor for today's sophisticated high-tech equipment used in the automotive industry. This has pushed the boundaries of processes such as cold forming, resulting in precision-built parts with a fine level of accuracy that can be measured in terms of microns. It has also broadened the potential use of cold formed components for relatively new technologies that are becoming mainstream, such as electric vehicles.

Traditionally, the cold forming process has been associated with manufacturing simple components such as screws and bolts in vast quantities quickly and efficiently, while many larger or complex parts are manufactured using conventional processes such as machining and forging. Although the latter processes have their advantages, they can be expensive, time consuming and require multiple process stages to produce precision components with high definition surface finishes. Additionally, machining operations are generally extremely wasteful in that they generate large volumes of scrap as parts are cut or milled from solid billets of material.

Although the high cost of materials and energy consumption is leading engineers and designers to consider cold forming as a commercially viable alternative, it is the potential to produce extremely high quality components with superior mechanical characteristics to ultra-fine micron accuracy that is attracting the electric vehicle market.

Bring on the benefits

Precision cold forming is capable of delivering precision engineered parts with up to 80% less scrap than other machining processes. Coupled with faster leadtimes, better surface finish and improved mechanical characteristics, precision cold forming offers an opportunity for manufacturers to take advantage of enhanced component quality while also reducing costs.

Performed at ambient temperatures, cold forming is a far quicker process than many competing techniques – which means that components can be made to order quickly, cutting leadtimes and the need to store high volumes of spare parts onsite. Aside from tangible cost savings, cold forming makes for superior quality products by plasticising metals along their grain boundaries rather than cutting across, thus producing parts with low levels of stress deformation and high levels of mechanical integrity, resulting in enhanced performance and reliability.

Furthermore, cold forming offers outstanding levels of definition, even on parts with complex contours. Typically, dimensional tolerances can be to within ±2µm with the added benefit of fine surface finishes, which in many cases require no further machining or polishing.

Additionally, parts undergo work hardening during the cold forming process, improving their machinability and durability still further. Work hardening reforms the structure of the metal in a way that prevents further dislocations, resulting in a stronger component. As this increase in strength is comparable to that of heat treating, it can be more cost-effective to cold work a less costly and weaker metal than to hot work a more expensive metal, particularly where a precision finish is required.

The cold forming process also makes it possible to produce component parts with a superior finish, both internally and on the surface. Accurate internal profiles and complex external profiles are possible, enabling precision parts to be manufactured – which can have a significant impact on the performance of the equipment in which they are used. Furthermore, there is almost no limit to the shape, size or complexity of the metal components that can be produced using cold forming. Simple or highly complex cold formed and finished machined components can be produced for a diverse range of applications.

Electric vehicle evolution

The fact that cold forming offers the huge list of benefits described above is vital in an industry such as electric vehicle manufacture that is still to an extent proving itself to the automotive market.

We are now seeing increasing numbers of electric vehicles on our roads. According to the SMMT (Society of Motor Manufacturers and Traders), electric vehicle registrations in 2014 were up 10% on the previous year to a figure of almost 1.3 million. But although electric transport brings hope for enhanced future sustainability it also carries with it challenges for the engineering industry, as each advance in one stage of the power transmission chain requires others alongside to match it.

The best current lithium-ion battery, which employs metal oxides in the positive electrode, cannot provide much more than 100 miles of service – not a viable solution for widespread take-up. And then there are charging stations to consider. As plug-in electric vehicle ownership continues to expand, so does the need for charging stations with fast charging capabilities. In addition to on-street facilities provided by electric utility companies, there are now mobile charging stations providing a range of special connectors to accommodate a variety of vehicles. So, enhancements to even the smallest components are required to establish the electric car as a serious competitor to petrol powered transport.

Optimising powertrain efficiency is an excellent way to increase electric vehicle mileage and reduce energy consumption while maintaining performance levels and there has therefore been considerable innovation in this field. For example, electric vehicle motors are engineered to run at very high speeds to increase efficiency and power density.

Recent advances in the manufacture of power connector technology are enabling designers to extract greater efficiency from motors and power trains. Power connectors are widely used in electric vehicles, for example in charging units and the motors used to drive each wheel. The focus for manufacturers is to find ways of improving the efficiency of power connectors to minimise power losses while reducing weight and cost.

Cut your losses

One option is to engineer connectors using precision cold forming which enhances part quality and significantly cuts metal waste. At Dawson Shanahan, we have used our renowned precision cold forming expertise to manufacture power connectors that optimise the performance of electric vehicle charging units. Our high power connectors are generally produced from oxygen-free, high conductivity materials that are vital to ensure there are no power losses in this application.

With outstanding levels of accuracy and efficiency, cold forming can produce extremely strong, lightweight components with excellent surface finishes in a single production operation. This versatile and cost effective method of manufacture is also meeting the requirements for quality and precision set out in today's industry standards. In fact, the finished parts display no surface scaling and superior definition and finish.

In addition to the increase in component quality brought by cold forming, the cost savings for high volume production runs are significant. The cold forming method is ideal for industries such as automotive, aerospace, and alternative energy, indeed, anywhere where high integrity parts are a must and reliability is critical.

Dawson Shanahan
www.dawson-shanahan.co.uk