CABLES & CONNECTORS FEATURE


ALTERNATIVE APPROACH HELPS COMBAT RISING COPPER PRICES


Switching from mill-supplied rods to oxygen-free copper wire – and using a different production process – could help connector manufacturers overcome historic high prices, as Les Reeves from precision engineering company, Dawson Shanahan, explains


C


opper has been a valuable material for many thousands of years, with its earliest


use estimated at around 9,000BC. Rising demand, however, has pushed the price close to its historic high point. The metal is used across many industries –


from power generation to automotive. In modern times, its most valuable property is its high electrical conductivity, with its rising price being driven largely by the move towards electric vehicles (EVs). Copper is used widely in EVs, in components such as the battery, connectors, and in the charging stations that pump energy into the car.


EV DEVELOPMENT The Copper Development Association (CDA) says copper is ‘essential’ to EV technology. While a conventional car might use up to 22.7kg of copper, and a hybrid around 38.5kg, a full electric vehicle uses more than 82kg, it says. The majority of this is used in the battery. This higher demand has propelled copper prices


close to an all-time peak near $8,000 per tonne – and it is still on an upward curve. While the EV industry currently accounts for 1% of copper demand, this may mushroom to around 10% by 2030, say many analysts. It all means that EV car makers will be fighting for limited copper resources. CDA says that the increase in the number of electric vehicles on the road will raise demand for copper by more than 1.7 billion tonnes by 2027. One thing is inescapable: higher copper prices


will lead to more expensive components – raising the cost of the final vehicle.


PRODUCTION VALUES Copper parts and components such as connectors are typically machined from mill-supplied tellurium copper rods or bars. This type of copper


is at the premium end of the price scale. However, like all materials, copper is supplied in a variety of grades, and there is a cheaper alternative: oxygen-free copper wire. This has superior electrical conductivity and chemical purity that is beneficial for EV components – but has a much lower price tag. While copper wire cannot be machined in the


same way as a rod or bar, it can be processed using a technique called cold forming to create parts such as connectors. And, despite its lower price, oxygen-free copper – when processed in this way – can produce better results than conventionally machined tellurium copper in many applications. While the lower price of oxygen-free copper


is an advantage, there are also specific benefits to using cold forming as a technique. For one, much less waste – up to 80% – compared to conventional machining. Rather than starting with a block of copper – and milling a smaller component from it – cold forming starts with almost the exact amount of material needed. Another huge advantage is that cold forming is performed at ambient temperatures so there is no risk of oxidisation.


HIGH PRESSURE Cold forming works by forcing copper into a die at high pressure. Because of its relative simplicity, the process was traditionally used to make low-cost components such as rivets and fasteners. However, it can also make precision parts – at high volume, and reduced cost. Other benefits can include faster lead times, a better surface finish and superior mechanical characteristics. A prime example of how cold forming has been


used in the EV industry can be seen in power connectors. These components are critical to connect batteries to drive motors and for


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charging electric vehicles. Power connectors are used in charging units and in the motors that drive each wheel. Manufacturers work hard to improve connector efficiency, in order to minimise power losses while reducing weight and cost. Cold forming has helped them achieve this. On a more technical level, cold forming


raises quality by plasticising metals along – rather than across – their grain boundaries. This produces parts with low levels of stress deformation and high mechanical integrity, which raises performance and reliability.


PRECISION COMPONENTS Connectors are precision components, and cold forming can produce volume components with tight tolerances. At the same time, it can offer fine surface finishes, which typically require no further machining or polishing before plating. Furthermore, parts undergo work hardening during the cold forming process, which further improves their machinability and durability. This reforms the metal’s structure in a way that prevents further dislocations, leading to a stronger component. The increased strength is comparable to


that achieved by heat treating. However, there is a key difference: cold-working a cheaper material is more cost-effective than hot- working a more expensive metal – especially when a precision finish is needed. It is sensible to assume that copper prices


will keep rising, in parallel with increased demand from the EV sector. Certainly, as we’ve seen at Dawson Shanahan, using cold forming to process lower-cost copper into connectors could help manufacturers overcome a key emerging challenge in the EV sector.


Dawson Shanahan https://dawson-shanahan.co.uk


DESIGN SOLUTIONS | JUNE 2021 15


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