Making contact with metal bonds

Using bimetal and trimetal bonded composites can solve many problems and generate significant cost savings for engineering companies, says Samuel Taylor (STL), manufacturer of precious metal contacts. Ed Hill finds out more.
Samuel Taylor manufactures electromechanical parts that are exported around the world. Lately the Redditch, Worcestershire based company has made advances in bimetal and trimetal composites and is keen to highlight the potential these new materials have across many applications.

Managing director Alastair Gordon says many engineers are unaware of the cost of contact problems and when the issues are discovered often time and money has already been wasted. The head of the contacts material specialist, is urging manufacturers to think about the qualities they are likely to need in contact and other metal parts and to save time and money by speaking to suppliers such as STL at the start of the design process.

“Bimetals, which consist of silver and copper, are our legacy products,” Gordon begins. “They consist of a silver cladding onto a copper substrate. Recently we’ve introduced bonded trimetal composites which consist of silver alloys, copper and nickel 200. The nickel provides a very thin weldable backing and the copper provides an effective heat sink that allows for an absolute minimum of expensive silver alloys. This allows switches which traditionally use 0.3mm of silver alloy to run just as well but with only 0.1mm or even 0.05mm silver alloy – giving huge savings in cost.”

Precious combinations

Samuel Taylor can trace its history back to 1895. It was acquired by the present family in 1899 and is now in its fourth generation of owner-managers. Around 85% of the company’s output goes for export, mostly as components in the electrical arena. Its products can be found in anything from simple domestic switches to hybrid cars and electrical vehicles where it is making some of its latest advances.

Gordon continues: “In our case a key factor for our new products is the rising cost of precious metals. The whole emphasis is to minimise the amount of precious metals used in devices, whether they are switches or fuses. However the knowledge of how we join and combine metals can be used in all sorts of applications.”

Samuel Taylor believes UK firms still have to realise the full benefits of the latest trimetal bonded composites to replace solid welded or bimetal rivet constructions for their contacts. There is also scope for greater use of bimetal bonded composites using other materials and in other applications, such as the fuse industry.
Most high performance fuses use fine silver elements which are designed to blow at very specific fault conditions. The actual amount of silver required specifically for the element is in reality very limited so Samuel Taylor has taken the lead in the design and manufacture of an edge to edge bonded composite which concentrates the silver only where it is needed.

The aspiration of the company to utilise its knowledge and work with other firms has led to successes not only in the development of electrical parts for hybrid and electric vehicles but also adhesively bonded products designed and successfully tested, to destroy Improvised Explosive Devices (IEDs) on the battlefield.

“We find our customers have a need when they come to us and we help find a solution,” says Gordon. “For example we’re working on a water meter being developed for a foreign customer where they are currently using a solid silver part. We can halve the cost with a bit of ingenuity and create a part that will function just as well if not better. There is added value in engineering and design but overall it can be produced at a lower price.”

Electric moves

When it comes to hybrid and electric vehicles, the company is working on aluminium and copper composites used to link lithium ion batteries and producing more efficient heat sinks for electronic devices used in the control circuits.

“If you look at electric vehicles there is the potential for a whole new raft of materials and parts that are going to be needed,” Gordon comments. “They are being developed very rapidly and opportunities for new technologies in those vehicles need to be advanced. It’s about using technology in one sector of manufacturing and applying it to another. We make materials that can solve a lot of problems in the electric vehicle area.”
Another early stage working prototype has been the creation of a new bonded composite material including a ceramic-like substance which does not expand with heat but retains the conductivity of copper. The material is designed to withstand high temperature fluctuations without moving and cracking the joints between the busbar (electrical conductor) and high power thyristors.

“Electric vehicles are creating a whole new world,” adds Gordon. “It’s not just the cars themselves, but also the generating capacity. Things such as smart metering will also need to be developed.”

Going with a bang

In the defence sector Samuel Taylor’s understanding of materials has been applied to create a customised product that it claims makes better use of the Munroe Affect (which focuses the power of explosive energy) to safely destroy IEDs. The company combined the use of copper, a relatively dense but inert element with magnesium which burns at very high temperatures, to create a fast moving fireball capable of penetrating more than 500mm of sand and cement and exploding anything volatile in its path.

“The IED device shows how we can use two dissimilar materials in a novel way,” Gordon explains.
The use of two or three different materials combined into one single stamping is another of the company’s successes, saving a customer millions of pounds by using only the expensive material where it is actually needed. In this example of the company’s creative approach it produced composite parts made from steel and phosphor bronze assembled and stamped at more than 100 parts per minute using its own in-house design and build press tooling.

These projects demonstrate the understanding STL has of composite materials coupled with its innovative style of thinking and experience. Gordon maintains these qualities leave it well positioned to exploit other sectors of the engineering business.

“Our long-term approach may be unusual, but it is essential to success in this industry,” he concludes. “Our aim is to create and produce the best products possible for each application whilst always being cost competitive.”

www.samueltaylor.co.uk