Advanced materials benefit fastener manufacturers

Written by: Justin Cunningham | Published:
Advanced materials benefit fastener manufacturers

There has been a trend in recent years of using unconventional materials on conventional parts and components. Whether it is to remove weight, offer superior performance, allow performance in extremes, manufacturers and suppliers are offering more product variants as a result of material developments.

This can be seen in the automotive sector which is increasingly using lightweight plastics to remove weight from structures. Equally, the aviation industry is using composites to do the same. But material developments are not lost on fastener companies, which are also riding the trend to offer product differentiation in a market where that can be hard to come by.

To cope with very hot applications, Goodfellow has developed a ceramic fastener that is capable of being used at 1650-1700°C. Ceramics offer many advantageous properties, particularly when it comes to managing heat. Not only do ceramic components block heat, they also have a low thermal expansion, are practically immune to corrosion, and most acids or fluids have no effect on them.

The fasteners are generally sold in low volumes to fairly specific sectors, which include space and research applications. But it is demand from these industries that drove Goodfellow to develop them. The fasteners are made in both alumina and high strength zirconia, and have the distinct advantage of not only being able to operate at extremely high temperatures, but are produced much more cost effectively than ceramic fasteners previously on the market.

James Taylor, sales supervisor of the ceramic and glass division at Goodfellow says: "The difference with the ones we are supplying is they are actually injection moulded. Previously they were manufactured using high pressure moulding. The injection moulding process reduces the cost as it is just a case of using a simple mould and repeating that."

The production of the ceramic fasteners is being driven by applications and is a response from customers needing fasteners that will cope with extremely high temperatures. However, ceramics have always been problematic as an engineering material because of brittleness, and these fasteners are no exception. Over-tightening a bolt will crack it, and probably break the head off completely.

"If they get a slight crack on them, if they drop or if too much pressure is put on them, they shatter," says Taylor. "There is no deformation. But, you wouldn't really use these for tightening, that is not there typical application."

The bolts have a four-point bend strength of 352MPa and a maximum service temperature of 2,200°C, and come in a variety of metric and imperial sizes. The company claims a standard M2 bolt is actually stronger than an equivalent Nylon bolt but with other inherent material advantages.

Using material developments to find a niche in low-volume specialised markets has been a success for Goodfellow. However, TR Fasteners has found success in using materials to exploit higher-volume applications. It has been a supplier of plastic fasteners for sometime but has recently been identifying applications that can use plastic fasteners in place of metal alternatives.

"We are moving in to an area with a tremendous market in the plastic side of things," says Kevin Rogers, plastics product sales manager at TR Fastenings. "TR has been a traditional metal based fastener company. Though selling a lot of plastic fastener parts, they have always been considered a category added on to the other business. But it is now a core product."

It has found successful application, and replacement fastener applications, on the Ariel Atom sports car using plastic fasteners to help take weight out of the structure. This makes for a good example of where a standard plastic fastener did the job adequately.

But it is not just for weight removal that TR has found applications. Plastic fasteners can lend themselves to assemblies. Though the actual part might be more expensive, by speeding up production, the overall cost to the customer is often reduced.

"We might see three metal fasteners in an assembly," says Rogers. "But, why use a nut, bolt and a washer, when you could use a two-piece plastic rivet that takes half a second to apply? That is where the innovation is."

TR has evolved from being a traditional fastener company that also sells plastic fasteners to making plastic fasteners a core range. However, to really exploit this evolution, it is increasingly approaching its clients and asking to see their processes to see if they can improve them.

"We are constantly being asked to cost down," says Rogers, "but we cannot take any more cost out of the parts. However, we can suggest using a plastic part if there might be some production benefit."

Plastic fasteners are not for every application of course, and like everything in engineering there are tradeoffs and limitations. There are structural limits to plastic fasteners where they might need to support certain loads, or tightened to specific torque ratings. Inevitably in these situations, a metal fastener will be used to give the necessary strength.

However, many applications do not require these specifics, with the electronics industry being a case in point. Where it traditionally uses small metal fasteners, TR is encouraging the uptake of plastic rivets. However, the buying power of larger electronic companies means the screws are already extremely cheap.

"We could have the instance where the plastic products are actually more expensive," says Rogers. "However, we might be able to reduce the assembly time by some 75% so that there could still be substantial savings to be made. We just need to change that mindset."

The metal fastener industry is very regimented, with many international standards in place. "With many plastic fasteners you do not have that," says Rogers. "So it is not as well regulated and there is an awful lot that requires you to use common sense when you are using them.

"Plastic fasteners are rarely used for heavy duty industrial applications. They tend to be more internal and for smaller diameters. A chassis bolt might be a big M16 size, but you are not really ever going to have something that big in plastic. Applications are suggested on a logical fit for purpose basis."

Another design advantage of plastic materials is the ability for their properties to be manipulated. From the possibilities of having various colours to being made flame retardant, it allows for many potential applications than many engineers might first think.

TR believes that plastic fasteners will open up more design opportunities – particularly in the automotive industry - and as a result has got PPAP level 1,2,3 to give customers confidence in the supply chain and ensure they produce a product that consistently meets set out requirements.

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