With so many of our everyday consumer goods — from TVs to telephones, PCs to filing cabinets — made of either plastics or metal it must be borne in mind that these basic materials are, in fact, not so basic.
There are also highly complex decisions about whether such items have certain components made from metals, while others are in plastic. Therefore a discussion of these materials and some of their applications, to highlight key differences, is necessary from a number of perspectives.
Once, an engineering student would ‘time serve’, spending up to five years as an apprentice, learning and understanding how products were manufactured before turning his or her hand to the complexities of design and material choice.
Today’s further education system sets great store by the power of CAD, and the ability to solid model, constructing components and assemblies on screen, and in some cases even ‘testing’ the capability of the construction.
Usually these immensely powerful tools can draw upon the vast databases of materials provided by world-class manufacturers, who are continually developing and marketing new and ever more sophisticated polymers.
This means today’s designers, while undoubtedly being able to expound the differences between a myriad commodity, engineering and performance thermoplastics, will probably have only a superficial knowledge of metals. And they will be unaware that there are, for example, hundreds of stainless steels from which to choose.
Is it any wonder, therefore, that so many of today’s products are made of plastics?
The film The Full Monty helped show in graphic detail the decline of steel manufacturing in its Sheffield heartland. And while there has been a modest recovery, the metals industry overall is perceived as reactive and encumbered by the dyed-in-the-wool, producer-orientated attitudes of yesteryear.
Meanwhile, the more forward-looking plastics industry is seen as proactive and ready to listen and help, with polymer materials suppliers enjoying the reputation for far better new-project advice.
And while it is possible to buy almost any metal you want, you need to know your exact requirements and be prepared to wait a few weeks and pay for an excessive quantity.
This is quite different to the plastics industry, which is regularly coming up with new materials, offering try-out quantities ex-stock for prototyping and addressing fresh applications.
Yet there is definitely a place for metals in the modern world — if only we took the time to investigate and realise one very important fact. As a society we value metal.
Product designers are more aware in some areas than others of the benefits of the intrinsic value, solidity and aesthetics of metals. No matter how technically advanced a plastic watch may be, it’s still plastic. Other watches are advertised on the basis that they are made from titanium. There is no great design or technical benefit in manufacturing a watch from such an exotic substance more commonly found in aerospace engineering, but it is the image of the material that makes it desirable.
At a technical level, most plastics are inferior to metal components, suffering from shrinkage, joint line and RFI/EMI (radio frequency interference/electromagnetic interference) shielding problems. They are also less dimensionally stable and become degraded and discoloured over time by heat, light and ultraviolet rays. Plastics are hydroscopic (absorb water) and are gradually getting more expensive because of their oil content. metalwork, on the other hand, is recyclable in more than 95 per cent of cases, the exceptions being plated metals and bimetals which are non-recyclable.
But an even stronger argument in favour of metals is that plastic mouldings have a lower perceived value than metals owing to less weight and an inferior look and feel.
An MP3 player in its flimsy, economy plastic case is regarded as rather more disposable than a DVD player which has a sturdy metal cover. Indeed, for marketing purposes, many hand-held devices, although in plastic cases, are required to be coated to simulate metal and would be enclosed better by an actual metal pressing to absorb EMI and physical shocks.
This process, when applied to mobile phone housings, is very expensive and has environmental drawbacks. That is why Nokia, Samsung and other mobile makers are promoting their models as premium, top-of-the-range products on the strength of their stainless steel cases.
There are many other examples. Design icons of the 21st century in metal include the Eon Ice Classic titanium credit card torch and the Maglite torch. Better quality pens and spectacle frames all come in metal. An iconic Zippo lighter has always been stainless steel and is preferable to throwaway plastic ones. And even when plastics are used for appearance sake, such as on a Sky HD box, they are concealing a metal substrate that houses and protects the sensitive electronics.
So while we value metal over plastics, there are times when the metals manufacturing and supply industry falls short in terms of information, promotion and service in the face of the intense and innovatory competition from plastics.
Metals are crying out for a 21st century approach to meet the challenges of today’s products.
Tim Jones is business development manager of Clamason Industries
We may value metal, but the industry must get its act together if it is to compete with plastics in terms of promotion, innovation and new-project advice, says Tim Jones