Cut cost, use plastic

Written by: Tom Shelley | Published:

A deeper knowledge of plastics materials can help designers to cut costs and add value to their designs. Lou Reade reports

Are plastics cheaper or more expensive than metals? Well, it depends on where you stand within the manufacturing process – and what type of material you are buying.
If you’re in purchasing, it’s more expensive. A kilogramme of an engineering plastic like nylon costs far more than its equivalent weight of steel – end of story.
But step to one side and the answer may be different. For a designer or manufacturer, these expensive materials can actually reduce costs – through greater design flexibility, lighter weight (which can cut fuel bills, for example) and ‘instant’ styling – removing the need for post-processing operations such as painting.
Delegates at next month’s Designing in Plastics Design Day – held at Buckingham House in Cambridge on 23 September – will learn some of the ways in which plastics can deliver these benefits. The materials are not a cure-all – some designs will always be made in metal – but in the right circumstances, and using intelligent design, they are the best materials for the job.
Steve May-Russell, of design consultancy Smallfry – who kicks off proceedings with the opening presentation – is adamant that design is king.
“You add value by giving customers what they want,” he says. “The perceived value of your product is very well communicated if the design is appropriate to the market. Good design is appropriate design.”
While he is not a plastics evangelist, May-Russell frequently uses the materials to enhance his designs. Among Smallfry’s successes are: a range of combs and brushes for Boots, whose sales grew 260% year on year following a re-design; and a shower head whose retail price doubled after a similar process. Both made extensive use of plastics.
In similar fashion, design consultancy Greaves Best Design found success with a new type of golf trolley – which kept cost down and standards up.
The GoKart powered golf trolley stands out from its competitors – being eye-catching, full of new features and durable despite sitting at the bottom end of the market in terms of price.
John Greaves, a partner at the firm, will explain how plastics are integral to the trolley’s design – and to its success.
“The materials selected facilitated innovation in the incorporation of springs, hinges, gears, and integral latches,” he says. “Tactile qualities could be introduced which enhanced comfort and allowed a firm grip.”
The trolley is compact and foldable – fitting into an envelope the size of this double-page – as well as being easy to handle, transport and store.
Plastics materials are used to create a durable, lightweight and low-maintainance product that is easily manoeuvrable.
“Overall, as the components were moulded, the number of parts could be reduced with cost savings resulting,” says Greaves.

XHEAD: Workshop highlights
DuPont – one of the event’s sponsors – will explain way in which to deliver performance and cost benefits using plastics.
Craig Norrey, technical programmes manager at the company, points out the designers have the greatest influence over the cost of a plastic part, whose “decisions predetermine the costs of production, mould-making and assembly”.
Choosing (and using) plastics wisely can significantly affect part cost, he says. Some of the important factors include: the ability to use low-cost assembly techniques such as snap-fits or welding; eliminating surface treatments – such as corrosion-resistance, thermal insulation or colouring; and designing parts with multiple integrated functions – so-called ‘part consolidation’.
The workshop will deal with a specific case study in depth: an automotive air duct in which seven separate components – made from various metals and plastics – were re-designed into a single plastic part.
The new duct was made from an elastomer called Hytrel, which exists in both rigid and flexible forms – allowing the various elements of the duct to be made using a single material.
As well as eliminating a number of post-processing and assembly operations – leading to a 20% cost reduction – the new part was less than half the weight of the original.
Another key element of the workshop will be a demonstration of DuPont’s radical Metafuse technology – and a sample of the technology will be on display. It will show a standard ping-pong ball – coated with a microns-thin layer of metal alloy – withstanding an 80kg weight.
In its workshop, rapid prototyping specialist Materialise will concentrate on the details of additive layer manufacturing (ALM) – and how it can help to slash lead time, cut manufacturing costs and create competitive advantage – through factors such as design freedom and weight saving.
A number of samples will show the capabilities of ALM technologies – including the One Shot, a folding, functional stool made of polyamide that was built in a single piece using selective laser sintering.
This technique enables the creation of the entire seating surface, legs and hidden integral articulations in a single shot. The stool emerges from the machine in its final form, with all axles, screws, springs and hinges concealed by the stool’s structure. MGX, the company behind the chair, has also produced a series of lamps using similar techniques – and these will be on show too.
The company will also demonstrate its Rapidfit system, which allows fast, efficient fixture design.
In the communal area, Materialise intends to demonstrate its Onsite online quoting system, which allows prototypes to be quoted and ordered at any time of the day or night.
There are two further workshops at the event: Distrupol’s will explain the importance of specifying an exact grade of material based on cost and performance – which is crucial to design success; and Holloid Plastics – from its perspective as a plastics moulder – shows how plastics can add value to engineered products.

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