Designing in Plastics

Over-engineered parts are target for metal replacement

Delegates at Eureka’s ‘Designing in Plastics’ Design Day learnt that many metal parts are still over-engineered – giving an opportunity to re-design the parts using plastics.

However, designers were warned that the rules of plastics design were quite different to those for metals.

“Recognise that plastic is not metal,” said plastics consultant John Hockey, who presented the keynote paper. “Use published data appropriately.”

Craig Norrey of polymer supplier DuPont, also urged delegates to recognise the limitations of plastics.

“Plastics and metals are different, and we must recognise this,” he said.

While plastics have “generally inferior mechanical properties” to metals, are more expensive per unit weight and are sensitive to temperature and moisture, he said their greater design flexibility and low density could lead to cheaper, lighter components with increased functionality.

Peter Frank, of new product design consultancy Product Innovation, warned that plastics had to be used intelligently within a design.

“A plastics housing should be an integral part of the design and not an afterthought,” he said.

He pointed to an example of a product he had worked on, in which the housing was designed intelligently around the internal PCB.

After lunch, three hands-on workshops put delegates through their paces.

Hi-Tech Group, which runs its own training days, trialled a new ‘hands-on’ workshop at the event. It asked delegates to determine which materials and moulding techniques were most appropriate to produce a set of components for an underwater camera housing.

DuPont’s workshop focused on a metal replacement case study. It detailed the steps behind how an aluminium support stand for a TV monitor was redesigned in nylon – saving 22% in both part weight and cost. A second case study showed how plastics replaced aluminium for an air intake manifold.

Distrupol challenged delegates to select an appropriate material for a furnace header, which had a working temperature of 220ºC. By entering design criteria (such as chemical- and temperature-resistance) into the company’s web-based materials selection software, delegates were able to narrow their search.

Eureka’s ‘Designing in Plastics’ Design Day was held at the Kaetsu Centre in Cambridge on 30 April, and attracted more than 70 delegates.

If you are interested in attending a future Design Day on plastics, please click here.