At Interplas 2021, EPPM visited the Global Precision booth when a range of automotive components caught the eye. There Sales Manager Darren Webb discussed the materials and manufacturing processes involved.
A chrome-plated grill – a prototype built for marketing evaluation – was machined from an ABS material that can accept a chrome-plated finish. Intended to replicate what the part would look like in the production stage, the single-cavity prototype was produced using a pre-production tool and did not therefore possess the complexity and durability required as its injection moulded counterparts, although it does have the same end result: a part made with the chosen material that can be used for crash tests in pre-production. The grill has to have some mechanical properties in order to be able to support the weight of a lamp, but the only other real specification was for it to be able to have that high chrome finish, which you couldn’t possibly have on a polycarbonate composite part.
“A more functional automotive component would need to be more robust,” Webb said, “so a PC ABS or a nylon would have then been the preferred material. Likewise, for parts that require reduced friction, an acetal or oil-filled nylon offering better mechanical performance in that application would have been selected.”
Another eye-catching feature on the Global Precision booth was a leather-clad gearshift with a polyethylene insert, which offered softness to the touch, although the OEM’s materials selection, Webb added, would have also been driven by mechanical characteristics rather than aesthetics alone.
An automotive switch gear was displayed that contained ABS and translucent polyethylene to allow LED light to pass through the icons. “These materials would have been selected because of their thermal capabilities and insulation properties,” Webb confirmed. “That is something that would be recognised as an industry standard in terms of materials. A design company or OEM manufacturing something like this will engage at an early stage with the tool maker and with the materials supplier to determine what characteristics and specification will drive the material selection.”
The materials supplier will then work with them to ensure they arrive at the right solution. “It’s very much a collaborative effort that results in a better product,” Webb continued. “That’s why we always try to engage with our clients as early as possible and work with them through that process rather than arrive at a point further along, in case of any negative effects in the quality of the part or the manufacturing process.”
Driving range
What was most interesting was finding out whether plastics remain, and will continue to remain, as the ideal material for such automotive components. Webb confirmed that they are still the go-to materials for high-volume production in automotive applications, although he has seen very low-volume bespoke products manufactured for the high-end and sports car sectors that utilise 3D printing technology or composites and carbon fibres. “These will be determined by weight restrictions or by the manufacturing process,” he added. “In injection moulding, there is a high investment in front end for tooling in order to make the parts cost-effective for the manufacturer, which is required for high volumes. With low-volume niche markets that produce perhaps just 50 vehicles a year, they can often utilise more expensive manufacturing processes. So, you don’t have a tooling investment at the front end, which results in a part costing more but you can produce something bespoke to the application. You see that a lot with some of the new 3D printing technologies where they’re able to print a component that can’t be manufactured through injection moulding because of its complexity or functionality.”