Traditionally the realm of metals and alloys, the under-bonnet of the modern car is increasingly being manufactured in plastics. Perhaps not surprising considering the weight savings, low manufacturing cost and increased design freedom the material offers, even in what is traditionally a high-temperature environment. A new resin developed by Albis Plastics not only allows this freedom of design for internal and external automotive components, such as speedometer housings, dashboard fascias, air intake manifolds and connectors, but also allows decoration and branding of engine covers, enhancing the saleability of the car.
Materials Used in the Engine Beautification Process
The metallic engine beautification assembly is manufactured using Albis’ colour compounding technology. The multi-shot moulding technique uses a formulation of proprietary flakes and additives developed through years of research and development. The main metallic element is a high heat-resistant (thermal stability of around 130°C) glass fibre reinforced nylon 6 mineral mix, which meets all the under-bonnet requirements of a modern motor vehicle.
Properties of the Reinforced Polymer Used in Engine Beautification
‘This material provides the strength stability, and the chemical and thermal properties required by the automotive industry - the mineral also gives low warpage,’ says Andy Pilling, Technical Service and Application Development Engineer at Albis. ‘It’s a very easy flow material so you can achieve thin wall sections - any size or shape, the material will actually fill it.’ The technology is not limited to nylon. Any polymer-based resin can be used to achieve a variety of metallic effects.
Engine Covers that Don’t Need to be Painted
Usually, engine covers are painted or sprayed, which not only involves the logistical costs of getting it to a sprayer, but the high percentage of covers that have to be rejected because of scratches incurred during transportation. The Albis plastics assembly requires no finishing, i.e. painting, and the process eliminates the problem of scratching because the metallics are compounded into the resin. ‘If you scratch the surface all you get underneath is more of the metallic effect, so you don’t actually see the scratches as such - they sort of disguise themselves,’ says Pilling.
Another advantage is the elimination of knit-line defects that are often a problem when using more commonplace masterbatch additives or traditional compounding materials. ‘If you mould in a hole or a cut-out section, when the two flow paths come together you get a very dark grey/charcoal coloured knit-line,’ says Pilling. ‘Ours is the first patented technology where you get a weld-line and flowline-free formulation.’ Figure 1 shows a BMW Series 3 engine cover manufactured in glass/mineral-reinforced nylon 6 using a flow-line-free compound with a brushed silver effect that resembles aluminium.
Figure 1. BMW Series 3 engine covers manufactured from reinforced nylon 6, with a brushed silver effect resembling aluminium.
Processing Advantages of Flowline-Free Formulations
Weld/flow-line-free metallic formulations give tremendous latitude in gate locations and polymer flow patterns, reducing time spent on re-design or design modifications. Changes to the engine design itself are no longer a concern to the end visual characteristics. ‘If an engine changes, the cover changes with it,’ says Pilling. ‘The advantage we have is that it doesn’t really matter how that design changes. We can still gate and feed the resin from anywhere because there isn’t the problem of weld-lines developing.’ Previously, in response to design change, manufacturers using traditional forms of metallic masterbatch would have to change the way the resin was fed to disguise the weld-lines.
Black is no longer the only option for under-hood components. As well as a range of different shades of grey and metallic silver, Albis are now experimenting with a variety of other colours. As yet the colours haven’t come into application, but we have trialed them,’ says Pilling. ‘We have tried a green for certain power tool manufacturers, reds, which we hope will go onto GTI models, as well as blues, yellows and aquamarines.’
Designing with the Reinforced Polymeric Material
The new resin has been very much geared towards freedom of design, with Albis capable of supplying the material to manufacturers to meet their design requirements. The Technical Services and Application Development (TSAD) team works closely with the OEMs (original equipment manufacturers) to provide design and tooling advice prior to production. With the aid of rheological mould design (Moldflow) concentrating on fill patterns, pressures, gate locations, warpage, sinks and cooling, and strength and rigidity calculations made using finite elements analysis, Albis looks to provide a ‘right first time’ philosophy. ‘Our material is more expensive to begin with and we don’t hide that fact,’ says Pilling. ‘The advantage is that once it’s moulded it is finished, so there are no extra costs.’
Following the success of the BMW project, Albis is targeting the main automotive OEMs.
Advantages of Plastics over Metals
Compounded metallic effects are, ‘value added design’ materials that negate the need for expensive, time consuming post processes. ‘Plastics are traditionally cheaper than metal forming,’ says Pilling. ‘There are also things you can do with plastics that you can’t do with metals, for example adding a polyurethane foam insulation, which provides sound deadening properties.’
Although it is unlikely to please the metals community, it is hard to ignore the fact that plastics are making dramatic inroads in under-bonnet and interior automotive applications - bringing strength and beauty to the modern car.