SURFACES | AUTOMOTIVE
sector – from innovative air ventilation systems to highly integrated cladding and covers to function- ally demanding instrument panel modules and centre consoles. Requirements for the part are many, EMS-Grivo-
ry said. The lamellae are up to 335 mm long and as this is a visible part, excellent surface quality is necessary along the whole flow length. Swirls near the gating system caused by wrongly oriented glass fibres (this material has 60% glass fibre reinforcement) must be avoided and a precise ventilation system in the mould is needed to prevent surface porosity. Exact dimensional adjustment between the lamellae, housing and support is also essential. “Grivory GVX-6H easily satisfies all these requirements,” says the supplier.
Silver throughout It’s not always necessary to use high-end thermo- plastics to get high-end surface quality. A. Schul- man offers what it says is a unique silver metallic product line, which is based on various blends and polymer-based materials – including polypropyl- ene. Grades are formulated for improved process- ability. They can also be supplied with different surface effects and different polymer bases. Silver metallic effects are often hard to achieve, as weld lines or flow lines need to be avoided, the com- pany notes. “This is why the company makes sure that its customers and experts collaborate closely in order to achieve the surface effect needed.” Horst Klink, Sales Director for the EMEA region,
said A. Schulman has succeeded in developing compounds that produce a silver effect on part surfaces without tiger stripes. The effect can be used in auto parts such as skid plates, located below the rear bumper, and which are normally painted to obtain the silver effect, but which quite easily show up damage from stones kicked up from the road surface. Painting introduces an extra expense, and increases reject levels. “We don’t refer to it as a colour, it is an effect, because it involves a complete additive package,” Klink said. Last year, A. Schulman received the “Grand”
award for the silver-effect skid plate of the Mer- cedes-Benz GLA from the European arm of the
Below: Audi Q7 air vent with lamellae made of EMS Grivory GVX-6H
Society of Plastics Engineers (SPE) in the organisation’s Automotive Parts and Components competition. The Mercedes part is moulded in polypropylene, but Klink said the effect can now be achieved in various polymers and with various shades. The effect is now also being used in non-automotive applications, such as vacuum cleaners and even running shoe soles. Also in PP, but back on the inside, the instrument panel carrier of BMW’s 2017 Mini Countryman is this year’s winner in the Body Interior category of the Society of Plastics Engineers (SPE) Automotive Innovation Awards. Materials supplier Sabic said use of its Stamax long glass fibre-reinforced PP, coupled with core-back injection moulding technology to facilitate foaming helps reduce the part’s weight by about 15% versus a comparable solid plastic component. In the core-back process, material is injected to completely fill the mould; a core then retreats to allow for foaming with a physical blowing agent. This technique increases the wall thickness of the part from 1.9 mm to 4 mm and delivers the required strength and rigidity without adding weight. The Tier 1 supplier on this program is International Automotive Components (IAC) Group. The toolmaker is Siebenwurst. Sabic performed extensive CAE warpage analysis to predict warpage behaviour of the part. This evaluation, carried out early in the develop- ment process, provided valuable insights for the design of both the part and the mould, which enabled building the mould correctly the first time, Sabic said. “This sort of computer simulation is standard
practice when it comes to solid plastic parts, but the industry is still in the early stages of developing simulation tools for foamed plastic parts,” said Scott Fallon, Sabic’s global automotive business leader.
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Skid plates that are painted to achieve a metal effect (left) quickly show the effect of stones kicked up from the road. Parts that have the effect all the way through, using A. Schulman
material (right), do not
www.injectionworld.com November/December 2017 | INJECTION WORLD 51
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