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Daimler takes up Dolphin process in Actros truck

By David Vink
Posted 16 November 2012

Daimler's Mercedes-Benz business launched its New Actros truck in June 2011, which it said was "developed from scratch", with a new interior design including a soft-touch cockpit. The cockpit is injection moulded using the Dolphin process, which combines foamed-in-place technology with two-component hard/soft moulding. It is produced in a plant in Worth, Germany, located within Daimler premises but operated by Italian automotive moulding company Sole, which is part of the Prima injection moulding group and a Dolphin consortium licensee.

Cockpit parts are produced by Sole using Engel Coinmelt decompression technology on an Engel Duo 1700 Combi M two-platen injection moulding machine. This is equipped with a horizontal intermediate rotary table system, a multi-axis robot and physical foaming technology.

Dolphin was originally developed by Engel with Swiss mouldmaker Georg Kaufmann and materials suppliers BASF and P Group (now So.F.Ter) in 2007, based on the use of BASF's Ultradur PBT for the primary rigid component and thermoplastic elastomer (TPE) from P Group. But Sole's business development director Giuseppe Maiarellei told European Plastics News at the company's headquarters in Oderzo, Italy, where the cockpit was displayed in its showroom, that the material solution has now changed from the original concept.

In March, So.F.Ter announced its involvement in the New Actros truck application. It said it is supplying not only Pibiflex 3567 S (a TPE block copolymer from crystalline PBT and amorphous polyether glycol), but also the rigid component material, a mineral-filled PC/ABS blend called Reblend. So.F.Ter produces both materials in its Ferrara plant in Italy.

The Dolphin process was first evaluated in 2007 by automotive supplier IAC for part of a Scania truck dashboard, and the process was shown by Engel and its Dolphin partners at K2007 in cooperation with Johnson Controls Interiors. But the New Actros cockpit is believed to be the first Dolphin application in serial production.

So.F.Ter says the New Actros dashboard is made up of four panels extending across its entire 2m width, including a lower part with fold-away drawers. There are two colour schemes involving light beige, black and anthracite grey colour TPE soft-touch surfaces with "differentiated skin grain zones", the company says. As with the original concept, the soft TPE secondary component is foamed using Trexel's MuCell microcellular physical foaming process.

Dolphin consortium partners are talking of the potential to also physically foam the rigid component in order to save more weight than already achieved with the TPE surface. There should also be the possibility of using Pibiflex TPE for airbag cladding, where it is claimed to maintain breakthrough performance over a wide range of temperatures.

More details of the New Actros cockpit were provided at the end of March at the 2012 VDI plastics in automotive engineering conference in Mannheim, Germany. In a presentation by Mathias Dettinger and Thomas Batz of Damler's interior and system evaluation department in Stuttgart, Dettinger said the decision to go ahead with Dolphin was made in 2009.

Dettinger used visual examples to show how both trucks and cars have been shifting towards very similar interior designs. High quality appearance and feel of cockpits are now equally important in both sectors and are appreciated by truck drivers, who use their cabins round-the-clock as working, living and sleeping spaces. He commented: "Cockpit is cockpit", and there should be "no 'plastic' feeling, irrespective of hard or soft surfaces".

The preceding design of the Actros 2 truck in 2002 had already considerably narrowed the design gap with cars; the 2011 design even more so, and this helped the New Actros win the Truck of the Year 2012 award. Mercedes-Benz offers the New Actros with a cockpit in two different widths and three different equipment lines, with names such as "Style Line" and "Home Line", depending on the truck's purposes.

Dettinger compared the cockpit made with the Dolphin process with those made with conventional back-foamed foil and cladding with foamed foils. He pointed out that foil thermoforming and cladding processes can cause differences in surface appearance and require wider part tolerances, leading to uneven gap dimensions. Dettinger concluded that these other processes "are not forward-looking technologies".

He said that Dolphin, on the other hand, can achieve closer tolerances and should turn out to be a lower cost solution over the product life cycle (despite "very complex and expensive tooling"). Also surface graining textures are more reproducible, as they are determined and formed by the moulding tool.

A particularly positive feature of Dolphin, according to Dettinger, is that even if parts are designed with many reinforcement ribs in the rigid primary component, any consequent sink marks on the top surface are hidden by the foamed TPE. It also means integrated clips and snap fittings can be produced without sliders and designed in the same full thickness as the rest of the part, instead of being joined by a narrow section as would be needed with conventional injection moulded PP parts.

This aspect was well illustrated during the Engel Symposium open house in Austria in June, where the Dolphin process was demonstrated live. In this demonstration, highly ribbed parts clad in beige TPE were produced on a slightly smaller Engel Duo 1500 Combi M machine equipped with an Engel linear Viper 40 part handling robot.

Daimler's VDI paper contained a contribution by Engel technologies sales manager Michael Fischer, in which he stated that the amount of opening for decompression to form the foam in the mould affects the TPE foam's softness and density.

With compact Pibliflex TPE having density of 1.12g/cm3, opening the mould 2mm, for example, gives a 1:2 decompression ratio and foam density of 0.53g/cm3. On the other hand, a 4mm opening results in a 1:3 decompression ratio and density of 0.37g/cm3, with an associated softer feel.

The ability to make such adjustments is important, as Dettinger said in his part of the VDI paper "the areas in front of the driver and front-seat passenger should be soft, but the central shelf area should not be in soft touch". The same TPE is used for the soft and hard touch areas, with respectively Dolphin and non-Dolphin two-component moulding. This ensures "the same colour and gloss", while "tactile properties are alike, except for the soft touch", Dettinger said.

When the New Actros application was announced in December 2011, other series applications for Dolphin were said to be under discussion. At the Engel Symposium in June, a demonstration example was displayed of a Hyundai Mobis car dashboard made with the Dolphin process, showing its applicability in cars as well as trucks.

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