Two of the factors that aremost critical in automotive part design are cost and time-to-market, and they are particularly important when they involve multistep processes. Injection machine maker Engel and several of its partners have developed “Dolphin”, a two-component moulding technology that makes soft-touch parts on one press in less time than with conventional techniques, and at less cost. At the SPE Automotive Innovation Awards 2012, the first commercialised Dolphin interior trim components, fitted in the Mercedes Actros, made it to the finals of the Body Interior category.
Soft-touch interior in the Mercedes Actros truck (photo: Daimler)
The Dolphin process competes in the automotive interiors area with traditional soft-touch fabrication methods. They use solid substrates, polyurethane foam, and slush-moulded vinyl skins, each fabricated in a separate process prior to assembly, and not recyclable. The traditional production method requires separate production of the various and subsequent assembly by means of polyurethane foam, to weld the two elements.
Dolphin’s production cycle takes place within a single injection-moulding machine and in a single step. The first commercial application of Dolphin technology is in the four panels that make up the dashboard installed in the cabin of the Mercedes-Benz Actros truck, manufactured by Daimler.
The Mercedes-Benz Actros truck features the first commercial Dolphin technology application (photo: Daimler)
Here’s how it works
The Actros dashboard also includes the lower part and its fold-away drawers. It has a total width of over 2m, and is available in two colour versions with different colour matchings between light beige, black and grey.
The development process included several years of collaboration between Engel Austria, Swiss mouldmaker Georg Kaufmann, resin producer So.f.ter. (formerly the P.Group of Ferrara, Italy) and US-based Trexel, which supplied the MuCell microcellular foam process that is integral to the Dolphin process.
Dolphin uses a Kaufmann-designed mould, which mounts on a rotating table in an Engel Duo Combi M two-platen press with two injection units. The dashboard’s rigid support structure is moulded using Reblend, PC / ABS alloy from So.f.ter. The mould first rotates horizontally and, in the second step, Pibiflex thermoplastic elastomer from So.f.ter is moulded onto the substrate, using the MuCell process, and bonds the two materials while forming the soft-touch layer on the structural substrate. During the foam-moulding step, another substrate is fabricated on the opposite side.
The incorporation of Trexel’s MuCell process (which creates a microcellular material structure through the introduction of precisely metered quantities of atmospheric gases) into the moulding for the soft-touch layer eliminates the need for separate production of the various parts and their subsequent assembly and welding by polyurethane foam. An additional advantage is that parts foamed with the MuCell process can be recycled within their original polymer groups – unlike chemically foamed plastic items.
Cross section of the combined materials used in this application of the Dolphin process (photo: Trexel)
With Dolphin, the finished part is a multilayer construction of substrate, microcellular foam core, and soft-touch skin. Textured inserts can be used to give the surface a look of grained leather.
Recycling, in-plant and at the end of vehicle life, is facilitated by the use of a (mostly) polyester resin structure and the elimination of thermoset polyurethane foam, a common component of slush-moulded parts. There is no scrap in the Dolphin process, and sprues can be recycled in the product (carrier) as impact modifier.
Beyond the technology, Dolphin offers economic advantages that distinguish it from competitive processes. These include reduced capital investments in moulds and machinery, as only one moulding cell is required for fabrication. The project’s partners estimate 30% to 40% cost savings on total system cost are achievable; there is no separation between direct and indirect costs due to the very different methods of production. The Dolphin process can be translated to all OEMs.
Single-cell manufacturing provides simplified process control, fewer workers, reduced floor-space requirements, no secondary processes like trimming and assembly, and more efficient supply and handling of raw materials.
www.trexel.com
