Smart New
Roof module shows high-gloss appearance
The new roof module for the MCC Smart is the first large vehicle body part in which glass and plastic with similar stylistic characteristics have been combined to produce a high-quality painted appearance. The integrated roof module is manufactured by ArvinMeritor and comprises a high-gloss black laminated plastic panel housing a black-tinted sliding glass sunroof. The key to achieving a “Class A” surface finish on this non-painted part is a finishing system called “paintless film moulding” (PFM-System) by BASF.
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| Fig. 1: The roof module shows a high-quality painted appearance | Fig. 2: The PFM film is a coextrusion of ASA and ASA+PC capped with two layers of PMMA (photos: BASF) |
The roof module is made by thermoforming the PFM film
to the shape of the roof and injecting onto its inside surface a layer of
Elastogran’s Elastoflex, a long glass-fibre reinforced polyurethane foam.
Both the film extrusion and the subsequent thermoforming represented important
technical challenges for Senoplast and ArvinMeritor since either process can
affect the quality of the resulting surface. The injection pressure in the
foam lamination step is too low to be able to “iron out” any surface
unevenness. ArvinMeritor therefore worked closely with the manufacturer of
the high-performance thermoforming unit installed at its Gifhorn site. Post-moulding
assembly and finishing operations are minimized by integrating the main parts
of the sunroof’s sliding mechanism into the roof module during the foam
moulding process.
No painting anymore
The PFM film is a coextrusion of BASF’s Luran S (ASA and ASA+PC) capped
with two layers of PMMA from the Plexiglas models by Röhm. It meets all
requirements as regards chemical resistance, weathering, heat deformation,
scratch resistance and gloss. The PFM-System first became a commercial reality
in 1998 with the start of production of the Smart car’s all-plastic foam-laminated
roof, which at that time had a textured surface. PFM enabled a lightweight
roof to be produced while avoiding costly painting. The system is ideal for
modularized designs since it enables a perfect colour match and uniform surface
finish - irrespective of whether the individual parts come from different
suppliers.
www.basf.com
www.arvinmeritor.com
www.elastogran.de
www.senoplast.com
www.roehm.com
www.smart.com
A shiny cooperation
The integrated roof module is manufactured by ArvinMeritor, Gifhorn/Germany.
Aside from MCC Smart, the car maker, four other companies were involved in
the development of the roof module: Elastogran, Lemförde/ Germany, with
its Elastoflex polyurethane structural foam system; Senoplast Klepsch, Piesendorf/Austria,
which makes the high-gloss film Senotop; Röhm Formmassen (Degussa), Darmstadt/Germany,
the supplier of the PMMA-lidding laminate; and BASF Ludwigshafen/Germany,
which supplied the PFM-System as well as the film material.