Auto Door Panel Offers Looks, Feel, Economy

Design and production of automobile interior door panels have been the focal points of intense development work for some time. The result is a mix of production technologies that today includes laminating preformed hardboard, sandwich moulding, Hinterspritzen or backmoulding using textile inserts, multicomponent/colour moulding including foam, in-mould laminating, gas-assist, and more.

To those, add a choice of finishing techniques to impart the right look and feel. Various combinations of these technologies seem to multiply daily. Pianfei Engineering of Cuneo, Italy thinks that most and perhaps all of these solutions may have one unfortunate thing in common: high costs that go with overly complicated production.

Processing, Function, and Aesthetics

Pianfei, recently acquired by the well-known Tier One automotive supplier Lear Corp., has more than 30 years experience in auto design and production engineering. Its creations can be found in various models of the Fiat and BMW auto lines, among others, and 50 of its 900 people are engaged in design. Seeking to lower door panel costs with no compromise of the visual and tactile aesthetics that auto makers demand, Pianfei has come up with a unique, monolithic, single-material moulding that needs only a simple snap-in padded panel to be complete.

According to Pianfei's managing director, Attilio Gaggero, the overriding aim of this project was to prove the make-ability of this cost-saving design, and it has succeeded. Depending on the method used for comparison, overall cost savings can range between 20 and 30 percent, not to mention reduced production cycles and equipment purchase costs. To be sure it would work, Pianfei took this design project all the way to production, moulding panels in a normal steel mould on a standard 1,000-ton press. The finished moulding incorporates an integral pocket for passenger articles, speaker grill, arm rest, door lever housing, and snapfits for the decorative insert panel. The design of the nonappearance side also includes snapfits that simplify the automaker's assembly.

The Right Material

Finding a single material that satisfies the demands of structural integrity as well as offering good surface aesthetics and performance was Pianfei's objective, but not an easy task. Pianfei ultimately chose unfilled Daplen KC45 polypropylene from PCD Polymere. This high-crystallinity, new-generation copolymer, despite being a thermoplastic stiff enough to provide the required structural support, also provides the semi-soft-touch surface automakers want.

With the material's particularly low density, the finished moulding weighs only 1.8 kg (4.0 lb), or about .5 kg (1.1 lb) less than similar products, thus helping with weight reduction. Stiffness and lightness were each improved by using gas-assisted moulding, which Pianfei holds to be a relatively less complicated yet very cost-effective technology for this project. The part needs no postmould finishing.

Gaggero readily acknowledges that the cooperation and support Pianfei received throughout the development from PCD's technical center in Linz, Austria was invaluable, and included PCD doing Moldflow analysis that optimized both part and mould design. PCD was, he says, very sensitive to the variety of demands that this single material had to meet. This PP can be easily coloured to meet styling demands, and owing primarily to the absence of fillers, offers superior surface scratch resistance. Respecting the critical issue of passenger safety, Pianfei wanted a material with excellent resistance to splintering under impact, without the ductile behaviour that can result in sharp surfaces. Daplen KC 45 meets those criteria, and in the bargain provides very good sound insulation.

Besides the economy of using a standard mould in a normal single-component injection machine, as opposed to multicomponent moulding or in-mould laminating, the material itself contributes to the ease of processing. Its high elastic modulus makes part ejection easier, even in the presence of surface embossing and sharp angles in the design. Good flow and filling properties, plus almost invisible joining lines, yield an aesthetically pleasing panel that is not difficult or costly to produce.

The snap-in surface panel specified by Pianfei starts with a base of MPL sheet, and the surface fabric is ultrasonically welded on over acrylic padding. This yields an attractive curvature and rich-feeling softness, while still keeping production costs economic. Gaggero notes that the panel could easily be made in a variety of finishes to suit the auto designer's overall concept, a production flexibility that enhances the economic appeal and design freedom of this concept. The panels have been submitted to PCD Polymere for testing on behalf of several automakers, including VW and Opel.

Contact Information
PCD Italia
Mr. Bruno Sola
Via Ercolano, 8/10
20052 Monza, Italy
Tel: +39 (039) 20421
Fax: +39 (039) 2842735

Pianfei Engineering Srl
Mr. Attilio Gaggero
Via Cuneo, 27
12080 Cuneo, Italy
Tel: +39 (0174) 559511
Fax: +39 (0174) 585588