DuPont's Manifold Hits the Rub

Peer closely enough at almost any vehicle on the road and you'll most likely discover DuPont Automotive fingerprints somewhere. And in the case of Ford Motor Co.'s 5.4L SOHC Triton V-8 engine, they left a particularly significant one.

The 5.4L dons the first North American application of a multi-piece, vibration-welded nylon 6,6 lower intake manifold, developed by DuPont and tooling partner Montaplast of North America in conjunction with Ford.

Found in 1999 F-series pickups and the Expedition and Navigator sport/utility vehicles (SUVs), the manifold replaces an almost identical part originally designed for lost-core manufacture, but the component proved a good candidate for conversion to the new technique.

Ford has announced, incidentally, that it will boost production of the Triton V-8 by 50,000 units (to 811,000) this year at the Windsor, Ont., engine plant to meet demand.

Vibration welding really isn't new at all. In 1979, France's PSA Peugeot Citroen became the world's first automaker to apply the process to an intake manifold. Ever since, Europe has remained its biggest proponent.

Vibration-welded plastic manifolds have found a home in Europe for the last five years.

Plastic held a 45% share of the European manifold market in 1997, compared with only 25% in North America and 4% in Asia. GianLuigi Molteni, DuPont senior development specialist, says plastic's overall share of the global manifold market should double by 2000 or 2001- with a good portion going to vibration welding.

The process of vibration welding entails rubbing two thermoplastic parts together at such a frequency that the material actually melts and melds the parts together. Viable application of the process requires some specific conditions, most notably enough space available surrounding the part for the flange that results at the seam where the welding takes place. And the overall design of the manifold must be fairly simple. Ford's 5.4L engine presented both elements.

Though the process isn't an arduous one, it has advanced slower than lost core for obvious reasons. "Lost core developed first because it replicates casting," a far more familiar and mature manufacturing technique, says Kenneth W. Nelson, DuPont senior Technical Consultant. "And it definitely has certain packaging advantages." He says most V-6 engines, particularly those in a 60-degree configuration, provide such tight space limitations that vibration welding simply isn't an option. He cites the intake found on General Motors Corp.'s 3800 Series II V-6 engines, with its siamesed ports, as an example. Using lost core allows its relatively complex shape to be realized while still using the more lightweight and cost-saving nylon material.

Mr. Nelson says vibration welded nylon 6,6 parts will therefore most likely displace aluminum in manifold applications rather than those manufactured using lost core molding. The material itself confers a 30% cost and 50% weight savings over the more conventional material, with vibration welding contributing additional manufacturing savings.

And following the current industry-wide trend toward increasing integration of components, vibration welding enables DuPont to turn its attention to developing a total air/fuel system that can be supplied as a module. Mr. Nelson pictures this module to combine the valve covers, intake and fuel rails into a single nylon unit, thereby further reducing assembly time and complexity.