Technology

Cadillac's Secret Weapon: Plastic


Cadillac made an easy decision four years ago to take its Evoq roadster concept car from the auto-show circuit to the plant floor. After all, the high-end carmaker was launching its renaissance and needed a hot car to sell in low volumes, one that made a bold statement about the luxury brand's edgy new styling and heart-pounding performance. Caddy needed an exclusive and exciting car that could run with the stylish imports. The tough part for General Motors (GM) was how to get a $76,000 niche car to market without taking a bath on the development costs.

The answer? Cadillac's new XLR, the plastic luxury car. Nose to rear, Caddy's entry into this market is made almost completely of two kinds of plastic, save one small aluminum panel behind the convertible top. It's a similar construction to the body of the Chevrolet Corvette sports car, which also is now virtually all-plastic.

The initial investment in tooling for the XLR is much less than it would be for a steel body, says Dave Leone, the XLR's chief engineer. Plus, it's easier to make plastic panels with deeper bends and wilder shapes, so Cadillac was able to produce the car with the fancy styling of the original concept.

HARD BODY. If Cadillac sells all of the 5,000 or so XLRs that it plans to build in the next 12 months, the program will be profitable. It begins shipping this month, and Caddy dealers say enough buyers are putting down advance deposits that selling out the production run shouldn't be a problem.

While plastic is hardly new in cars, its use is growing. The XLR and its sister car, the next-generation Corvette, will be the only vehicles with all-plastic bodies in North America. But other auto makers are exploring more uses for plastic in panels and elsewhere to reduce weight and boost fuel economy.

One of the biggest challenges with the XLR was making its crisply styled body. The front end has such sharp lines, especially the way the front fenders wrap around the headlights, that using steel or aluminum would have been costly. If the front fenders were made of those materials, GM would have needed to stamp out several pieces and fit them together like a jigsaw puzzle.

MORE HORSES, FEWER POUNDS. Auto makers do that all the time, but the XLR would have required some more intricate pieces. That means higher costs, Leone says, not to mention more complicated assembly. Worse, building sections of a car's body with several pieces results in more creases and lines in the body. It just doesn't look as good. By using plastic, says Leone, "you can form complex shapes that you can't form out of aluminum or steel."

For a car like the XLR, weight is critical. GM built it on the next-generation Corvette platform. Execs wanted the XLR to stand up to pricey foreign two seaters like the SL 500 from Mercedes-Benz (DCX) and Lexus SC 430 from Toyota (TM), both made of metal. The XLR is faster than both. Not only is its engine more powerful than both rivals but the all-plastic body makes the Caddy 400 pounds lighter than the SL 500 and 200 pounds lighter than the Lexus.

In a 320-horsepower sports-luxury car like the XLR, fuel economy isn't much of a concern. But other auto makers are adding plastic compounds to lighten the load in their new vehicles. Many new Nissan (NSANY) SUVs have plastic rear lift gates, says Mitsuhiko Yamashita, president of Nissan Technical Center outside Detroit.

PAINT-SHOP MAGIC. So far, buyers don't seem to flinch when they discover that their luxury convertible or rugged SUV contains lots of plastic. Leone says Cadillac researched that issue thoroughly before going ahead with the XLR and found "the message from our customers is that they don't care what the material is as long as it has quality and durability." The XLR has plenty of interested consumers, and buyers don't seem to mind shelling out $40,000 for a Corvette, which once boasted a fiberglass body but has now evolved to use mostly plastic composites.

The one drawback is paint finish. GM went to great lengths to ensure that the XLR's plastic panels look like they belong on a luxury car. "You can't get plastic panels to have the same level of finish as metal panels," says Eric Noble, President of Car Lab, an automotive consulting firm in Santa Ana, Calif.

Plastic panels tend to dry with a texture that looks like an orange peel. So GM tore up the paint shop in Bowling Green, Ky., where the Vette and XLR are built, and created a new one that gives each panel some special attention. Metal cars are usually painted with the body panels on. But each XLR body panel is painted off the car on drying racks tilted at just the right angle. It takes twice as much plant space as any other paint shop and is more time consuming, but it still saves costs overall.

WORLD-CLASS RIVAL. Plastic has one big benefit for its owners: It's easy to fix. The two plastics that GM uses for the XLR are dent-free and corrosion-resistant. The softer plastics on the front end are unlikely to crack, says Leone. On the side panels and doors, the XLR shouldn't dent and will crack or break only in a serious accident. If they do, they're cheaper to fix. The local body shop will simply replace them instead of spending expensive labor hours refashioning steel or aluminum into shape and preparing it for repainting.

It may have taken some extra steps, but the XLR is shaping up to be a first-rate competitor with Mercedes and Lexus (see BW, 6/13/03, "Can-Do Caddy"). If GM can match its performance with future cars, then adding a little plastic in the body is a winning strategy. By David Welch in Detroit


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