Plastics has new competition in the auto industry.
With General Motors Corp.'s introduction of a proprietary aluminum-forming system it calls ``quick plastic forming,'' the carmaker is signaling that it plans to use the lightweight alloy for more auto body applications, especially in the low-volume vehicle category that is composites' specialty.
``This allows us to go after very eye-catching designs in low-volume vehicles, and that's one play we'll be making,'' Alan Taub, executive director of GM's Research and Development Science Labs, said during a Jan. 27 press conference at the Warren facility.
The system's ``sweet spot'' will be in vehicles selling less than 100,000 units annually. Composites generally are most cost-competitive on specialty vehicles selling up to about 70,000 units each year.
Quick plastic forming refines the ``superplastic'' aluminum system - used for years in the aerospace industry - making it affordable for the auto industry. The technology borrows basic concepts from plastics composites molding - which gives it its name - in that workers pre-heat an aluminum sheet, then use compression to mold it into complex shapes.
GM can produce a part in one automated step, with one one-sided mold. Traditional stamping processes require multiple dies for steel, and stamped aluminum cannot be turned out in the deep draws and shapes designers desire, Taub said.
Aluminum costs more and is less flexible than steel, he noted. ``What we've done is to tweak the processing of the material to get it into the state where it's actually more formable than steel.''
And with lower tooling costs, aluminum actually can compete with lower-cost steel on low-volume vehicles, he said.
Any time the production level goes past 100,000 vehicles, it makes more economic sense to stick with the cheaper steel, with the higher tooling costs spread across more cars and trucks.
General Motors has two QPF forming cells in use at its New Hudson, Mich., plant. It has no intention at this point to market the process outside its own operations, Taub said.
Detroit-based GM already has put the process to use on one vehicle, in the lift gate for the Malibu Maxx. Without it, the gate probably would have had a steel structure with a sheet molding compound exterior skin.
The one-piece aluminum gate weighs in at 20 pounds, compared with 39 for a steel-and-SMC, two-piece unit.
But the composites industry is not seeing the aluminum process as a full-on assault. If anything, GM's development signals that the world's biggest automaker is open to new material alternatives.
``It's a clear indication of a changing paradigm at GM,'' said David White, chairman of the Automotive Composites Alliance. ``They're getting out of the standard steel-stamping frame of mind.''
Traditionally, composites have had a difficult time getting onto GM vehicles, with the notable exception of halo vehicles such as the Chevrolet Corvette and the new Cadillac XLR.
With the carmaker opening its design and production doors for aluminum as an alternative material, composites also may find eased entry, said White, who also is a vice president with Dearborn, Mich.-based Meridian Automotive Systems. Resins still are cheaper than aluminum, and offer more alternatives for low-production vehicle runs.
``The lightweight [material] pie is growing, and composites will be growing with that pie,'' he said.
And GM has not given up on polymers. QPF is just one more consideration, Taub said.
``SMC, as well as [resin-transfer molding], is always going to be an option,'' he said. ``It depends on what you want. Aluminum will give you lighter weight, but at a higher material cost. We're fortunate to have the technical know-how to pick the right material and the right process for each application.''
The company already has rejected a demonstration all-aluminum-body vehicle made with QPF, deciding that was not the right application for the material or the process.
``What we can do now is to have a process within the company that looks at the entire menu of body materials, of the body build, of our suppliers, and looks at all the different materials and processes,'' Taub said.