DOE-funded Research Sparks Development of Manufacturing Technology Used in 2004 GM Production Vehicles
July 27, 2004
General Motors' manufactures the rear liftgate of one of the company's hottest new cars using a hot blow forming process that has its roots in manufacturing methods applied to superplastic forming of aluminum alloys. Superplasticity of Al-Mg alloys was investigated by DOE's Pacific Northwest National Laboratory (PNNL), General Motors (GM), and Kaiser Aluminum under a DOE-funded Cooperative Research and Development Agreement (CRADA) in the early 1990s.
The aluminum forming process that has evolved from "superplastic forming" into "quick plastic forming" permits production-volume manufacturing of complex-shaped body panels as one piece. In the past, such complex body panels were either restricted to use on low-volume specialty vehicles, or they were constructed with multiple parts and materials that added complexity and time to the manufacturing process, as well as weight to the finished vehicle.
When GM, PNNL, and Kaiser Aluminum first began working on superplastic behavior in 1992, the automotive industry relied on traditional die stamping for mass-produced aluminum body parts. That process could not create the kinds of complex body panel shapes manufacturers sought. The aerospace industry was using an aluminum forming process known as superplastic forming but it proved too slow and expensive for high volume production needed in the automotive industry.
The PNNL-GM-Kaiser CRADA identified compositions and processing techniques for several new aluminum alloys. Some of those alloys showed promise of being sufficiently formable at higher strain rates to allow cost-effective production of automotive components. Encouraged by the promising alloy development results, GM went on to develop its proprietary Quick Plastic Forming process around more conventional composition alloys (AA5083) that can be used for high-volume, lighter weight, more fuel-efficient vehicles.
The resulting process and material debut this year in the production of the 2004 Chevrolet Malibu Maxx rear liftgate. Prior to implementing the new forming technique and material, GM anticipated that the Malibu Maxx liftgate would weigh almost 40 pounds. The final weight is nearly half that thanks to the new material and process.