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33 "I started out my career at General Motors doing powertrain advanced manufacturing technology development. At that time we were looking at silicon- carbide reinforced aluminum for our connecting rods and crankshafts," Hall says. "The frst 12 years of my career was powertrain development. The last 18 were on body materials," she says. In the mid-90s, when she transitioned from powertrain to body, she worked on a program for developing a tailgate that had an aluminum outer and a polymer composite inner. "It's easy to stamp an aluminum outer but it is difcult to stamp the inner because it is a deeper draw and tighter radii and things." "Later I went on to manage a group that did advanced stamping materials and we focused on both aluminum and steel." All of which is to say that Hall has more than passing familiarity with alumi- num, the material that is providing the greatest competition for the material of which her current organization is a proponent. One of the things that Hall learned early on in the auto industry was that costs are a huge consideration. "You have to be very careful in your selection of materials. You have to look at the cost of materials. Cost of manufacturing, including any infrastructure changes you have to make." As in: "When we introduced aluminum into our stamping plants at General Motors, it required multi-million scrap- sorting systems for each plant." That's just for segregating the materials. Hall also points out that there can be signifcant changes in the body shop necessitated by making a move from steel to aluminum, as in using mechanical fasteners in place of spot welds, which can mean a whole new automation setup. But there are some details that can't be overlooked. Details that may measure just tenths of a millimeter. Hall explains that when stamping aluminum, trimming can present problems, particularly if there is die wear, and she points out that wear is a common problem with aluminum stamping due to the abrasiveness of the material. "Aluminum tends to create slivers if you don't trim it properly, so the clearance between the working tools is critical." The issue with these small slivers, she says, is that because the sheets tend to be covered with lubricant, they get carried along to the next station. "If it is an exposed outer panel, you'll get little imprints of the slivers." Which is not good for a Class A surface. Steel? "It doesn't sliver." If the clearances aren't right, there can be a jagged trim. While this generally isn't a problem, she acknowledges, "If you get a ragged trim and stretch it later on in a fanging operation, you could get a split." Mild steels are one thing. But they are giving way to higher-strength steels. These steels, like aluminum, have less formability. So might a company not decide that if they have to start dealing with diferent material requirements when it comes to handling and processing them, they might as well make a switch This is what is sometimes referred to as a "banana chart," given the general shape of arc that starts on the left side at "Conventional Steels" and goes down toward the right. As Jody Hall of the Steel Market Development Institute explains, the materials along the bottom in orange are high in strength, but difcult to form. These are the frst-generation advanced high-strength steels. Consequently, work is being done to improve the formability while not giving up on strength, which is the grey bubble, "3rd Gen AHSS." The second generation? They're the austenitic stainless (annealed) and TWIP.