Design with Extrusions
Cross car beams are subject to twisting loads from road loads, so it is advantageous to use hollow structures that naturally provide torsional stiffness. Aluminum extrusions have a clear advantage in weight-sensitive designs because it is a low-density, easy to fabricate, and readily available material.
The Cadillac CTS program optimized a magnesium design with extrusions and cut 36% of the weight. The 6000 series alloys are common, namely the easy-to-extrude 6063, and stronger 6061 and 6005A when required in localized areas.
The designs shown here are difficult in die casting because the X and Y dimensions of the mold get extremely thick, resulting in a heavier mold. In turn, the mold is more expensive and requires more thermal mass to manage through the process. In addition, the length (Z) further drives the need for a long, heavy mold.
The typical cross-car beam program requires many molds, so the costs add up and the lead times grow. A die-cast beam tooling may cost $6 million whereas the extrusion tooling on the Acura was under $140,000. It is incredibly cost-effective to implement this geometry with extrusions, within compressed timelines.