Casing the extrusion joint

Aluminum-alloy extrusions form everything from cabinets to car chassis. Here are some ways to join them. 500-hp Ford GT supercars ride on a chassis made almost entirely of welded-aluminum extrusions. Properly designed adhesive joints spread loads over a large area and are oriented to minimize certain stresses Hydro's Rotal hinges bring into mesh two extruded axially aligned gear sets. A third extrusion locks the sections together. The resulting joint is able to swing through 90 and requires no secondary machining. Aluminum extrusions connect four corner castings and one behind the passenger compartment in Ford GT supercars. Some 35 different extruded profiles from form a stiff, strong, and lightweight platform. Chassis are assembled using a combination of robotic MIG and friction stir welding. In addition, bolt-on extrusions add structural support to the engine compartment and also integrate into the bumper assembly. "In all cases, sections are tailored to the specific joining operation," says Hydro Welding Team member, Jim Brown. The ability to quickly modify extruded sections helped Ford go from initial design to production of three prototypes in just one year. The company plans to build about 1,500 of the supercars annually. The capacity to form complex shapes with relatively simple tooling — in a single operation — makes aluminum extrusions an attractive alternative to machined and stamped components. Throw in a variety of joining methods and the design possibilities grow geometrically. For instance, assemblies of smaller extrusions can replace single, larger units, without compromising structural integrity. Smaller sections are also easier to handle, can be made to tighter tolerances, and may lower die costs in many cases. But choose a joining method when spec'ing dies because sections are often made specifically for it. The elasticity of aluminum makes possible clipped joints, a method of snapping together multiple extrusions that cannot otherwise