Top honors in a recent competition sponsored by the Investment Casting Institute, Montvale, N.J., went to a radically redesigned air-inlet housing from Miller Castings Inc.
The inlet is more complex, but requires less machining and has greater corrosion and high temperature resistance. Wall thicknesses ranging from 0.07 to more than 0.7 in. added to the complexity of the part that's cast from a three-piece wax assembly. Miller Casting used a vacuum-cast nickel-base INCO 718 rather than casting from magnesium and aluminum. The near-net-shape casting is 8.76-in. tall with a 13.5-in. diameter.
Also honored was Howmet Dover Casting, Dover, N.J. The company won for its single-piece swirler for a gas-turbine engine. The 3.6-in.-long, 1.5-in.-diameter Hastalloy X casting overcomes critical durability issues inherent in the 27-piece assembly it replaces.
The swirler has a series of 0.070-in.-diameter holes on its inner cap, as well as 0.03-in. holes on the outer cap. All the holes are cast in, not machined. Investment casting is more repeatable, letting Howmet eliminate flow-rate tests on individual parts. Tight spacing between inner and outer cap surfaces makes traditional shelling techniques impossible. So Howmet developed a special dip technique to build shell layers in critical areas of the part. The part is machined after casting.
The final winner was a single-piece frame used on the 2004 Harley-Davidson Sportster motorcycle. The frame replaces a six-piece forging and stamped assembly. Investment casting improved part-to-part repeatability and reduced welding distortion. The 8.75 X 8 X 4-in. casting also costs 15% less and travels through manufacturing in only 75% of the time because it no longer needs to be welded. The casting from Signicast Corp., Hartford, Wis., serves as a mounting place for Harley-Davidson's proprietary isolation system as well as brake components, passenger pegs, wire harnesses, and various other components.
Other finalists in the competition were Hitchiner Manufacturing Co. Inc.'s Nonferrous Div., O'Fallon, Mo., Aristo Cast Inc., Almont, Mich., SeaCast Inc., Marysville, Wash., and Tech Cast Inc., Myerstown, Pa.