innovations CASTING
Torpedo Body Cast With Vertical Pouring Process
TORPS, it initially explored manufac- turing the 4-ft. forebody section as an aluminum casting. T e X-ray inspection requirement and the varying wall thick- ness required by the design initially led to signifi cant complications. T e ends of the cylindrical torpedo body are about 2 in. thick and the walls go from a thick- ness of 0.25 in. near the edges to about 2 in. near the center portion. After two metalcasting facilities failed to produce quality castings after two years of eff ort, the U.S. Navy be- gan exploring other options, including boring the section out of solid stock. But David Howell, owner of Alum-
W
Alloy Co., Ontario, Calif., was pretty sure he could meet the requirements of the casting. In fact, in 2006, he was so confi dent that he off ered the part buyer a deal that was diffi cult to refuse. “If we do not give you a fi rst article
by the due date according to your satis- faction and all the X-ray requirements, you don ’t owe us a dime,” Howell said. T e fi rst two metalcasters had at- tempted to produce the torpedo bodies by positioning the sand mold on the fl oor so it would fi ll horizontally. T e lower half of the casting would pass X-ray inspection, but the top half wouldn’t. Howell’s solution was to reposition the mold so it was standing up and use a vertical pouring method proprietary to AlumAlloy. “Our system takes advantage of the
hen the U.S. Navy needed to produce recoverable ex- ercise torpedoes, known as REX-
symmetry of the casting and can keep bubbles from forming in the mold cavity,” he said. “It’s what we call modulated ver- tical pouring, because we can control the speed of the metal during pouring.” With a single large core in the 6-ft.
tall nobake mold, the castings require minimal machining. Additionally, the 210-lb. practice torpedoes, cast in aluminum alloy A356-T6, represent a signifi cant savings compared to the cost to machine the cylinders from solid billet.
Since delivering those fi rst accept- able samples, AlumAlloy has continued to produce more than 100 parts per year. T e company regularly uses its modulated vertical pouring process for a large major- ity of its nobake castings, including motor housings as large as 1,000 lbs. (454kg). “T e applications for castings are
endless,” Howell said. “T e challenge is for engineers and buyers to see the possibilities—and we have a passion for meeting those challenges.”
AlumAlloy produced the 4-ft. cylindrical bodies by vertically fi lling the mold.
The casting’s inner wall proved a challenge.
The torpedoes are used for practice and are meant to be recoverable and reusable. May/Jun 2014 | METAL CASTING DESIGN & PURCHASING | 49
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