CASTING INNOVATIONS Torpedo Body Cast With Vertical Pouring Process
AlumAlloy produced the cylindrical bodies by vertically filling the mold. When the U.S. Navy needed to
produce recoverable exercise torpedoes, known as REXTORPS, it initially explored manufacturing the 4-ft. fore- body section as an aluminum casting. Te X-ray inspection requirement and the design’s varying wall thickness ini- tially led to significant complications. Te ends of the cylindrical torpedo body are about 2 in. thick and the walls go from a thickness 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
The final castings measure 4 ft. in length with a varying wall thickness.
two years of effort, the U.S. Navy be- gan exploring other options, including boring the section out of solid stock. But David Howell, owner of Alum-
Alloy Company Inc., Ontario, Calif., was pretty sure he could meet the requirements of the casting. In fact, in 2006, he was so confident that he offered the part buyer a deal that was difficult to refuse. “If we do not give you a first article
by the due date according to your satisfaction and all the X-ray require- ments, you don’t owe us a dime,” Howell said.
Te first two metalcasters had at- tempted to produce the torpedo bodies by positioning the sand mold on the floor so it would fill horizontally. Te 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 symmetry of the casting and can keep bubbles from forming in the mold cavity,” he said. “It’s what we call modulated vertical 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 significant savings compared to the cost to machine the cylinders from solid billet. Since delivering those first accept- able samples, AlumAlloy has contin- ued to produce more than 100 parts per year. Te company regularly uses its modulated vertical pouring process for a large majority of its nobake cast- ings, including motor housings as large as 1,000 lbs. (454kg). “Te applications for castings are
The torpedoes are used for practice and are meant to be recoverable and reusable.
endless,” Howell said. “Te challenge is for engineers and buyers to see the possibilities—and we have a passion for meeting those challenges.”
August 2014 MODERN CASTING | 57
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