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Casting Conversion Saves Optical Manufacturer $11,000/Yr


which are used in optical labs and stores, such as Wal-Mart and Lens Crafters. In an ongoing effort to reduce manufacturing costs, the company fo- cused on a drill support produced in its machine shop. “There had to be room for improve-


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ment,” said National Optronics buyer Andy Irvine. “To make just one of these steel parts, the shop was machining four sections separately and screwing them together. We figured there had to be a better way to make the part— perhaps even from another material.” The part supports a drill inside the company’s 7E Edger, an automated three-axis patternless edger used to trim eyeglass lenses to fit a wide range of frame styles. For rimless eyeglasses, the 7E drills tiny screw holes into the lenses. In 2008, Irvine consulted Kirk


Barrett, regional sales manager for Graphicast Inc., Jaffrey, N.H., which has been making various compo- nents for National Optronics since 2006. Using graphite molds, the supplier casts parts from ZA-12, a zinc-aluminum alloy that is harder, stronger and more durable than aluminum, brass, bronze or plastic. Barrett studied the drawings for the


four-piece assembly and suggested National Optronics produce them as a single casting. After back-and-forth design discussions, the two companies agreed on a new design optimized for the casting process. Graphicast pro- duced a prototype and delivered the first actual drill supports in April 2009. Since then, National Optronics has ordered four to five production runs per year, with 50 or 60 parts per run. Graphicast’s graphite mold casting


process is well suited for annual pro- duction runs of 200 to 20,000 parts. For a typical medium-volume production run, the cost to machine each part from


March/april 2011 Metal casting Design & purchasing 47


ational Optronics, Char- lottesville, Va., produces high-precision machines for surfacing and finish- ing plastic eyeglass lenses,


The graphite mold process employed by Graphicast is designed to reduce turbulence in the mold during pouring.


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