part not achievable by machining without increased cost.
Design Iterations
The Westinghouse AP1000® nuclear reactor features a revamped fuel assembly providing improved fuel performance over the previous reactor model.
Once GSC received the com- puter model of the fuel nozzle, its engineering team looked at the part from a perspective of castability as well as machinability, using casting solidification software. GSC Industries provides turnkey, machined complete parts, which is an important perk for Westinghouse as it pushes to stream- line its supply chain. “For cast parts that we then have to send to a machining house, I have to put interim requirements with little knowledge of how it would be machined and be a liaison between the casting and machining house,” Lewis said. “With GSC, who does both casting and machining, I just pass the final require- ments on. Tis gave the casting supplier flexibility to add features or do things differently to improve machinability.” GSC suggested some radii and gussets in the corners, where the part transitions vertically, to improve flow- ability of the wax to make the pattern, as well as the molten metal. “Features like that, we would not
have thought of,” Peterson said. “Radius sizes for castability was a key factor, so the supplier’s input was important.” After reviewing GSC’s suggestions,
Westinghouse approved the design to move through to the next phase, and a rapid prototype was made. GSC used stereolithography to
produce wax patterns from the CAD model then cast the prototype part in CF-3 stainless steel. Te investment caster partially machined the part before shipping it to Westinghouse for load testing. It was one of GSC’s first forays into rapid prototyping. “Out of that, we were able to
receive early prototypes for risk miti- gation,” Lewis said. “In project man- agement, we have a jump-off schedule. In this case, we asked the supplier to develop a contingency process in case the single-piece casting design could not be validated.” For contingency, GSC and West- inghouse designed the wax tool con- figuration in such a way that if the top nozzle could not meet final require-
44 | MODERN CASTING January 2013
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