innovations CASTING
Engineering Turns On Switchgear Design
limited. The 38-lb. lower connector was to be made in pure electrolytic copper because it requires a minimum International Annealed Copper standard for electrical conductivity of 98%. With a projected volume of 250
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pieces, the manufacturing options were to either machine it from a large piece of copper and bolt on sections to add the cooling fi ns, or cast it in the permanent mold process. Powell opted to cast the part, but the method was not without its challenges. T e cast design featured 15 heat- dissipating fi ns, four elongated slots for air fl ow, a cast hole machined to accept mating parts, three mounting surfaces and a large cast diameter on one end machined to accept a connector. The electrical systems manu-
facturer turned to Piad Precision Casting, Greensburg, Pa., to tackle the component. Although the CO11 copper casting went beyond the cast- ing supplier’s typical size envelope, Piad took on the job and adjusted its casting equipment to handle the hefty part. The pour weight of the casting with the gate is more than 50 lbs., 25% more than the largest component Piad previously produced. “We really wanted to stretch our
capabilities for the project and say we could do it,” said Karl Schweisthal, retired CEO and current consultant for Piad. “Our permanent mold process was the only game in town, or else they’d have to fabricate it. It would mean taking a block of copper, which would have been twice the weight, and machine all the details. It would have been horrendously expensive.” T e metalcaster worked closely with engineers at Powell to adjust the design for improved castability. T e electrical systems company provided Piad with requirements for weight, material prop- erties and functionally-critical geomet- ric features. Based on the requirements
Sept/Oct 2011 | METAL CASTING DESIGN & PURCHASING | 49
he manufacturing methods for a Powlvac switchgear component from Powell Industries, Houston, Texas, were
The large diameter at the end of the switchgear was machined to accept a connector.
of the customer and the capabilities of its casting operations, Piad suggested several design changes. Piad needed a pouring channel in
the part to prevent the metal from splashing into sections, which could cause cold fl ow issues. It suggested moving the air fl ow slots further to the
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