details DESIGN
The casting process can improve aesthetic appearance and dimensional repeatability, compared to weldments.
• Weld marks diminish the aesthetics of a part and can collect debris. • Weldments can vary dimensionally due to distortion and are process-sensitive based on weld passes, welding speed, current input, weld wire size, etc. Once tooling is fi nalized, the casting process produces consistent dimensions within predicted dimensional tolerances.
• T e welding process involves local melting and solidifi cation, which can lead to microscopic fl aws in the weld joints.
• In the casting process, wall thickness can be fl exible and closely matched to what is required for the design. With a fabrication, wall thickness often is controlled by the plate thickness available in the marketplace.
Cast features, such as cored pockets and corner radii and fi llets, improve manufacturability.
• Fillets and corner radii, as opposed to sharp corners and edges, reduce stress concentration and provide smooth transitions at X, Y, L and T junctions.
• A cored pocket oriented along the parting plane reduces weight.
Jiten Shah is president of Product Development & Analysis (PDA) LLC, Naperville, Ill., and a 25-year casting design and manufacturing veteran.
Sept/Oct 2012 | METAL CASTING DESIGN & PURCHASING | 23
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