details DESIGN
Adequate radii provide better part defi nition and eliminate the potential for broken mold edges, which lead to sand inclusions in the casting.
• Generous draft, fi llets and radii impact the overall casting surface fi nish and quality of a casting.
• T e casting process allows design engineers the fl exibility for smoother transitions from thicker to thinner sections. Adequate radii and fi llets in varying cross- sectional areas eliminate or reduce the stress concentration eff ects to provide cleaner castings with better component fatigue life in service.
Cast solid and drilled holes
As-cast cored holes
Drilling small holes instead of coring may be more effi cient.
• Depending on the size (diameter, depth and area sec- tion thickness) and location (with reference to the part- ing plane orientation), the design engineer must decide whether to use drilled or as-cast cored features.
• For iron sand castings, typically hole diameters smaller than 0.5 in. and deeper than 0.5 in. are cast solid to be drilled later for wall section thickness of 0.25 in. or more.
• Sometimes, to locate, support and vent the core gasses, cored features are strategically located.
Jiten Shah is president of Product Development & Analysis (PDA) LLC (
www.pda-llc.com), Naperville, Ill., and a 25-year casting design and manufacturing veteran.
Jan/Feb 2015 | METAL CASTING DESIGN & PURCHASING | 17
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