details DESIGN


Casting exhibits excellent surface fi nish in performance-affecting areas of the pump (e.g. volute and passages).


• T e foam pattern is coated with fi ne refractory coating, providing a smooth surface fi nish. In most cases, the as-cast surface is adequate and eliminates the secondary machining operation.


• Actual as-cast surface fi nish depends on the alloy, process parameters, overall casting size, section thickness, and gating and riser design.


Minimal draft features optimize casting weight.


• Since the foam is fl exible and compressible to some extent, the pattern can be drawn with minimal draft. Zero or negative draft also is possible, depending on the feature depth and location of the foam tooling parting plane.


Jiten Shah is president of Product Development & Analysis (PDA) LLC, Naperville, Ill., and a 25-year casting design and manufacturing veteran.


Nov/Dec 2011 | METAL CASTING DESIGN & PURCHASING | 25


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