Sand Casting Design Review - Engineers Edge

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Sand Casting Design Review

Design sand castings shapes using the minimum wall thickness required to achieve the strength and rigidity requirements.  The component shape should have gradual and progressive blends in any area that requires section thickness change. Minimalize the number of section changes as blended sections with tapers reduce stress concentrations. Design to avoid isolated or concentrated heavy sections.

The design of cast parts can be improved by avoiding heavy sections. Heavy sections can induce stress concentrations and tears. Design to avoid sharp corners and sharp re-entrant angles. The cooling characteristics of the casting and the molding casts are a major factor in the production of cast parts. Design of corners can have a major producibility influence. Sharp corners induce high thermal gradients. Hot spots are caused by re-entrant angles. Corners produce differential cooling rates. Shrinkage, tears and distortion defects can occur. Design junctions to avoid heavy mass concentrations. Much of he benefits with cast components are achieved by producing near net shaped parts which can involve numerous and often complex junctions. Junctions between sections create mass concentrations.

In the production of the sand cast shapes, a knowledge of the finished part dimensional requirements is desirable to achieve near net dimensions at optimum cost. It is important for the designer to apply as high a tolerance as possible. Specify geometric tolerances such as profile of a surface for complex blended surfaces. Define practical datum targets for post manufacturing processes and inspection. When identifying any jigging or fixture points, design these areas away from any natural line of symmetry or the cast component parting line.

As always, consult and work with the casting manufacturer to improve the component producibility as quality of design.