Castability

Part design

Part design and geometry directly affect the castability, with volume, surface area and the number of features being the most important attributes.

If the design has undercuts or interior cavities it decreases castability due to tooling complexity. Long thin sections in a design are hard to fill.

Location of the mold's parting line also affects castability, because a non-planar parting line also increases tooling complexity.

If a design requires a high degree of accuracy, fine surface finish or defect free surface it reduces the castability of the part.

Quantitative analysis

The castability of a design can be partially quantitatively determined by the following three equations. Better castability is denoted by a larger number.

:\frac{V_c}{V_b}

Where Vc is the volume of the casting and Vb is the volume of the smallest box that the casting could fit in.

:\frac{6(V_c)^{2/3}}{A_c}

Where Vc is the volume of the casting and Ac is the surface area of the casting

:\frac{1}{(1+n_f)^{0.5}}

Where nf is the number of features (holes, pockets, slots, bosses, ribs, etc.)

Material properties

Material properties that influence their castability include their pouring temperature, fluidity, solidification shrinkage, and slag/dross formation tendencies.

References

Notes

Bibliography

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References

1. A very castable part design is easily developed, incurs minimal tooling costs, requires minimal energy, and has few rejections.Ravi, p. 2
2. Ravi, p. 1
3. However, the casting process can be very economical for part designs that require intricate contoured surfaces, thickness variations, and internal features.Ravi, p. 3.