# Castability

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{{Short description|Ease of forming a quality casting}}
'''Castability''' is the ease of forming a quality [casting](/source/casting).<ref name=ravi1/> A very castable part design is easily developed, incurs minimal tooling costs, requires minimal energy, and has few rejections.<ref name=ravi2>Ravi, p. 2</ref>  Castability can refer to a part design or a [material property](/source/material_properties).<ref name=ravi1>Ravi, p. 1</ref>

==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 [undercut](/source/undercut_(manufacturing))s or interior cavities it decreases castability due to tooling complexity. Long thin sections in a design are hard to fill.<ref name=ravi1/> Sudden changes in wall thickness reduce castability because it induces [turbulence](/source/turbulence) during filling; [fillet](/source/fillet_(mechanics))s should be added to avoid this. Annulars in the path of flow should be avoided because they can cause [cold shut](/source/cold_shut)s or [misrun](/source/misrun)s. A design that causes isolated [hot spots](/source/hot_spot_(casting)) decreases castability.<ref name=ravi3/> An ideal design would have progressive [directional solidification](/source/directional_solidification) from the thinnest section to the thickest.<ref name=ravi4>Ravi, p. 4.</ref>

Location of the mold's [parting line](/source/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](/source/surface_finish) or defect free surface it reduces the castability of the part.<ref name=ravi2/> However, the casting process can be very economical for part designs that require intricate contoured surfaces, thickness variations, and internal features.<ref name=ravi3>Ravi, p. 3.</ref>

===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.<ref name=ravi3/>

:<math>\frac{V_c}{V_b}</math>

Where V<sub>c</sub> is the volume of the casting and V<sub>b</sub> is the volume of the smallest box that the casting could fit in.

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

Where V<sub>c</sub> is the volume of the casting and A<sub>c</sub> is the surface area of the casting

:<math>\frac{1}{(1+n_f)^{0.5}}</math>

Where n<sub>f</sub> is the number of features (holes, pockets, slots, bosses, ribs, etc.)

==Material properties==
Material properties that influence their castability include their pouring temperature, [fluidity](/source/Viscosity), solidification [shrinkage](/source/Shrinkage_(casting)), and [slag](/source/slag)/[dross](/source/dross) formation tendencies.<ref name=ravi1/><ref>''Tool and Manufacturing Engineers Handbook'' (TMEH), 4th Edition, Volume 6, ''Design for Manufacturability'', Society of Manufacturing Engineers, 1992.</ref>

==See also==
*[Casting defects](/source/Casting_defects)

==References==
===Notes===
{{reflist}}

===Bibliography===
*{{Citation | first = B. | last = Ravi | title = Design for castability | publisher = IIT Bombay | url = http://www.energymanagertraining.com/foundries/pdf/CDA7.pdf |archiveurl = https://web.archive.org/web/20061210224324/http://www.energymanagertraining.com/foundries/pdf/CDA7.pdf |archivedate = 2006-12-10}}.

Category:Casting (manufacturing)

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Adapted from the Wikipedia article [Castability](https://en.wikipedia.org/wiki/Castability) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Castability?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.