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I know what pattern draft is and it's usefulness in removing castings from rigid moulds. That's the definition you can find anywhere.

My problem is when you sand cast. Sand casting is the most common amateur metal casting technique, with lots of YouTube examples. Yet all the decent examples have a draft incorporated. Since you destroy the sand mould when extracting the casting, I can't see any benefit from a draft. It just adds an unnecessary level of complexity when designing and making the pattern. Any shape could be successfully removed, so what's the point of pattern draft in sand casting?

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You need pattern draft to be able to remove the pattern from the sand before pouring. If you don't have any / sufficient draft then edges can be weakened or damaged / broken when you remove the pattern from the sand or plaster - whatever material it is. It is not to help remove the casting as the sand mould is destroyed.

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  • $\begingroup$ True. However, it is possible that the mould is made in a different way. For example the mould shape may be done by a robot directly shaping the sand or the pattern made out of wax in a 3D printer that will then evaporate when the mould is poured. $\endgroup$
    – joojaa
    May 21 '17 at 20:54
  • $\begingroup$ @PaulUszak was your comment intended for Solar Mike or for joojaa? $\endgroup$
    – zipzit
    May 22 '17 at 1:26
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    $\begingroup$ @joojaa In castings done by lost wax or lost foam, you will find that they are not obliged to have a draft. However, these techniques are more expensive, and are only used when warranted (such as when a draft would interfere with the design). $\endgroup$
    – Cort Ammon
    May 22 '17 at 3:11
  • $\begingroup$ @engineer you linking that post to this answer just shows off your knowledge. $\endgroup$
    – Solar Mike
    Jun 8 '20 at 18:51

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