This empirical equation states that solidification time is proportional to the square of the ratio of a casting's volume to its surface area. Foundry engineers use it to size and place risers, ensuring the feeding reservoir stays liquid longer than the main casting to prevent shrinkage voids. The formula accounts for the metal's thermal properties and the mold material through a specific mold constant.
Heard on the job
Bump up the riser diameter so Chvorinov's rule gives us enough solidification time to feed that heavy section before it freezes off.
Insider tip
Rookies often forget that internal corners heat up the mold locally, changing the effective cooling rate and throwing off a basic Chvorinov calculation.