Injection molded and sand cast parts require a high rate of flow and the maintenance of temperatures above the glass transition to fill their molds. If the material cools before the mold is filled, shrink cavities and distortions of the part can occur. The most common way to deal with this is to keep parts small, with thin walls and oriented such that the material doesn't have far to travel. Might there be a way around this? Could it be possible to heat the walls of the mold to maintain high internal temperatures until the material has filled the mold entirely? I don't have a foundry to try this myself, but I would love to see someone experiment with heating a sand mold while casting aluminum to see if it reduces or eliminates problems with shrink cavities. Any additional control that we can get over the cooling process can only help, right?