Firstly, the application of 3D printing technologies in the foundry sector are profoundly reviewed. 3D printing has the potential to supplement or partially replace the casting method. Some castings can be directly printed by metal powders, for example, titanium alloy, nickel alloys and steel parts. Meanwhile, 3D printing has found an unique position in other casting aspects as well, such as printing the wax pattern, ceramic shell, sand core, sand mould, etc. Most importantly, 3D printing is not just a manufacturing method, it will also revolutionize the design of products, assemblies and parts, such as casting, pattern, core, mould and shell in casting production. A skeletal mold structure for castings was proposed, which includes truss-shell mold and rib enforced mold. This structure gives more space and flexibility for the cooling structure design of local areas. The experimental results are given to prove the advanages of this innovative mold design.