Now that we have some wax models from the injection molds , it's time to turn them into metal. I do investment casting, which uses a gypsum "investment" to make the mold around wax models, which are then melted out. This is opposed to other forms like sand casting, where green sand (not literally green, but a fine sand that has been mixed with a binder, like water and bentonite clay for traditional green sand or oil to make petrobond) is packed into a frame around a model, then the mold is separated and the model gets removed by hand. At a high level, there are four phases of investment casting: Mold making Burnout Casting Cleanup Phase 1: Mold Making The first step in mold making is to create a "sprue tree." Essentially, you're creating a system of pipes to deliver molten metal to your models. An incorrectly sprued model can get casting defects. If the sprue connected to the model is too small, the metal in the tube will solidify before the