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
One problem I ran into with my award medallion project is how to make metal purple. Because Calontir likes purple. A lot. After digging around, I came up with four possible plans: Enamel Patina Dye-oxide Dyed epoxy Enamel This was my first choice, as it both looks pretty and fits into the time period of the SCA. After some modifications to my soldering station and a promising test on scrap copper, I took one of my newly cast Golden Swan medallions and went to work. A layer of enamel was applied and things looked good. The medallion was set aside to cool. While I was cleaning up other parts of the shop, I started hearing a faint little "Ting! Ting!" coming from the soldering tray. All of the beautiful enamel was popping off! Which lead to the first lesson from this project: coefficient of thermal expansion. I broke off some of the surviving enamel to be able to test other things, like some purple paste wax in the upper right. But you get the idea with the broke