This week has been instructive and fun. Molding and casting is an area I am familiarity with. I have used molding/ casting in my sculptural work. My experience includes making plaster molds for clay, making clay molds for plaster and wax, bronze casting through the lost wax method, and other methods.
Where my experience was lacking before this week’s assignment was the use of CNC machining to create a three-dimensional wax model from a parametric form. Now that I have some experience using Fusion 360, I found it fun and instructive to create a four diamond Morningstar form with perfect dimensions.
I created several different iterations of the Morningstar in in different sizes, and can use these as templates that can be scaled for other work, as well. This will serve me later, as I look ahead to my final project.
I brought my image into the CBA shop, excited this time to work with the mini-shopbot. I realized quickly that the 1/8th inch mill would not be able to create the high level of detail I originally sought. Even with the flat bottomed mill, which would be able to give me a more crisp form, I would have to add the detail later in the wax or the molded form with other tools capable of producing a finer point.
I ran into a problem in the shopbot create 3 software as I attempted to create the toolpath for both the rough and finishing cuts. I thought I was ready to cut the form, but the mill kept choosing the "wrong" origin point. I tried three other orientations and it still was not starting at the right place. I asked Tom for help and he showed me where I went wrong. I had unknowingly set the origin point in the middle of the piece, and not at where the x and y meet. Because my piece was so small, and would not take very much time, he suggested that I combine the rough and finishing cuts into one toolpath.
I ran the program and all went well. It didn't run perfectly, however, since the mill path was a bit too close to the edge of the wax. Part of the wall was cut through, but I fixed it with a bit of duct tape so that when pouring the silicone, it would reach the required height.
Once the wax was cut, I proceeded to mix the OOMOO silicone based on the specifications on the package. In my experience, it's important to mix very thoroughly, but without adding extra air bubbles. Since the design has many areas where air bubbles could become trapped, which would create unwanted texture within the mold and final piece. I degassed the liquid thoroughly, both in the cup when it was mixed, and also after it was poured. When I poured the liquid silicone into the mold, I poured it to the side to avoid creating air bubbles and to create movement where air would be pushed out of the mold instead of becoming trapped.
I cleaned up the mold and allowed it to set for about 4 hours. I removed the set mold from the wax and it worked beautifully. I wanted to try it right away at home, so I decided to cast water in the freezer: ice.
Then, I decided to cast clay, since I want to have pieces which could be more permanent than plaster, and can be used in artwork later. It took several iterations to cast the clay successfully.
Because the mold is flexible, the clay had to be just the right consistency. I created 16 final button-like pieces.
I poked a hole in several to aid in their eventual attachment to another surface. Also, to assist the drying process, and also to ensure clean firing, I carved out excess material in the back.
The pieces are now ready for firing and glazing!