3D printing is really good for making custom mold boxes. Model the thing you want molded built into the bottom of a cup which is shaped around the object with the walls only as far away as needed. Then fill the cup with silicone. Pull the silicone out and that's your mold. It uses only as much silicone as you need, rather than wasting a bunch filling up the corners of a square mold box. It's good for things you want to produce and would like to have many copies of the same mold. So print a mold that you will use to make molds. Some times you can pour and cure a mold faster than you can print one.