First try for the investment casting process, and I learned from what happened
Step 1: How to Make the Design
First of all, the design I decided to make has been too small for a nice experiment, this is why according to what I do, I know what to improve for next time. I decided to make a paper boat without making too much overhang. I needed to try a simple shape first. You need to create your 3D file, and then 3D print it.
Step 2: The Molding
To pour the metal, you need a mold. Usually it is better to have a model made out of polystyrene because you don't need to take out your model from the mold. However, because we 3D printed the model out of PLA, the material and the shape of the model force us to make a mold in 2 parts. You need to fully fill the 1st box with green sand and hammer it to have a very strong pavement. Then you press your model in the sand, and finally fill the upper part of the box to fully cover the model. Once it is done, you have to remove the 2 plastic parts, and close the mold.
After that, you need to dig a first tunnel to the model shape in the sand to pour the metal, and another one to let escape the gas from the other side. If your tunnel is not large enough, the metal will cool down too fast and won't have time to reach the entire form. (And this is when I realized that my model was to small considering the sice of the tunnel.
Step 3: Pouring the Metal
Once everyting is set up and the Alumium hot enough to be easily poured (aluminum melting temperature: 660°), you need safe equipment to pour it into the holes. You could encounter accuracy problems while pouring the liquid metal depending on which kind of equipment you use.
Step 4: When It Comes Out
Once it cooled down and is solid, you need to manipulate the object with a clamp and put it under cold water 1 or 2 minutes to not burn your hands. In my case the model was to small, so as we can the tunnel is even bigger than the model it self, but thinking about it, it can also be part of the design. So if I can give you an advice, when you make your design you can think about where will be the tunnel and why not integrate it in your design to avoid too much work afterwards.
After sanding it in different directions I obtained different results and gave a different aspect to the metal. (mat) And we can also see the lines of the sanding process on thedifferent sides of the metallic obect. Next step; think Of a bigger paper boat to integrate more easily the mast to it. I also would like to try to fill it entirely to avoid the holes that we see in the middle.