Anvil Casting

This project was completed for 24-672 DIY Design and Fabrication at Carnegie Mellon University.

The prompt for this project was to design and fabricate a small part using 3D printing that could be molded and cast using silicone and resin respectively. During my design process, I kept in mind that the part would have to be moldable, and thus avoided designs with difficult undercuts and overhangs. This steered me toward designing an anvil. Below you can see the master used to create the mold, the mold itself, a raw casting, and a finished casting.


My design process began by sketching possible proportions of my anvil. I then sketched orthographic views from all the distinct sides of the anvil so I would have a reference while CADing the design.


After sketching the design, I moved on to creating the 3D model. For this, I chose to use Fusion360 so I could have more practice, especially with the surface modeling features which I used for the horn of the anvil.


Once I had a 3D model, I could evaluate it for molding. To do this, I used Solidworks’ draft analysis and thickness analysis tools to ensure I did not have any overhangs or features to thin to mold. The draft analysis also verified my planned parting line down the symmetry line of the part would work best.


I also rendered the part using Solidworks.


I was then ready to 3D print and prepare my master part to be molded. I chose to use an SLA printer because I had never used one before but I knew the finish would be of a higher quality than with the FDM printers available to me. Despite the high quality finish of the SLA printer, I still had some sanding to do to get the part smooth and ready to be molded.


With my finished part, I then began the mold making process. First, I prepared to pour the first half of the mold by covering half of the part with clay. This left only areas I wanted captured by the first half of the mold exposed. I also added divots to the clay which would act as registration marks in the final mold. I then created a box around the clay and part so I could pour the silicone.


After the silicone cured, I rebuilt the box so I could pour silicone over the first half of the mold (remembering to leave the part in the first half of the mold and to spray mold release so the silicone didn’t bond to itself). After the second half of the mold cured, I cut out an entry hole for resin. I didn’t need any weep holes due to the simplicity of my part.


I was then ready to start casting parts with resin. The casting process was fairly straightforward. After securing the mold together I poured in resin and waited for it to cure.


After the resin hardened, I was left with a fairly messy part. To finish it up I had to cut off the stem left by the pour hole and sand down the parting line.


Final photos of the different parts: