Minions! | ENGI 210: Prototyping and Fabrication

For this project, we would use multiple techniques to create a mold to cast eight figures. To start this project, we would have to select a figure and prepare it. We decided to go with a minion figure that we thought would work with the CNC and 3D printing aspects of this project. We would CNC half of the minion and 3D print the other half to then make the whole mold of the minion.

To prepare the figure, we modified the STL of the figure by cutting it in half, scaling it, and adding a base around it to make the mold. We also added an extra channel around the minion to help with aligning the mold. Once the file was ready, we could then manufacture the two pieces.

3D printing one half was relatively easy. We sliced the file and sent it to the printer. The print came out really well and it maintained a lot of the detail. We also had to CNC the other half of the minion. To do this, we created a roughing tool pass with a 1/8 in bit and another finishing pass with a 1/32 in bit. This made the CNC cut very detailed.

Next, we would create the mold from these positives we made. We created a box of indeterminate size for the 3D printed part and poured the mold in. We were able to just pour the mold into the CNC part because of the walls around it. The mold from the 3D printed part came out really well. However, the mold from the CNC positive came out with a lot of bubbles and was still moist. We thought this was because of the moisture of the wood and we ended up trying to dry the wood with a heat gun and letting the mold dry for a longer time. This did help a lot and the mold came out much better the second time.

From there, we could cast our minion. After casting the minion, we found out that the liquid plastic had a hard time getting all the way to the tip of the heart. After a lot of testing, we found that the best way to cast the minion was to cast the half with the heart first and then putting the mold together to finish casting the model. This let us cast the whole minion with a lot of detail. We also died the liquid plastic to create different colored minions.