Here it is folks. One last blog post, for one last project. Let’s reach for the stars, ey? Well alright then, stars it is, which means we need a rocket ship to get there. So it is that our chess piece would be a rocket, specifically the Saturn V rocket.

The first thing to do was get some 3D prints going. For this, we got us a Saturn V chess piece off of Thingiverse and plopped it into SolidWorks. From there, we also made a CAD of the positive mold in SolidWorks. We didn’t use Meshmixer for any of our edits as the resolution of our exported part from SolidWorks wasn’t as smooth as we would have liked, but that didn’t prove to be a huge stumbling block, since SolidWorks was more than capable of picking up the slack. After the CAD was done, it was just a matter of printing out a 1:1 scale piece. a positive half mold, and making a negative impression of said mold with the silicone.

After that, we had to CNC the other positive mold. Unfortunately, the Shapeoko was not operational, so we had to use the Nomad, which was not compatible with the ¼’ end mill bit. This meant that what would have been a 20-minute cut was shaping up to be 7.5 hours, which did not sound like our ideal Saturday, to put it lightly. However, we found some tables online with different feeds and speeds than the default, and with some finagling of those rates, we were able to cut the time down to 2 hours. That certainly isn’t 20 minutes, but it’s a lot better than 7.5 hours.

Now we just had to actually CNC the mold. We got there one afternoon, ready to roll and we started our cut. It went reasonably well for a while, but the piece eventually started to get pulled off of the bed. Fortunately, we stopped it before the cut got messed up too seriously, and retaped it to the machine bed. Then we saw it almost come loose a second time, and at that point we just added duct tape to the piece as well to hold it down, and this time it stayed down. After that, our cut finished up relatively smoothly, and then it was just a matter of making the negative mold.

After obtaining both mold pieces, we are now ready to cast the chess piece. Combine the two pieces together and wrapped around with a rubber band, now we obtained a complete mold and are ready to cast. We first pour parts A and B of the casting materials into two different cups. Then, we carefully mixed Part A and Part B by weight, using 10 grams of each. Stirring the mix thoroughly, we poured the mix into the prepared mold. This is an extremely exothermic reaction. As the mixing cures, the mold has been significantly heated up.

After obtaining two pure white chess pieces, we decided to add some color to it. As a part of the Duncan family, yellow and green became our choice. By adding the corresponding dye into the mixture, we successfully cast green and yellow chess pieces!

Then, we decided that we could be more creative! How about we add different colors but don’t mix the color with the mixture thoroughly. By doing this we could obtain a nice, flowing pattern on the surface of the casted chess piece. 

After obtaining all the cast pieces, we decided to add some finishing touches. By using an exacto knife, we removed the extra on the edge of the cast. Then, by using sanding papers with an increasing grit (60, 180, 320), we smooth the bottom of the chess piece and make sure all the pieces stand steadily by itself.

Cost Estimation:

Wood: $1

3-d printing: $1

Silicon Mold: $20

Urethane casting resins: $20

Labor: 10hr * 2 * $15/hr = $300

Total: $342