The Goal:

The goal of this assignment was to create two chess pieces via CNC Machining and molding and casting. We decided to go with the queen, the most powerful piece on the board. After searching around on Thingiverse and some creepy attempts are creating our own designs, we settled on modeling our piece after the bust of the Egyptian Queen Nefertiti.

 

“The Nefertiti Bust is a 3,300-year-old painted limestone bust of Nefertiti, the Great Royal Wife of the Egyptian Pharaoh Akhenaten and one of the most copied works of ancient Egypt. Owing to the work, Nefertiti has become one of the most famous women of the ancient world, and an icon of feminine beauty. The work is believed to have been crafted in 1345 BC by the sculptor Thutmose.”

 

Step 1: Combining Forms with Meshmixer Magic

Using Meshmixer to combine the Nefertiti model stl and the base of another model, I was able to smooth and cut off unwanted parts. Additionally, I greatly reduced the number of triangles as we would not need that many details for our CNC. It took a while to figure out how to edit these meshes and then slice them, but I think the final model turned out well and matches the feel of a chess piece with the circular base.

  

Additionally, we ended up creating the mold design in Tinkercad after having several difficulties in Fusion 360. Tinkercad worked really well and it shows how you can do so much with the simplest of tools.

Step 2: Generating G-Code in Fusion 360

 

After following the tutorials given on Canvas and a lot of pointers from others, we learned a lot of tips on how to set up the model and CAM settings to get an appropriate g-code. The most difficult part was converting the mesh to Brep, which could only by down by turning the object to “do not capture history” before this option for mesh to Brep would pop up. However, once this was figured out we were able to export the g-code easily, using 3D adaptive as our setting.

Step 3: CNC Milling our positive molds

 

Once the code was created we deleted the coolant lines and the other commands that were mentioned on canvas. However, once we started cutting, we soon realized that the orientation of the cut was off and was not cutting the entire image on the block. We were able to achieve better alignment on the second cut but the first one had a significant portion of the head missing on the top. EJ used his hot-glue sculpting skills to complete the image and this worked really well for making our positive molds complete, although our keyholes were not complete and it was clear that alignment would be difficult later on in the process. Each piece took around 2 hours to mill.

Step 4: Creating the Silicone Mold

 

 

Unfortunately, I had to study and take a very important exam, and was not present at this part of creating the lego wall and gluing everything together to ensure the wood did not float to the top. However when I was able to check on it, we found that the mold was still quite sticky although it came of cleanly after we released it from the lego wall and cardboard. However, we ended up modifying our mold a little by cutting off the lips and cutting in the pour spout and alignment keys to match better.

STEP 5: CASTING THE CHESS PIECES

Our final aligned mold with the two halves looked fairly mismatched and it was hard to tell if they were properly aligned. To keep them held in place, we stuck toothpicks through the silicon mold and wrapped rubber bands around to further secure and clamp it into the appropriate position.  

After this we mixed the SmoothOn material, first casting a light one with no dye and then a “black” one made with brown and purple dye. This was then poured into the pour spout and were allowed to set for 30 minutes.

Step 6: Post Processing

It was easy to see that our halves did not align perfectly due to our problems with the positives and having to improvise with hot glue, however it was fairly easy to sand of the edges to make the object look more cohesive and reducing the lip of the seams. We did this by breaking off the pour spout and parts, sanding off parts, and using a dremel on the low setting. After this we just rinsed off the resulting dust and then sprayed a coat of clear gloss over the objects giving them a nice finished look.

 

Final Results and Conclusion

Overall, I enjoyed the process of creating our chess pieces, although I was initially worried that we would not be able to create a mold quickly enough. The SmoothOn products and Oomoo used were pretty easy to use once we learned some tricks, and I definitely understand some better ways to create molds in the future which will come in handy for the Willy Statue project and anything else. I also look forward to seeing how the final chess set turns out and hope that it can be completed and played with!

I think that molding and casting is a very useful technique and enjoyed working on it via CNC milling. I have learnt about traditional (Thai) lost wax casting in the past to make jewelry pieces, carving wax blocks with various tools and then casting in plaster before being able to make metal jewelry that can be processed, so it was interesting to see how this process can be adapted to this situation, using a mill instead to create the block with (relatively) little labor. The equivalent process by hand took several days to carve a tiny block of wax through the use of various dental tools and an overhead magnifying glass to create the form and perfect every detail of the positive form. Although the details would be more intricate this way, I am sure a similar effect could be produced with a combination of the processes and the use of smaller bits for fine details.

In the end, this was a good way to end the semester, learning more techniques that will come in handy for other things I may want to make and the best ways to do so. I definitely gained a greater appreciation for the way manufacturing works and the procedures and decisions that go into making an object the best it can be and improving my skills to do so.