For our final assignment, we had to use many skills to develop both a black and a white chess piece. Each group got to choose their own piece, so we would have a full set at the end. We decided to do the knight because, while we knew it would be a bit more difficult, we liked the shape and knew we could find a cool design.

The first thing we had to do was search the internet to find a CAD file to use for the milling. One of the things we were specifically looking for was one where the ears were not free floating because we knew this would cause complications in the CNC milling. We found a nice one on GrabCad, shown below.

Next, we had to bring our file into Fusion 360 and slice it into its two halves. Since the knight isn’t radially symmetric, we had to do two different cuts: one for the left side, and one for the right. We used tools within Fusion 360 to cut and reorient the knight, and then used the CAM portion of the software to create the tool path for the CNC machine. We also added slots for one side, and attachments for the other side so the mold would fit together as well as a block on the bottom to pour the plastic.

  

 

 

 

The next step was to export the tool path. One thing we had to fix was making the origin on the correct spot. This took some time, but we eventually figured it out. To export the tool path itself, we had to download the easel post processor and then export it. In order to make sure it would run, we opened it in easel and it since it looked good, we began to cut it. We used a 1/8″ ball mill and the run took about 1 hour for the right side and 30 minutes for the left. We aren’t completely sure why the left was so much faster, but they both turned out well.

 

Once we had the CNC finished, we had to create the mold. We started by using something called Encapso. It was a clear plastic that was supposed to be good to mold.

Unfortunately, it didn’t work. When we tried to pull it out of the mold, it broke into crumbly pieces:

  

We also realized that the walls on our mold would make it difficult to use. At this point, we cut off the walls and surrounded it with legos. We then poured oomoo around the mold with the hope of it being a better material.

 

About an hour after we poured the oomoo, we got a message from Vidya. She told us that something was wrong with our mold. Our CNC positive had sunk up to the top of the oomoo, so we had to fix it. We waited for it to all dry, then peeled it off the positive and rigged up a device using legos to keep it from floating up.

 

We waited for it to cure, and then were able to peel the oomoo off the positive. It turned out like we wanted, so we were then ready to mold. We used Q300 plastic mold and it dried very quickly. We had some problems getting the mold aligned, so we tried various methods, such as poking in toothpicks, to try to align it. Eventually, we decided we were probably going to just have to do some sanding after the mold had set. We made our two models, then spray painted one of them to be black. We had finally finished, and it felt like a huge accomplishment to do what we did.

 

Overall, this project was a lot of trial and error. We failed several times, but we kept trying to better the process, and ended up with some really cool pieces. This final was certainly a culmination of everything we had learned throughout the semester, and a great way to end the class on a high note.