For the Final Project, we made Christmas’s tress chess pieces to welcome the upcoming holiday!
We found an existing Christmas tree Design on Thingiverse and modified it to look like a chess piece. We also added a star on the top of the tree.
We first 3D-printed out the model to see the feasibility of future CNC and size reference. It is a pretty symmetric shape and no overhangs, we decided to proceed with this design.
For the next step, we sliced the model in Meshmixer to reduce and cut it in half , then using solidworks to add the mold base. The tree itself is symmetric, we sliced from the middle line of the star.
We first printed it with using the PLA 3D printer. We printed 2 version. We ended up using the version on the right with a pouring path for the star.
Then, we made a “box of indefinite size” around the 3D printed half for Silicone Molding.
Next, we CNC machined the other half. We had a 3 tries until we got the desired piece.
The first 2 was done using the Shapeokoo as we can use a 1/4 end mill for the roughing path. We used tool path for 1/4 endmill roughing and 1/8 ballmill finish using the default parameter. The roughing took about 45 minute and finish took around 10minute. The result wasn’t good. It was still very rough and we noticed that the finishing drill wasn’t touching the piece until the last 2 minutes of the job.
Above is a Set up picture in the shapeokoo machine. The only way to secure the wood without additional drilling for support is horizontally, so we also had to orient our file and recalculate the tool path.
Because the Shapeokoo wasn’t able to connect to the computer, we used the Nomad for our third trial. Prof.Bisesti kindly help us to optimize the settings. We learnt that the roughing path shouldn’t be long while the finishing path should be longer. For this final trial using Nomad, we used 1/8” endmill for roughing, 1/8” and 1/16” ball mill for finishing. 1/4” endmill is too big to fit in this machine.
Here is a picture of the finished piece using Nomad. It is much cleaner than the other.
This is a comparison with all 3 pieces. Trial 1 to 3 from left to right.
We further sanded the last piece to have a nicer surface for molding.
Again, we created a box around for the silicon pouring.
Last step, casting! We secure the two mold with rubber to prevent leaking. For our first piece, we used the 30min casting solutions for practice.
Our first piece turned out to be off-centered due to the holes not being aligned well.
To trouble shoot, we cut off the connecting holes/support and tried to use our eyes for alignment, and used a marker to mark the alignment on the mold. The results were better but we did do a lot of trials to get the best ones. We also added a few drainage line by simply cutting the mold, to prevent bubble from forming. Below is a picture of possible air bubble that lead to the disconnected parts.
Last last step, Adam post-processed the pieces by
cutting off the bottom extension using a band saw, wet sanded down the surfaces and the split lines using sandpaper and a dremel, and extensively sanded down the bottom to get out final pieces.
clean workspace: used IPA to wipe down the table
Cost Break Down:
Labor: $150
– 15hours x $10/hours
Tools: $0 All shared equipment from OEDK
– Bambu 3D printer
– Shapeokoo Machine
– Solidworks & fusion3d
– Nomad 3D
– Vcarve
Consumable Materials: $22.62
–
PLA: 200grams, $16/1000g -> $3.2
– Cardboard: Reused -> $0
– Silicone: 60ml x2 $23.45/1418ml ->$1.92
Conclusion:
We had a comprehensive view of modeling, molding and casting process. We learned that for CNC machining, we can let the roughing process to be as quick as possible and let the finishing be longer. The orientation of the file and how you set up the wood piece is very important as well. We also learned that when we modify the file in the later step, we should make sure the alignment match. Adding the drainage path to the mold was also helpful. Be flexible and creative in trouble shooting can save the time from doing everything all over again.
