In undergrad, I had the opportunity to use large 3-axis mills and an Othermill for milling circuitboards but I never used a standard CNC.
To start this assignment, we had online and in-person training which provided an introduction to the programs we would need, Carbide Create, VCarve, and Carbide motion and the Nomad3 desktop CNC. Each of these programs were relatively straight forward to use with some minor troubleshooting and the Nomad3 was a breeze to use. One of the learning outcomes from the training was the importance of knowing when to use an up cut vs down cut bit as an up cut will leave a raw edge.
For my project, I wanted to make a replica of the Sandia Mountains in Ablbuquereuqe, NM. I was able to find an existing .stl on GrabCAD and imported it into vCarve where I set the dimensions for my stock material and the desired starting depth below the top face of the stock for the cut. The most challenging part of this process was orienting the imported .stl. Once I had my file positioned correctly, I generated rough and finishing toolpaths using a ⅛” flat end mill and a ⅛” ball end mill. Then I placed my first stock on the bed and used the bitzero probe to set my zero coordinates in the lower left corner. I swapped the cylindrical probe for the ⅛” flat end mill (down cut) and ran the rough pass which tool ~22 minutes and removed the majority of the material in stacked layers. Next, I switched the bit for the ball end mill and ran the first of the finishing passes ~28 minutes.This pass shaped the curves of the mountains. The final finishing pass was ~16 minutes and added fine detail for the ravines between peaks in the mountains.
After I repeated the above process for my second mountain, I cut both out of the stock carefully with the bandsaw. I finished the sides with the belt sander and following Douglas’ advice tried to remove some of the “fuzz” from the against grain downcuts with a soft t-shirt. To finish, I sealed both pieces with Danish Oil.
The one thing I would have done differently is cutting the part out on the CNC instead of with the bandsaw. My concern was accidentally jamming the bit on the bed (it was harped on when using the mills in undergrad to be very careful to not jam the chucks). While I think my bandsaw efforts were effective, it was more stressful than it needed to be. I also think it would be fun to explore different orientations of the wood to see the impact of the grain and to test hard woods as I used pine.
Cost Analysis: Material Pine 2x4 = $3.25 Danish Oil = $12.98 Total Material = $16.23 Labor @7.25/hr 1hr x prep 2hr x CNC 1hr x post-processing Total Labor = $29 Equipment $15hr/equipment rental Total equipment = $30 Total cost = 75.23
