Our next assignment was to use the CNC machine to cut out a shape of our choosing from a block of wood. The first thing I had to do was decide on my shape. I browsed the Noun Project and eventually decided I would cut out a football. I downloaded my shape as an SVG and saved it for later use.

I first cut two 6-inch pieces of 1”x4” wood. This would give me plenty of room along the x-axis to position my shape. I wanted a two-color look to my piece, so I applied spray paint to the wood before cutting. My idea was that the pocket-cut areas would have a raw wood color while the rest would have my dark green paint color.

 

I then went to the OEDK. I pulled up my saved SVG file and uploaded it into carbide create. After rotating it, I resized it to be 3” along its minor axis and roughly 4.5” along its major axis.

 

I then set my pocket and contour cuts. For the pocket, I did a 0.1” deep cut for everything besides the laces, stripes, and a border around the edge. For the contour cut, I cut the outline, with the tool offset set to cut outside my shape.

 

Once all of this was done, I saved my toolpath and uploaded it into Carbide Motion. I firmly secured my wood piece to the bed of the machine using double-sided tape. I then used the calibration tool to set the machine’s zero. I jogged the machine until it was aligned with the tool, then probed to find the precise zero. Once this was done I was ready to cut.

 

The job started smoothly and ran well overall. I encountered a couple problems, however, and they may have had the same cause. The first problem was my piece shifting during cutting. For the first 10 minutes or so, it held solidly in place, but then I began seeing it wiggle as the tool moved around. I paused the cut, completely removed the wood, applied new tape, and placed it back down. It again was still for a few minutes than began to wiggle again. I replaced the tape one final time and slowed the machine speed down to 70%, and the piece no longer wiggled. This issue resulted in some ugly and uneven cut lines, which are apparent in the final photos.

 

The second issue was the edges of my piece after I was done cutting. They were very ugly, with wood sticking up and out of every edge. Dr. Wettergreen saw this and helped me see what the problem had been — I was using an up-cut bit rather than a down-cut bit. The up-cut bit is good for cutting materials like PVC and plastic, but the down-cut bit produces a much cleaner cut in wood. The up-cut bit sort of rips the wood outwards, resulting in the frayed, splintered edges I see in my piece. I realized this upward direction of the bitting may have also been exerting an upward force on my piece, loosening the tape’s grip. This would help explain why my piece slowly loosened over time more than I had expected.

 

Because of this rough edges, I had to sand down the entirety of my piece. Unfortunately, this nullified the paint effect I was going for since I had to sand it down. This sanding did, however, clean up my upper edges. Some of the pocket cut was not very smooth, but it was not accessible to the electric sander. I tried my best to get it cleaned up with sandpaper, but evidence of the two issues I experienced is still very visible.

 

While I am not ecstatic about the quality of my pieces, I feel that I learned valuable lessons to aid my future CNC machine usage. In that spirit, I finished my pieces with a clear coat of polyurethane, leaving all of the imperfections visible while still applying a glossy, appealing finish.

 

The total cost of producing my part came out to $66.30.