Faced with designing a simple part to cut out on the CNC machine, Jerry and I decided to focus on its ability to cut 3D parts, unlike the laser cutter and plasma cutter. The simplest choice seemed to be a series of stacked circles, something like a tiered cake. To accomplish this, we first made a illustrator SVG consisting of concentric circles with 1/8″ (the width of the bit) between them. We then took them to makercam to begin making the toolpaths. The general strategy was to make inside profile cuts on each of the concentric circles, with two circles at a time cut to the same depth. This would give us 4 tiers of 1/4 inch each. The dense nature of the toolpaths meant that the makercam system of toolpath creation was difficult to keep track of. To get around this, we remade our design in Easel, a more user-friendly CAM package. The strategy was the same, and we added a circular hole to the top for some added complexity, and Easel added 4 tabs to keep the piece rigid as it is cut out.

When we exported the gcode and imported it into the flashcut software, everything looked good, so we began our cutting.

The scaling issue we found in class reared its head in this project as well. As seen in the picture below, the 2 cuts for each tier were separated by circular walls of less than 1/16″. This is because the calibration issue causes the CNC machine to cut files at about 110% size. While the size of the project increases, the bit remains the same size, so the gaps between the profile cut paths were bigger than the 1/8″ bit diameter we designed around.

Luckily, we cut this piece out of foam, so remedying the scaling issue was as easy as breaking off the walls and taking an knife to the remainders to clean them up:

If we were to do this project again, we would definitely increase the plunge rate, plunge depth, and feed rates massively. The piece took about 2o minutes to cut when we probably could have gotten it done in 5-10. All in all, though, CNC cutting is very satisfying and yields some very precise products. While more limited than 3D printing, the precision and quality of the final results are worth it.