Wow, our last new skill of the semester! It seems like just yesterday we were learning to thread the sewing machines. For our last homework before the final, we tackled CNC milling. We each chose a noun from the Noun Project, and cut it out of a block of wood using the CNC mill. This machine reminds me of a combination of the laser cutter and the water jet cutter. Similar to the engraving settings of the laser cutter, the CNC mill can make pocket cuts of different depths. And it can also make cuts and show you a preview of the machine’s motion, like the water jet cutter, although one difference is that the CNC mill will make several passes in order to cut the full depth of the wood, unlike the water jet cutter.

For my noun, I started out a bit too ambitious. I envisioned cutting out an outline of the United States, with a pocket cut for each state I’ve lived in: Maryland, North Carolina, Wisconsin, and Texas. However, I couldn’t find quite the right file online to work with. One of them looked promising, because it had each state’s shape drawn separately, so I could easily delete the ones I didn’t want. However, it didn’t have an outline of the full country, and when I tried using the path offset in Adobe Illustrator, it made an offset for all of the states individually.

After an hour or so I decided to cut my losses and make a simpler shape: a Texas outline with the Rice “R” in the center. I found an outline of Texas on the Noun Project, and found a Rice logo through Google Images. I then used Illustrator to vectorize the Rice logo and put it in the center of the Texas outline.

Now, onto the cutting itself. I started to set up my toolpaths but realized that the shapes making up the R were too small to be cut with a 1/8″ bit. Unfortunately, I was pressed for time and needed to make some sacrifices to the aesthetic complexity of my design. If I’d had unlimited time, I would have liked to choose the right bits for the R and the intricate outline of Texas. Instead, I made a new, simpler shape, consisting of a geometric flower inside a circle.

I set up my piece of wood using double sided tape after vacuuming and cleaning the machine. When I started the cut, I increased the feed rate since my reservation on the machine was two minutes two short. All was looking good during the pocket cuts but alas, during the contour cut, the bit swerved, caught the tape at the bottom of the wood, and the block started spinning around, so I had to make an emergency stop.

I had to start again with a fresh piece of wood, remeasuring, retaping, and cleaning and initializing the machine again. Thankfully, I was able to stay a little later than my reservation because the next person didn’t show up until later, so I was able to keep the feed rate at the original speed instead of cranking it up, and this time it went much better. After the cut was finished, I broke the tabs and popped out my two circles, then sanded the tops, bottoms, and side edges. Finally, I stained the two pieces with linseed oil.

Cost analysis:

Cost Type	Cost	Price	Source	Quantity	Total
Materials	1×4 Board	$3.32/8 ft	Home Depot	15″	$0.52
	Linseed Oil			Negligible	$0.00
Labor	Prototyping engineer	$37/hr	Bureau of Labor Statistics	3 hr	$111.00
Overhead	Facility cost	Assume $2800 worth of equipment	FinModelsLab	Assume 10% of equipment costs	$280.00
				Total	$391.52