CNC literally means computer numerical control. In this context, CNC refers to a computer operated drill bit that operates in multiple axes. Like a 3D printer, it uses gcode, but subtracts rather than adds material. For this assignment, we use a Carvey, a 3-axis desktop CNC for small projects.

NOTE FOR GRADER: MY PROJECT IS NUMBER 13

choosing a design

Here are the three options I picked out. Looking through past projects, I discovered that the mountains had already been done, or at least something very similar, and repeats are boring. The lavender looked like the small gaps were going to be too delicate to not be broken when milling, at least at a reasonable mill speed, so I went with the tree. I then imported it to Adobe Illustrator, sizing it as I liked, and exporting it as an SVG.

          

preparing the Cut

First, I got my piece of wood and measured it. Being about 5.5 x 4.5, I realized that if I wanted two parts on one piece of wood, they’d have to be pretty small to fit without the mill hitting the clamp. Using easel, I made sure the designs were close enough that the outlines could share an edge. The outline is 1/8 inch so that the drill bit can go all the way through without breaking, and the design itself uses a 1/16 drill bit to maintain fine details. 

cutting

First I clamped down the piece of wood, adding an extra piece underneath so that the drill bit wouldn’t damage the base of the Carvey. I added an extra clamp on the side and installed the 1/16th inch bit. It took 3 minutes. Then, after vacuuming and a quick visual inspection, I installed the 1/8th inch bit. This one didn’t fit a fan so it was harder to get a visual on how the cut was doing. The outline took ten minutes.

post processing

Fresh off the Carvey, the parts had very jagged edges. I sanded the edges, starting rough and working my way smoother. I considered staining the wood, but I liked its natural color and I didn’t want to add a finish due to my lack of experience using finish.

cost analysis

The wood: oak currently running at $0.064 per cubic inches at lowes, my 18.35 cubic inch block cost $1.17

The machine: at $40 per hour in maintenance, my 13 minutes of machine time cost $8.67

The sanding: at $3 for five sheets, I probably used up a total of a quarter sheet, or $0.15 worth of sandpaper

The time: Since sitting and watching the machine was not an active use of my time, I only count the 30 minutes of sanding and the 15 minutes of file prep. At my rate of $21 an hour, that’s $15.75

In total, this project cost $9.99 before labor and $25.74 after.