This week we learned how to CNC. I’ve never had the pleasure to learn this before, so this was probably one of my favorite lessons so far in the class. My trials and tribulations continued into this assignment:

Design

I wanted to create a shallow plate/bowl that I could use to hold my pins and clips. I drew inspiration from this design:

I considered several options (a hexagonal shape, a rectangle with two shallow trays, my name engraved inside) before deciding on my final design. I based this off of time needed to cut and functionality of the final product (I personally don’t like show pieces, and prefer things that actually have a function to them). I ended up deciding on a single shallow tray with a flower engraving from the noun project, which I would fill with colored epoxy.

I created this in Carbide Create, and set the contours and pocket tool paths based on my wood pieces, and set the material to softwood. I used a larger bit (1/4″) for the pocket so it would cut faster, and a 1/8″ bit for the contours. The total time estimated to cut was 32 minutes.

CNC-ing

I was able to send the gcode to the machine quickly. Setting up the machine took a little longer than expected, but I was able to calibrate the machine to the stock material. Then I cut my first piece.

With my first piece complete, I started with the second. This is when I ran into problems. As the second piece was cutting, it started moving around slightly. I was able to catch it early on with the help of Kaira, who happened to be talking with me, and added some tape to the side to provide stability. The piece continued fine, but after a few minutes disengaged from the tape on one side. We stopped it, added fresh tape (we thought the tape wasn’t set properly), then continued the cut. A few minutes later, it disengaged again. This time, we realized that my second stock was of harder wood than the first. On my Carbide Create file, I changed the wood type to hard wood in hopes that it would fix the issues. I also changed the wood piece to a new one. Then I continued the cut. Again, after about 5 minutes, the wood disengaged again. I added some more tape and added some supporting tape on the sides.

At this point I was starting to suspect that the wood was the issue – perhaps it wasn’t adhering to the tape properly? The lab tech wasn’t trained on the CNC yet, and Danny was in a meeting, so I decided to try one more time. I started the cut again and watched to ensure it was working. This time, as the bit cut into the pocket, it started splintering the wood. Here, I was sure the wood was the issue. I got a new piece of wood, similar to my first stock (the softer, lighter-looking wood, maybe it’s pine?). After fixing the parameters on the file, I recalibrated the machine, send the new file, and started again. This time the cut went great.

Post-processing

For post-processing, I used a dremel to cut off the tabs. Then I used 200 and 400 grit sandpaper to smooth the edges. Then, I mixed some epoxy (gorilla glue epoxy) with 1-2 drops of food dye to fill the pockets. I made different batches for each tray because the glue sets quickly, and I ended up messing up the number of dye drops in both batches. One of the trays has a slightly redder flower, but both looks great! Here’s my finished product:

Cost Breakdown

• Wood: $3.38
• Gorilla Glue Epoxy: $5.97
• Sandpaper: $7.99
• Labor: 4 hours * $7/hr = 28

Total: $35.34