At this point in the semester, we have reached the final stages of our prototyping training. This is where the fascinating world of CNC machining comes to play and the precision machine yields sub-milimeter tolerances on the final workpiece. That is a marvel of modern manufacturing if you ask me!
The material removal CNCs in the OEDK are the Carvey (located next to the 3D printers) and the X-Carve (which is bigger and is located in room 110 next to the laser cutter room). These machines can run off of g-code produced on CAD software or even websites such as easel. The g-code is essentially a compiled code of work instructions for the machine to follow. It’s responsible for calibrating the axis, maintaining the pre-set plunge rate, feed rate, and depth per pass, it directs the cutting tool on the cut path, and in some cases can control the cutting fluid (for metal CNC operations).
To get my CNC practice going, I started out by searching for a noun from the noun project. Warning: the noun project has the same addictiveness as social media, user discretion is advised. I selected a Charles Darwin noun which was quite intricate but seemed like a simple enough (all credit goes to the creators of each noun included in the image).
I tried using one of the smaller red oak blocks under the ENGI 210 table which required the use of a 0.04″ bit to complete, but the settings I used were not appropriate and ended up breaking the bit. After a bit of searching, I found some leftover wood which would be my new workpiece. The Darwin noun was milled using a 1/16″ fishtail bit, but did not come out as expected. Some cuts merged because the paths were too close together and the material did not withstand the cutting force.
Darwin has seen better days.
I considered using a smaller bit, but instead chose to work on a different noun that would inspire me to troubleshoot more. My quest for the right noun took me in many directions. I searched geometric patterns, wolves, foxes, ferrets, and even Rambo at one point. Nothing appealed to me…until I started to think about my most recent passion: rock climbing!
Before making a final cut with the fancy cedar wood Dr. Wettergreen ordered, I practiced making a cut with the same piece of wood used for the Darwin noun (on the other side). The cut was quite smooth but would still involve some amount of sanding. I was ready to make the real cut on the Cedar.
Forgot to take an image of the final cut, here’s an in-progress image instead…
The Cedar block was not even and the faces were not parallel. To solve this issue some sanding would be necessary. The first face was sanded using the belt sander downstairs and to make the faces parallel I tried using a bubble level on my phone while sanding to get the same angle as when the phone was on the sanding belt (with the machine turned off of course). This process was not very accurate and though I got quite close to making the faces parallel it would be better to use a bench top planer *cough* see below *cough*.
Quiz: Is the machine running or not?
Huh, how’d this get here?
Anyway, the next step was to secure the workpiece on the Carvey and set the appropriate dimensions. I used the rulers on the workplane to get an approximate area for cutting after which it would be crucial to center the design within the desired dimensions (eyeballing was a good strategy here).
My eyes are capable of sub-milimeter precision as well (sometimes…).
I knew Cedar was hard based on a fingernail test so the Hard Maple settings were used and as an added precaution to prevent bit breakage the feed rate, plunge rate, and cut depth were lowered. This would of course increase the cut time (to a total of 1 hour) but I would rather take a longer time than break one of the bits. The final cut was beautiful, the Cedar was a perfect material for CNC work. I also carved my initials using the text feature in easel and a 0.025″bit which took an additional 20 minutes.
An extra touch would really send this project home, this involved darkening the “rock” with some Tung Finishing Oil, staining the rope and chalk bag black with some gel stain, and staining the climber with some gray stain. I used a thin paintbrush to try and avoid staining outside of the cuts but this was inevitable so a final sanding was necessary to get the wood color back.
This was a pretty fun project to send.
The finalized design was perfect, the colors were not extremely vibrant which gave it a “chalky” texture and the “rock” had color variations just like with any geological formation you would find during a day at the Crag (climber slang for outdoor climbing area). I can’t wait to hang this up somewhere, hopefully next to my gear.
