Who doesn’t love a celtic knot? The plasma cutter. I got so frustrated with it I even wrote a haiku about how much I hate it but that’s a story you will have to get from me in person. A celtic knot should look like this:

The plasma cutter thinks it should look like this:

Naturally I disagreed so we had to do it again, and again, and again. First I tried all male cuts. These were great for the outside but the inside was not so good. Next I split the cuts, the outside was male and the inside was female. This was a bit of a stretch but it made some better results but left some weird barbs. Next I tried online cuts, shifting the arc length of the lead in, going to an online lead in, and rearranging the file. Eventually I got something decent. Just as I was narrowing in on the perfect combination of online, male and female cuts Dr. Wettergreen introduced me to a novel and unquestionably brilliant suggestion. Why not just make it cut along the line and the negative can just be the stroke size of the plasma cutter? Amazingly it showed some promising results but then Murphey’s Law struck. The plasma cutter broke down. Biting my pride, I broke out my best of the 30 million attempts and got to work with a dremel and a grinding bit. After some painstaking and honestly, smelly, work the insides had less ugly barbs and it was time for some post processing.

The first step was to finish up angle grinding off the dross. Then it was into the sand blaster for some HEFTY sand blasting.

After that was complete I did some silver and black spray painting to make it look cool. I tried to give it a texture by pressing sandpaper into it but that was a medium level result. All in all I am proud of the result even if it was not perfect. There are some bumps and burs but its mine and for that I am proud.

Although I encountered some serious frustrations in this project it really taught me how to use the plasma cutter. Little things like the fact that the plasma cutter makes cuts based on the order (back, front, etc.) of the tool paths is really useful information and surprisingly few lab assistants know it. I wanted to challenge myself on this assignment which is why I chose the Celtic knot. The small size really pushes the machine to its limits and that is what I wanted to find. As a result the edges are not as smooth as I would like and frankly my spray painting skills still need a lot of practice but it is a cool looking design and I hope OEDK users enjoy seeing it on the wall of diamonds!

Cost:

Steel: $3

Labor: $10

Total: $13