Our fifth ENGI 210 project was an introduction to the plasma cutter and an adventure in post-processing. Starting with a basic diamond shape, we were tasked with modifying the shape in some way, plasma cutting the piece out of metal, and then post-processing the piece for aesthetics. In regards to metalworking, I was like a fish out of water. The most experience I’ve had with metals was one time when I tried to hammer a hole into a thick sheet of aluminum (did not work out well). I was excited to try out some real metalworking tools, and see the sparks fly with the plasma cutter!

Rather fittingly, I chose to plasma cut a fish into my diamond. After browsing some animal outline pictures, I came across an image of a fish skeleton that looked cool, but not overly complicated. I traced the outline of the fish in Adobe Illustrator and converted the file to the dxf format for Torchmate. I plasma cut three aluminum pieces (extra 3rd piece for testing). They all turned out quite well! The vertical lines in the middle of the fish came out much cleaner than I’d expected.

Next, I used the angle grinder to remove the leftover dross and even out the edges of the pieces. The name “angle grinder” seemed intimidating at first, but using it was very much like using an overpowered orbital sander. Luckily with aluminum, grinding the metal doesn’t release any sparks. The angle grinder annihilated all the dross and left the pieces with a satisfying even surface. Of course, no good ENGI 210 project can exist without sanding, and I spent some quality time sanding and filing away at my pieces with medium-high grit sandpaper. I had trouble reaching the inside corners of the fish, but by the time I was done, the edges of the diamond were smooth, and my fingers were sufficiently covered in metal dust.

Grinding and sanding left the surface of the diamonds a bit scratched up. I sandblasted all the diamonds to create a uniform, matte finish, that would serve as a good foundation for spray painting. My first try at sandblasting left the diamond rather spotty-looking, but my sandblasting skills improved with every diamond.

I knew from the start that I wanted to spray paint my diamonds. However, I wanted to try something fancier than a solid color surface. I looked up videos online on different spray painting techniques and thought: wouldn’t it be cool if I combined two colors and did a fade effect? I chose metallic gray and blue as my colors, with gray as the base, and blue as the fading color. After testing with a bunch of paper slips, I realized the true struggle of spray painting. Since I was working with a piece only a few inches across, it was extremely difficult to control the spray and get the exact same result on each.

I’d been spray painting past 7 PM in the afternoon. By the time the sun began to set, I decided to just go for it with my real pieces. I first sprayed on a base coat of silver. After waiting a while, I then layered on the blue. After quite a few mishaps (including: me spraying too intensely with the blue and having to respray the silver, me chipping the paint while sanding, and me dropping two of my pieces on the ground, leaving behind some unpleasant stripes and spots), I finished the initial spray painting process. It was dark enough outside at the time that I could barely tell what color the diamonds were.

Two days later, I spray painted the back of the diamonds silver. I gave them two coats and waited around an hour in between each. When I peeled away the tape I used to protect the front side, the tape stripped away some of the blue on one of the diamonds, and so I had to respray the front piece to replace the lost color.

To add the procedural directions on the back of the piece, I used the laser cutter with help from Liz and useful tips from Grace. To position the laser properly, I first cut out the diamond base into a piece of wood. I placed each diamond inside the diamond-shaped hole (refocusing before each), and reset the laser to position it at the correct origin for etching. I etched the words using the fiber laser at 35 speed, 100 power, and 55 frequency (raster). I initially ran into a problem with the word sizing, but overall, the etching showed up decently.

To finish everything off, I gave my two real diamonds a few coats of clear acrylic spray. The spray made the etching in the back fade a bit. All in all, not too shabby, though I wish I could’ve had another chance at the spray paint and experimented with a way to make the etching appear even more clearly.

Cost Analysis:

• Spray paint – $4/can *2 cans = $8
• Clear acrylic sealer – $7
• Assorted sandpaper – $7
• Aluminum sheet – $11
• Small plywood sheet – $6
• Masking tape – $2
• Cardboard – dig through recycling bin
• Machining – $20/hr * 1 hr (plasma cutting, laser cutting/etching, angle grinding) = $20
• Other labor (sanding, spray painting, waiting for paint to dry) – performed rather unskilledly by free student laborer at OEDK

Total: $61