When discussing metal post-processing techniques in class, what most caught my eye was the sleek, elegant finish attained through sandblasting. Learning that sandblasting is the surface treatment that Apple applies to their products didn’t surprise me at all, as Apple products exude this same characteristic sleekness. So when it came to creating my design to plasma cut, I tried to think of what would look classy and smooth when coupled with the texture of bare sandblasted metal. Deciding that Yin and Yang would be perfect, I got to work in Illustrator.

I quickly realized that, in cutting a Yin and Yang-shaped hole out of my diamond, leaving the characteristic dots in the center of each side would be a challenge. However, my pumpkin-carving instincts kicked in, and I moved the dots outward so that they overlapped with the edge of the shape, allowing them to not be cut out. In the likely event that none of that made any sense, my initial Yin and Yang design can be seen on the right for reference.

There were a few problems with this initial Illustrator design, though. For one, I had created it in a somewhat free-handed manner, leaving something to be desired in the precision department. More specifically, the line through the center of the shape had horribly varying widths, and the points of the shape’s two sides were both far too sharp. As such, now that I had the general idea in mind, I began a second attempt.

This time, as shown on the left, I traced a thick, uniform curve to ensure the neatness of my design’s center line. This resulted in a much neater design, which I ultimately used to plasma cut. The final Illustrator design is shown below and can be downloaded here.

Next was plasma cutting, which was surprisingly simple. Importing a DXF version of my file into Torchmate, I added cutting paths, ensured that the inside paths would be cut before the outside path, and proceeded to cut. Even though I only needed to present two parts as my final product, I went ahead and cut four so as to make room for mistakes. After our ENGI 200 group’s failed attempt to plasma cut gears last spring, I was expecting the plasma cutter to fumble with any lines that weren’t simply straight. However, as you can see below, my cuts were remarkably clean.

I then used the angle grinder to remove the slag from my plasma-cut pieces. Obtaining uniform, clean edges was a surprisingly lengthy process, but it resulted in my diamonds looking much nicer. However, the inner edges of my parts were mostly inaccessible to the angle grinder, so I had to use a hand file to deburr the interior of my Yin and Yang shapes. Afterwards, all of the edges of my diamonds were nice and smooth, except for a couple of rough patches where the plasma beam began and finished cutting the edge. While detracting from the diamonds’ appearance to some extent, these defects are, as we learned in class, an integral part of using the plasma cutter.

Next, I took a wire brush to my diamonds in order to see how nicely I could polish them. While I intended to sandblast my parts, I had been toying with the idea of leaving some sections un-sandblasted, and I wanted to see how those sections would look. I wasn’t particularly satisfied with the result, however, so it appeared that simple, uniform, and elegant was still the name of the game.

Proceeding to the sandblaster, I meticulously blasted both faces each diamond until they all had the same, clean finish. After turning off and unplugging the sandblaster, however, I realized that the edges of each part were still somewhat shiny, so I plugged the device back in and blasted the edges, too. Finally, each diamond had achieved the same characteristic sandblasted texture all over. After unplugging the sandblaster and removing the diamonds, I noticed that they were still covered in tiny sand particles, so I decided to wash them off in the sink and dry them with paper towels. More on this decision later.

When it came to labeling the diamonds with my name and the post-processing techniques I used, I took it as an opportunity to make a sticker using the vinyl cutter. However, the Yin and Yang holes in my parts left little room on which to attach stickers, so the text would have to be very small. I ultimately cut two sets of stickers on the vinyl cutter, but despite my efforts to use space effectively and cleanly remove the letter-shaped holes from the stickers, they were not particularly legible. I concluded that I would achieve a much more readable (and time-effective) result if I simply printed the contents of the stickers onto paper and stuck that onto the backs of the diamonds. Still, my venture into the realm of vinyl cutting was an interesting and educational one. Below is a picture of the better of my two sticker iterations.

By the time I finished this vinyl cutting venture, it had already been three days since I had sandblasted my diamonds. It wasn’t until this third day that a noticeable grime had suddenly begun to cover my precious diamonds, which worried me. I tried to clean it off, but I quickly realized that this was no ordinary dirt; this was the beginnings of a rust takeover. I cursed myself for having naïvely washed my sandblasted diamonds in the sink three days before, and I resolved to give them a second sandblasting, this time cleaning them in a moisture-free manner. I also decided to explore the possibility of using a clear coat of spray paint as protection against oxidation.

Luckily, after a brief second sandblasting, my diamonds regained the same pristine finish as they had previously. This time, I was sure to wipe them off with a dry rag. I then grabbed a can of clear spray paint to test on one of my diamonds, hoping to assess the effect created by a clear coat. After the first coat, I was concerned that the surface had become somewhat bumpy, but upon applying two more coats the surface smoothed out. However, when comparing the painted and unpainted diamonds side-by-side, I liked the unpainted aesthetic much better. As seen the photograph, the clear coat had darkened my diamond to a considerable degree, and its surface had become significantly more speckled. Looking at the painted version up close, it wasn’t even particularly clear that it had been sandblasted. This version had missed the mark on that sleek, Apple-product-like appearance that I had set out to accomplish. Thus, considering that my diamond will ultimately be hung indoors and shouldn’t be getting wet again anytime soon, I opted for the bare sandblasted version. After all, the protection afforded by the clear paint coat was not so necessary as to justify giving up my aesthetic goals for the project.

Finally, I printed my labels on ordinary paper rather than vinyl stickers, and I cut them out to adhere to the backs of my two favorite diamonds. In my process steps, I included (1) plasma cutting, (2) angle grinding, (3) filing the inner edges, and (4) sandblasting. I decided not to include wire brushing because, while it was indeed a step I performed, it was essentially undone by the sandblasting step. I attached these labels with scrapbooking squares, as seen on the right, to ensure that they achieved a good stick along every edge. At last, my Yin and Yang diamonds were complete, and I turned them in on the ENGI 210 table. My final two parts can be seen below.