Intro

So far, I must say, using the plasma cutter has been my most satisfying experience so far. Through the course of this project, I was able to craft my own illustrator design for the first time, and promptly see it turned into an extremely tangible, permanent piece of metal in only a few short minutes. By doing so, I have certainly expanded my prototyping tool library, and I have done so in a way that allows me to produce serious steel parts.

The Drawing

For this project, I decided to take the given diamond and attempt to craft something with personal meaning. So, I took a picture of Tennessee from the internet, turned it into a series of lines, set it in the middle of the diamond, then proceeded to ‘suspend’ it in the middle via 4 thin pieces of uncut steel. In order to make this shape work successfully with the plasma cutter, I had to google and watch more youtube videos on Illustrator. The key tool I found was that in order for drawn shapes to actually be recognized as closed, you have to go to ‘object–>path–>create path’ with your chosen lines, and only then do they actually become a single closed path. This took me a long time to figure out, but I have now been able to craft a few personalized shapes using this technique in Illustrator!

the cutting

At this point, all I had to do was follow the PDF instruction manual for the plasma cutter, and soon I had my shapes! I actually played around a little bit, trying speeds of 130, 100, and 90 and also trying lowering the amount of air delivered on the 90 (on the advice of Joe) which actually resulted in the cleanest lines and least slag! Below are some images of this process and a few of the results:

Note the slag on these particular pieces, along with the large amount of rust. To make these look significantly better, I moved on to the second half of the homework:

Post-Processing

Step one of this process was to remove all of the slag (of varying amounts on different pieces). This process was completed outside, and is shown below. (PPE is crucial for this process given the large amount of sparks produced)

For this process, I angle ground the backside of all of my shapes, removing all slag and rusty exterior. I then angle ground the front of only some of the shapes, as I had cut about 8 of them and wanted to try different finishing techniques. Below, you can see the comparison of an angle ground surface with a reverse side that has not been angle ground (albeit the front side does not have any slag, so everything is surface imperfections.)

I really liked the look of the rust, and this features heavily into my further post-processing.

At this point I decided to file the outside edges of the shapes to remove sharp plasma cut edges. This was accomplished quickly and easily using a hand file, as I only filed enough to remove sharpness, and went no further. In addition, I used fine grit sandpaper to remove the course angle grinder marks seen in the image above, and additionally removed the surface rust on the front edges of those pieces which I only angle ground on one side. This is all seen below (key lesson learned: by wrapping the sandpaper around a small wooden block I was able to sand much more efficiently than by using my finger alone.)

It was at this point that I decided that even fine grit sandpaper left too irregular of a finish for my tastes, so I settled on a sandblasted finish for the outside edges. For the TN shape, I actually decided to either A.) leave the rusty finish if I hadn’t already removed it or B.) promote rust on it. To isolate this portion from sandblasting, I completely covered the center with tape (both electrical and masking, but masking seems to work most effectively) and sandblasted heavily. Before and after pictures of this process are included below:

Note how all streaks and irregular markings have been removed around the edges. I really like this look, and think it contrasts well with the ‘unfinished’ natural coating on the inside. Sadly, this sandblasted steel outside edge was still unprotected, so to prevent rust from forming here I retaped the TN and applied a liberal coating of oil: (note, this definitely worked at preventing rust, but I later had to sandblast it all off again which will be detailed below.)

This process was also completed on the other pieces which I had angle ground on both sides. For these, I continually applied a little bit of water every day, trying to grow my own rusty coating. As you will see, this coating is nowhere near uniform, but is well on its way to getting there!

Surface coating

In order to finalize my process and permanently prevent rust from forming on the sandblasted, outside edge of the diamond, I decided to apply a clear coat over this portion (leaving the center unprotected, again to allow rust to grow happily). Upon reading the instructions on the can, however, I was dismayed to learn that the coating requires a dry, oil free surface for adhesion, and so I laboriously re-taped every single piece, and re-sandblasted all outside edges to remove any traces of oil or rust. At this point I was able to leave the TN taped, and over the course of an hour or so apply clear coat layers to each side of the diamond (2 coats per side.) With this completed, the only thing I had left to do was remove the tape!

final steps

At this point I was left with three of the ‘natural’ rust examples and 2 of the ‘homegrown’ rust, and I decided that the two homegrown ones would be my final pieces, in order to demonstrate more completed post processing steps. Even as I am writing this I have added water yet again, hoping that I will have more complete rust coverage, but as of now it is spotty at best. Perhaps this is something that will develop with time, but even so I am satisfied with the current look. For the three ‘natural’ cases I applied yet another clear coat layer over the TN as well, sealing the look permanently (you can see the ‘shine’ from the clear coat in the picture below.)

For the two ‘final’ pieces I left the TN uncoated to allow rust to continuously develop, made an illustrator file detailing all of my steps, laser cut it, and affixed it to the steel using hot glue. With that, I have completed the homework and taught myself innumerable minor lessons about working with carbon steel, plasma cutting, and finishing techniques! The final pieces are shown below: