Hey y’all,

For the 4th assignment the task was to plasma cut and post process the first state you lived in the U.S. In my case it was Texas.

The process involves creating an electric arc between the plasma cutter and the work piece. The electric arc ionizes the gas blown by the nozzle toward the piece, creating an electrically conductive channel of ionized gas i.e. plasma. The heat generated by the electricity traveling down the plasma melts the material, at the same time, the compressed gas blow the hot molten metal away. To learn more about plasma cutting click here.

Post processing are the manufacturing processes applied to a piece after the first stage of fabrication. It includes processes aimed to smooth the surfaces and edges of the part, eliminating possible imperfections caused by the manufacturing process, such as slag, or imperfections from the material, such as rust or stains. It also includes the painting and coating of the part, to protect it against corrosion. Post processing also intents to make the part more aesthetically pleasing.

The first step was to download a Texas map vector file and delete all text, unnecessary lines and filling in the map. Then we switched to the Torchmate software to create the tool path for our part. Here I and my partner, Brian, found the first problem: every time we tried to create the toolpath the software would crash. After trying to fix it during 2 hours, we tried to create the tool path for the Colorado state and it worked, therefore we concluded the problem was on the Texas vector file.

We talked to Dr. Wettergreen and explained the problem, after finding another Texas vector file he was able to generate the toolpath and fix our problem. However our time on the plasma cutter was gone, so we called it a day and agreed on another time to come back and cut the piece.

With the fixed file, we were finally able to create the tool path of the plasma cutter in the Torchmate software. Then we exported the file to the equipment, set everything up and cut the pieces. No problems this time, both ones looked very good, despite the slang and some rust.

 

One noticeable thing about plasma cutting is that this process is less precise than laser cutting. After creating the tool path we noticed it was not equal to the original shape, it was an simplified approximation, since the tool could not create all the details. In addition, the cut shape had very rough edges and some level of imprecision on the shape, due to the slag.

Now the post processing starts. My goal with this part is to make it aesthetically pleasing but keep the metallic look to show the material it is made of.

The next step was to remove the slag from the edges, which was done in two steps. First I used a hand filer to remove the big chunks of material and with the help of Joe, the Machine Shop Manager, the edges were finished using a grinder. After it the piece looked like this:

The surface was not uniform and had some rust and stains. So I decided to sandblast the piece. It gave Texas the nice and metallic look I was looking for:

Since I wanted my piece to look like metal, I decide not to paint it so my last step was applying a protective coat to prevent rust on the metal, resulting in the final piece looking like this (that is pretty much what we had before the coating):

Looking closely one can see some defects on the borders, it happened because the coating applied on the border dripped to the other side creating some chunks on the borders and sticking to the cardboard beneath the piece. Since I could not find a way to avoid these chunks while spraying or to remove them and they are very small defects I decided to leave them and declared my part finished.

With this assignment I could learn a lot about plasma cutting, the limitations and advantages of the process, and post processing, what operations you can do on your piece to best fit your needs and make it look better. I could learn how to operate new tools and equipment in the OEDK as well, such as the filers, the plasma cutter and the sandblaster. In addition, I learned that post processing depends on the intent for the part, how do you want it to look like, how smooth the edges and surfaces have to be for the application you seek, if it needs corrosion protection and all factors related to the part performance in duty.

In addition, I’m happy with how my Texas looks, with a nice surface finish and keeping the metallic look I wanted.

Thanks for the attention! See you guys on the next assignment.