Pretzel Slime

This project was created during “ENGI 210: Prototyping and Fabrication”, a course I took Spring 2019. See original posts.

This week, our project was to create a “diamond shaped” art piece using an aluminum/steel sheet of metal; the purpose of this piece was to explore the plasma cutting tool, while also practicing post-processing techniques learned in class.

I wanted to create an object inspired by my fascination with biology and organic structures. After some research for inspiration, I came across pictures of Hemitrichia serpula, also known Pretzel Slime Mold.

(Photo credit: Jessica Rosenkrantz‏)

To begin my project I decided to trace the shapes of the slime mold in Illustrator. This method was a quick and easy way to develop a pattern that the plasma cutter could later cut out of metal. After I aligned my shape’s outlines to the diamond form, however, it didn’t look as cool as I expected.

I decided to experiment adding a second copy of the shape to create a more symmetric profile. I really enjoyed how intricate this new object looked, but once I loaded it onto the plasma cutter the piece totally failed to print!

It turned out that the holes were way too small and close together, and the plasma cutter cut right through the intersections. I needed to find a better design and solution to this problem soon. To simplify my vector path, I traced out my shape on a piece of paper, then re-drew the inside area.

Once I got my new drawing prepared, I transferred the lines on to illustrator and began plasma cutting two copies.

For my material thickness I chose to cut the shape at 100 in/min. I took a wire brush to the back of the object to remove any dross left on the inner edges of the shape. This left the back of the pieces with a bumpy texture which I really enjoyed – I decided to leave this surface untouched.

My next step was to create rounded interior edges to mimic the slime molds round structure. I did this by taking needle files to the metal along the interior. Instead of filing evenly along each hole, I decided to create better depth by alternating my filing patterns. This step ended up taking up a majority of my time for this project, spending about 4 hours filing both object (though it was a relaxing opportunity to watched Hulu/Netflix).

Once I was done filing the pieces, I was left with a few extra scratches on the surface; I decided to use the sandblaster on the front faces to remove the major flaws. After that I followed up with by buffering both shapes and finishing off with an aluminum polish for protection.

Overall I was really happy with how these shapes turned out. I wish I was a bit more careful with the needle files, leaving a few scratches still visible, but I was able to capture the organic form of pretzel mold through the intricate design & finishing techniques.

Tools I used?

  • Adobe Illustrator
  • Plasma cutter
  • Needle Files
  • Sandblaster
  • Wire brush & Buffering wheel
  • Safety gear; face shield, leather work gloves, goggles

Cost?

Time-cost played a huge factor in creating this object. I spent about 2-hours in the initial design phase & prototyping (failed plasma cutting attempts) before I was able to get my pieces cut. After that I spent an additional 4-hours filing, and 1-hour finishing (sandblast, buffer, polish). In total about 6-7 hours were spent in finishing this project, although for the next time I’d be more efficient in the plasma cutting stage.

In materials, a 1 ft square sheet of 1/8 inch aluminum would cost about $8.50; and a tub of Mothers Mag & Aluminum polish would cost $5. Because I was able to get these materials free from the OEDK, I didn’t have to spend out of pocket.

Machine & tools would have played a huge operating cost doing this on my own. At the OEDK I was able to easily access a plasma cutter, sandblaster, wire brush & buffer – most of which aren’t feasible to own at home. I’d add about $50 of cost to access a similar machine shop at TXRX.


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