If you live in LA, you probably are familiar with huge freeway interchanges. It’s an impressive network of forming a big knot that somehow channels various streams in all the possible ways. It has huge curves sweeping above and below the main wide arteries. Anyway, they are cool. My favorite is where the 110 and 105 interchange and I’ve been mulling over making a cement casting of it for a while now. It starts with grabbing 3D data from the interwebs and turning it into a functional model.
Once the data is prepped, I prepare it for 3D printing. I want the final piece to be 26 inches wide which is wider than any printer I could get my hands on so I break it up in tiles and run some tests.
Next step is to figure out the process of making the mold. There two options but the first step for each is the same: glue the tiles back together (there will be 16 of them) and use bondo, sand paper to smooth out all the irregularities, and spray paint some urethane to smooth over the result. The question is: should I make the urethane mold directly from the positive 3D prints, or should I create a positive plaster intermediate I can tweak and further polish, and make a mold out of that? If I go with the plaster, I worry that the brittle nature of the plaster and the rigidity of PLA filament will cause the small details to break as I release the plaster image from the 3D print. If I pour the mold directly on the 3D print, I worry that the tell tale 3D print lines will be captured by the mold and that I will not have had the chance to polish it with the control a plaster intermediate would give.
So, next step is to test both approaches on my two test prints, and also test printing a tile with PETG filament which I hear is more flexible. If you have any recommendations, I’m all ears…