| I have followed various open source projects to produce filament this way for a few years, starting from a facebook group. It is called "pultrusion". A key property of PET plastic is that it is not infinitely re-meltable, it gets more brittle each time. If you melt bottles to form filament, then melt it again when printing, those two re-melts are too much. But, you can heat it enough to soften it without truly melting it -- so it does not loose strength -- and pull it through a heated nozzle, that kind of wraps the little strip around into a tube, sometimes with a small hollow center like a straw. There is then one full melt left in the plastic's life to allow a 3D printing. You might have to adjust for the filament being hollow and extrude a bit more. You also get a filament with a shorter length, just the plastic from one bottle, because joining the filaments is finicky and no one seems to have come up with a reliable way yet. In spite of all this, it's really appealing because getting one more human use out of the vast volume of PET bottles that are thrown away seems really useful. Note, that the strips that you cut the bottles into, are useful by themselves. There are a series of youtube videos by a Russian guy building a log cabin in the woods, and he utilizes those strips extensively -- if you use them to tie things together, you can pour hot water on them or heat them with a flame and they will shrink and stick to themselves, making a really strong joint. |
Advoko? https://www.youtube.com/watch?v=GSBh77bjz_Q