Convert plastic bottles into 3D printer filament

35 points by svarrall 5 months ago | 14 comments
  • RobGR 5 months ago
    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.

    • starkparker 5 months ago
      > There are a series of youtube videos by a Russian guy building a log cabin in the woods, and he utilizes those strips extensively

      Advoko? https://www.youtube.com/watch?v=GSBh77bjz_Q

      • RobGR 5 months ago
        Yes, that is who I was thinking of.
        • RobGR 5 months ago
          I think he switched to this tool and wire https://www.youtube.com/watch?v=mRc7ZDRcgrQ , but he made the PET strip material popular in the bushcraft community, and from there I think it crossed over to the 3D Printing / Maker community and got picked up for making filament.
      • schiffern 5 months ago

          >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.
        As I understand it, most PET bottles are recycled by being spun into polyester.

        So where are all our old plastic bottles? Mostly, we're wearing them.

        • avidiax 5 months ago
          Yeah, but then we've moved to fast fashion, and we assuage our guilt by "donating" or "recycling" clothing. Of course, nobody that "donates" or "recycles" clothes has ever worn any such clothing themselves.

          So sure, we get one more use out of that clothing, and then it gets put in a landfill or "donated" to west African countries that receive a year's supply of clothing every week.

          https://www.bbc.com/news/av/world-africa-58836618

      • pseudonymcoward 5 months ago
        Maybe I'm an idiot, but I was really struggling to understand how this worked from the website, which seems to have no photos or video of it actually operating.

        I searched youtube and found a youtube short of it being used.

        First you have to use another small machine to slice up a plastic bottle into a spool of roughly formed plastic spaghetti. Then you feed it through the nozzle on this machine to draw it into a properly formed filament.

        Having to slice up every plastic bottle you want to run through it by hand seems like a cost to using it in any kind of bulk (I originally was trying to work out if it melted them down which would alleviate that).

      • bdcravens 5 months ago
        There are a variety of open source projects to do this.

        One thing to consider is that PET isn't the same as PETG, and may require changes when printing, and possibly additional ventilation

        https://all3dp.com/2/pet-vs-petg-differences-simply-explaine...

        • stavros 5 months ago
          This is a really cool project, but obviously don't expect the same quality of filament as a big company. The width will vary across the length, leading to inconsistencies in the final part.
          • tocs3 5 months ago
            Looks interesting. Just bought a tiny 3D printer and had to by my first spools of filament after running out of the sample spool that cam with the printer. I do not think I will go this way (I am not printing much) but it is nice to see this sort of thing.

            Also from the link (I just thought it was a little funny and answered a question I had)

            > "Do all plastic bottles work?

            Yes, as long as the bottle is made of PET. But the bigger the bottle the more filament can be made per bottle! Plus don’t forget, any colour of bottle will work!

            • kazinator 5 months ago
              Problem is, I paid a refundable deposit on the bottles, as an incentive for returning them.

              If I lose 10 cents by turning a 500 ml bottle into filament, will I get at least 10 cents worth of filament out of it?

              • imtringued 5 months ago
                You can probably get 25 cents worth of filament out of a plastic bottle. Most of your savings will come from not having to pay taxes.