Here’s a method I’ve developed to splice filaments almost to perfection without any tools. It’s basically the Teflon tube method for cheapskates who don’t want to buy Teflon tubing 🙂

First of all, prepare a 2" x 2" (50mm x 50mm) -ish piece of white paper and a straighten a piece of filament that will serve as a mandrel:

Roll up the paper into a tube around the piece of straightened filament as tight as you can. The hard bit is to start rolling: the paper needs to be really snug against the filament to start with.

Once it’s started right, it’s easy. Roll it up all the way nice and flat. The bit of filament inside should fit inside the tube with quite a lot of friction if you did it right:

You can also wet it a few times with your tongue and it will stay in one piece without holding it. Ex-smoker’s habits die hard 🙂

Cut the ends of the filaments to splice together with a sharp bevel:

Carefully thread the ends into the paper tube so they meet halfway:

They should go in with some force but they should slide smoothly. If you feel any roughness, you’ve snagged the paper inside and it won’t work, so you should start over.

Heat up the center of the tube at 250C to 260C while ramming the filaments into each other firmly, but not so firmly as to collapse the paper tube, until you feel them “go” and melt into one another:

I use a SMD rework station because you can apply heat as much as you want and the paper only browns a bit, even if you overdo it grossly. It takes about 30 seconds for the heat to diffuse through the paper and for the filaments to melt fully. It’s doable with a lighter too while pushing the filaments together with one hand, but it’s less convenient of course.

Then unwrap the paper: some paper should stay stuck to the splice:

Clean up the splice by running a sharp knife along the splice all around. It’s pretty quick, the paper isn’t terminally fused to the filament:

Voila: perfect splice!

And here, seen under a microscope:

  • @[email protected]OPEnglish
    8•22 hours ago

    Four reasons:

    • I have a million “almost empty” rolls of filament that I want to take the time and reclaim at some point. But I haven’t seen a splicer that I really want to order, and the throwaway tube method (you know, pieces of PTFE tubing that you use once and then cut and discard) seem really wasteful and terrible for the environment.

    • I want to assemble a filament composed of teeny tiny bits of filaments of different colors - like half-inch bits - to create a sort of “jawbreaker candy” filament. You know, those candy balls with a million layers of different flavors that successively melt in your mouth. I really want to see what the surface this would print into looks like.

      The problem is, you can’t really find a splicer that splices bits of filament that small. It’s a solution to that problem I’m really after. The paper thing is just my latest attempt at making this somewhat doable without losing my mind - because for the print I want to do, I have to assemble 200 of those tiny bits.

      I tried to do it once: I hand-spliced all the pieces and cold-forged the splices with a special pair of pliers I made. It’s completely madderning, and it didn’t do a good enough job: the filament went through 3 segments before jamming inside the extruder hard. It took me half an hour to clear the jam.

      It failed but if you want to see what that particular attempt looked like, here’s the filament and the special pliers I made, if you want to see what I’m trying to achieve at scale without going mad:

      The paper thing doesn’t make this particular project any easier, but it does make casual, “normal” splicing better at no cost. So I figured I’d share.

    • I like to come up with my own solutions rather than buy ready-made.

    • I’m cheap 🙂

    • @[email protected]English
      3•20 hours ago

      I want to assemble a filament composed of teeny tiny bits of filaments of different colors - like half-inch bits - to create a sort of “jawbreaker candy” filament.

      Props to you for going through the effort, but damn does that sound like a huge PITA.

      I wonder if you could achieve the same by using a mold with scrap bits of filament in the oven or something.

      • @[email protected]OPEnglish
        3•20 hours ago

        My next step will be to turn a 1.4 mm diameter extruder with some length of rigid tubing with a flared end, heat it up to melting temperature and force-feed it the bits - essentially extruding brand new, slightly thinner filament. But first I need to test if the extruder physically accepts a smaller diameter. The slicer software does have a setting for the filament diameter though, so I’m hoping the wildcat filament will feed through.