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ExtremeDullard @lemmy.sdf.org

Cheap filament splicing method

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:

27 comments

  • I'm wondering if there's some obvious reason I'm missing why you couldn't make a filament splicer by just taking a slug of aluminum billet or copper, drilling a 1.75mm hole through it, and sawing it in half bisecting the hole with, say, a jeweler's saw so you have a minimal kerf.

    Assemble the halves, stick your two pieces of filament in, cook it, let it cool, split the halves, nirvana achieved. No waste, no consumables.

    Like... Not a single commercial splicer gizmo works that way. Why?

    • I’m wondering if there’s some obvious reason I’m missing why you couldn’t make a filament splicer by just taking a slug of aluminum billet or copper, drilling a 1.75mm hole through it, and sawing it in half bisecting the hole with, say, a jeweler’s saw so you have a minimal kerf.

      I'll tell you because I tried making one:

      • You need the hole to be at least 30 mm or 40 mm long so that the two filaments are held in place where they're not melted. Good luck drilling a 1.8 mm hole that deep! Not impossible, but not easy, as any machinist can tell you.
      • You can't split the block in two through the hole because you always lose material where you saw off. Even EDM machining will lose you 0.2 mm, so your reassembled block would have an oval hole that's too small. To create two halves that reassemble and create a correct hole, you need to make two identical blocks and mill them to exactly the center plane, which considering the diameter and tolerances of the hole, really isn't easy to position right. Again, doable but not easy.
      • The block will act as a massive heat-sink. Even if you leave the center part thin so the heat has the best chance to reach the splice, it will still mostly go into heating the masses of metal around it.

      TL;DR: it's not a trivial bit of machining. And remember: my goal here was to make this ultra-cheap and lazy 🙂

      • So, hypothetically, could you use a ball end mill with a 1.75mm diameter? Then mill the channel across two halves?

        Basically, something like a halved heater block. Put a cartridge heater on one side, thermistor on the other, take it up to a melt temp and shut off. (Maybe add some cooling fins beyond the intended melt zone?)

        Also, have regrets because this is more expensive than the boden tube method.

  • Neat. Can you eli10 me on reasons for doing this? Is it primarily if you don't want to have to attend to a pause for a color change?

    • This is to use up the leftovers from almost empty spools of filament, most realistically. Figuring out exactly where in the filament's length to put the splice for a controlled color change would be incredibly difficult and involve a lot of variables that'd be tough to account for (like the volume of your melt chamber, amount of nozzle prime, retraction, etc.) so it would only be a benefit if you didn't care where the color change happened.

    • 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 🙂
27 comments