Welding And Casting ABS

Anybody who has a 3D printer always has a ton of useless plastic lying around. Some of that plastic may be from useless baubles, but most of it is in bad prints, short bits of filament, and general scraps. [Luke] found an interesting way to put those ABS scraps to use, and ended up turning trash into valuable plastic parts.

Commonly sold as nail polish remover, acetone will turn anything made out of ABS into a puddle of plastic. [Luke] makes glue using the same process – he fills a small container half full of acetone and half with small bits of ABS. After a day or so, he has a nice thin glue that dries into solid ABS. [Luke] used this to create a 400mm long piece of extruded t-slot. We don’t know if it would be suitable to build a child RepRap from, but it would sure be an interesting experiment.

[Luke] also did a little bit of casting with his ABS glue. With a thicker solution of ABS and Acetone, he managed to make this ‘thing’. The entire process is explained over at Thingiverse, We can’t wait to see what can be done with this stuff.

31 thoughts on “Welding And Casting ABS

  1. This could certainly come in handy for fixing my kids’ toys. Nothing I’ve tried seems to work up to this point, including an attempt to weld it with a low-temperature soldering iron (couldn’t get the heat to penetrate deep enough, so it just welded a thin layer at the surface).

    I’ll have to give this a try…

    1. In case you didn’t know, in industry they weld plastics with ultrasonics, it’s always a annoying thing to deal with as amateur to weld the stuff I find and then I saw on discovery’s ‘how stuff is made’ mentioned that they welded some plastic using ultrasonics, which didn’t help me of course :/ but oh well.

      At the risk of coming off as some wikipedia spokesperson a link:

  2. Generally polish remover doesn’t contain too much acetone as it extracts water from almost anything and nails are breaking more easily. You can buy acetone in shops with paints, but it may be sometimes hard to obtain as acetone is often used to make crystal meth.

  3. I’ve been doing this for a while with parts from my MakerBot. As pointed out, the bond will actually be stronger than the part itself. It’s also great for “sealing” any imperfections that might otherwise fray or crack.

    The nice thing is that clean up is efficient. After painting on the glue, I rinse the brush in fresh acetone and dump that back into the ABS solution. No waste!

    I usually thin my glue down to the consistency of a recently mixed epoxy or slightly thinner. That seems to make it easy to work with. The thing to remember, however, is that this stuff will start to thicken quickly once you spread it. If you’re sealing or painting over imperfections, you’ll need to thin it down more or work quickly. Otherwise, you’ll start smearing clumps.

    1. “As pointed out, the bond will actually be stronger than the part itself.”

      I have different experiences. I made a new front panel for my computer by gluing 3 mm ABS sheet. I used it for a number of years, and when I finally disposed of it I took it apart by snapping it into pieces, and I found that it invariably broke at the seams.

      The glue leaves tiny voids in between. Here’s a picture: http://koti.mbnet.fi/jeti/IMG_3896.jpg

      1. I’m not sure exactly what you’ve used there, but this is the chemical equivalent of welding the plastic pieces together, melting the plastic so that it flows together again in a stronger bond than what simply gluing the surfaces together with an external adhesive does.

      2. It’s not the same thing as welding, which is melting the plastic by heat.

        Acetone is dissolving the plastic. It gets in between the polymer strands and untangles them so they float freely, and when it’s gone they settle back down into a solid with a different structure more like a salt crystal, and it tends to be harder and more brittle than the original plastic because you’re re-arranging the polymer strands in a different way than you’d do by welding with heat. There’s also a transition from two different polymer structures at the seam where the glue meets the bulk plastic, which becomes a weak point.

        The second problem is that the solvent increases the volume of the solution, so the glue shrinks a lot as it dries. It dries fast at the outer edges and forms a seal, so the inside parts of the seam experience a vacuum as the acetone diffuses out, and that leaves bubbles in the glue.

        So the joint between the two sheets becomes filled with tiny voids that compromize its strenght. In the picture I had glued ABS sheets together with the same plastic dissolved in acetone, and after some years I tore the seam apart, and that’s what it looks like in between.
        Full of little holes.

      3. There’s one great application for this stuff however: a thin solution of ABS in acetone works great for laminating paper into a composite, much like how you’d work with glass fiber.

        There’s also other tricks you can do. Make a very thick solution and dump it in a bowl of water. The acetone dissolves in the water, so it strips the acetone off quickly. Simply knead the blob under the water and you get something that resembles soft rubber that sticks to itself, that will harden completely solid over a week or two and tends to form a surface that looks like leather.

        It can be pressed into molds but it will take a long time to dry, but if you heat it, it will actually expand and fill a cavity with plastic foam.

  4. MEK (methyl ethyl ketone aka butanone) does a better job on ABS than Acetone. Had a plastics shop next to me years ago I did business with. The guy would mix up ABS shavings and MEK in a bottle and use it as gap-filling ABS glue. Worked brilliantly. MEK can be had cheap at your local hardware store.

    Macona, “ABS glue” is basically clear ABS disolved in MEK. Definitely more economical to get that if you only need a little.

  5. Pure 100% Acetone is available in most mega-mart beauty aisles, right next to the other nail polish removers. Seems to me it is about $1-2 for a bottle. Agreed, though, that MEK, or a mixture of MEK (90-ish%) and acetone (10-ish%) works better than acetone alone. This mix of solvents will also work well with PVC, acrylic, polycarbonate, and polystyrene plastics. Oh, the things you learn from building Nerf guns.

      1. One tidbit from that article:

        As butanone (MEK) dissolves polystyrene, it is sold as “polystyrene cement” for use in connecting together parts of scale model kits. Though often considered an adhesive, it is actually functioning as a welding agent in this context.

  6. quick question to the pros:

    if i had a couple of ABS scraps could i recycle them by making new filaments by using this tech?

    I imagine one could use extruder to draw a filament. I guess also that it depends on how fast one would get the Aceton out the solution.
    So if one would use vacuum-chamber and a slightly heated extruder (just a theory, i dindt do any math on this) you could get the aceton to boil out fast enough to get a useable filament. If you can capture and cool down the aceton after that yo could create a continuous process.

    1. In my experience, casting anything with ABS and acetone leaves a lot of voids because the material shrinks when the bulk of the acetone evaporates. Your filaments would be full of bubbles of various sizes.

    2. You may be best off looking up how ABS is currently recycled and just replicating that.

      Assuming its something that scales down well, the method will have all the kinks worked out of it.

  7. Just an FYI that i diente ser in the comments. For the best bonds its always a g[d idea to clamp parts togethet. This will minimize any issues of tiny air bubbles in the joints. Though in my experience Ana bonds so well with MEK or MEK and mixture that this is a moot point. I’ve made many sealed leadacid battery boxes with abs, suspended below a bike frame and I’ve never had a joint failure. These batteries are very heavy and the peak live load forces have to be very high when riding

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.