Smoothing 3D prints with acetone and without patent violations

Austin Wilson and Neil Underwood from the North Carolina makerspace Fablocker invented a great, simple process for smoothing out 3D prints using evaporated nail-polish remover in a large jar. The process produces a beautiful finish and sidesteps a bunch of dumb patents for polishing 3D printing output. They're still experimenting with the details, and the fact that the first experiments turned out such great looking pieces is cause for excitement about where this will go when it's fully refined.

ABS-based printed parts are placed in the jar with the acetone and heated to 90 degrees Celsius on the hot plate. Acetone has a low evaporation point, but is heavier than air so the process creates a small cloud around the model which melts the surface, slowly smoothing it to a mirror finish. After a couple hours, the parts solidify, can be removed, and be displayed with pride.

...Since their initial success the duo has been experimenting with the process by controlling temperature ranges and exposure times, but there are still many tests to be conducted. One area in need of more research is measuring how the process impacts the physical properties of the parts. “It doesn’t really seem to change the shape of objects or alter the dimensions, but we haven’t had time to do test cubes and measure them with calipers,” says Wilson. “If anything the smoothing out process might make things work better. People have tried to use 3-D printed models as bushings and axels before, but they never work because they’re too rough.”

Slick Trick Adds Much-Needed Shine to 3-D Printed Parts [Joseph Flaherty/Wired]



  1. I hope they patent the process, if only to make sure no one else patents it and expects royalties from the use of the method. Very cool and clever on their part!

    1. By publishing as they have it is now prior art and not patentable by others. It would be especially helpful if they mentioned a few variations that they find obvious to try next. Such statements would make it difficult to patent the variations because they are explicitly “obvious to one skilled in the art.”

    1. It’s always worth looking up the Material Safety Data Sheet (MSDS) and understanding it. For acetone:

      Here’s the relevant portion for acetone fumes:

      VAPOR (LC50): Acute: 50100 mg/m 8 hours [Rat]. 44000 mg/m 4 hours [Mouse].

      These are the vapor levels and exposure times that are likely to cause acute harm (like death) in humans, as well as rats and mice. There is more about potential chronic health effects.

      Low, and occasional higher, vapor levels are tolerated in many manufacturing and nail polish environments.

      1. Also: The flash point of acetone is very low, so if you’re intentionally vaporizing it, be careful about sparks or static electricity

        1. This was my snap reaction. It’s quite possible to do this safely, but I really don’t want some less careful, less informed hobbyist – possibly in my apartment building – vaporizing acetone in a closed space, with a convenient heat source and everything.

        2. But then if goons from a rival 3D print gang bust into your lab and demand the recipe for your cook, you can just throw that hot acetone in their faces and run off in your underpants.

    2. Pure acetone is toxic to living cells, although exposure to skin (or finger nails) is not usually a cause for concern if washed off.

      Vaporized acetone would be extremely harmful if it enters the lungs.  In the past I’ve put on a gas mask before being exposed to it (usually when cleaning air brushes).

      1. Well, in moderate doses, it’s perfectly harmless – seeing as how your body manufactures acetone…

        1.  Perfectly harmless , Eh?  Take a small cup of acetone, (NO! not the plastic one!) and dissolve some chocolate in it.  Now stick a finger in it for a little while.  Taste anything?

          1. Well, my body produces poo, too, but that doesn’t mean that I want to aerosolize it.

          2. Technically, the gut in your intestine produces the poo.

            My apologies. I should have been clearer earlier. Your body makes and USES acetone.

            Yes, I was surprised too.

  2. That’s kind of like antialiasing something by blurring it. I have an idea. I wonder if it’s a new idea or not. Has anyone 3D printed in material that shrinks on heating, like a toilet bowl or a tiki mug does during its manufacturing process? Then the steps would be a lot smaller after the object shrinks, sort of like antialiasing jaggy b+w text by re-sampling while reducing it in size.

    Although it’s probably not feasible. You’d probably need a 2:1 scale change at minimum before the advantages would start to be worth it. 4:1 even better, and even less likely. You’d need to be able to print something like a 3D Shrinky-Dink

    1. When the end heats to extrude the plastic, would that make it a lot smaller from the get go?  Then as it cools it enlarges?

      I’m confused.

      1. I’m saying make something 20 inches tall with 1 mm steps in the surface with the intention of shrinking it to a final size of 2 inches tall and the steps in the surface will be 0.1 mm. The problem is there is not really a process for massively and accurately shrinking things, so it’s really not feasible — although certain ceramic things, like toilet seats, are made oversized because they shrink maybe 20% when fired.

    2. abs contracts on cooling- just a few % though. Anything with a really big thermal expansion coefficient would probably wreak havoc with precision unless you had excellent temperature control during deposition

  3. Interesting approach but this is not a very safe method in current form. Solvents should never be heated on a hot plate and certainly not in a sealed container. In addition the container in the image does not look like it is heat resistant glass. Fortunately acetone vapor is not easy to ignite but but this is still quite risky especially if there are any open flames in the workspace.

    1.  It doesn’t look like they sealed the container.  That’s why it was important that the acetone fumes are heavier than air – they push the air out of the unsealed container but enough to fill the container remains behind since it won’t float up out of it.

      You do still need to be careful heating a solvent, and please don’t inhale it.

  4. Still might not be the best for bearing/bushing and the like. Sure, you get a smooth surface, but this process will still play hell with your tolerances.

    1.  Isn’t this really a hardware version of a low-pass filter? Which reduces mechanical “noise” at the cost of precision. If over-used, the result would be just a blob.

  5. Is it just me, or is the end product just a little plastic animal? I mean, 3d printing is cool and all, but I haven’t noticed a lack of cheap plastic crap in the world.

    1. Yes, its a demonstration.

      You can also do things like 3D print gear assemblies in one step that would be unassemblable if made in multiple pieces.

      And plastic crap is cheap because its mass produced. If you happen to be an engineer, making that first prototype of a part through non-3d-printing means is quite expensive. And custom goods are a lot costlier than mass produced kinds – but not with a 3d printer.

      1. This technique wouldn’t be useful for assemblies printed all in one, though– the parts would stick together.
        What it would be extremely useful for is when you want to cast from 3D prints.  If this technique can work as well as the pictures suggest, then it opens up a whole range of possibilities.  I’d love to try casting lenses at home, for example…

  6. This technique has been patented and commercialized by Stratasys. I suspect the patent is weak, because it’s really just a variant of vapor-phase degreasing… which is a century old.

  7. Very impressive results! But I do have grave reservations about the home-based, DIY person working with heat and acetone.

    Way too much could go wrong. It sounds like a prescription for disaster.

  8. Vapor deburring isn’t new, but it is neat. I know of a company in Tennessee that does it to remove machining marks on optically clear plastic. They buy clear blocks of plastic, then mill them to the shapes they want, then vapor debur them so they can use them as sight glasses. Neat stuff!

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