Saturday, 5 January 2013

Smoothing

In an attempt to improve the finish of my models I have started experimenting with acetone vapour smoothing.

Stratasys offer a smoothing station for around $40,000 but I wanted something a little cheaper....

There are a few others on the net getting very good results with putting models in a cheap deep fryer or cooker and heating a small amount of acetone for a short period to vaporise the acetone and smooth the model.

Another option is to place the model in a sealed container with some acetone, and leave for a few hours. This method is the cheapest, but also the slowest.

A few things about acetone vapour. Firstly its rather toxic, so breathing it in is definitely not recommended. Its also explosive and evaporates at around 50C. And lastly it is around twice as heavy as air. This last point is somewhat of an issue with the passive smoothing method, as a part will smooth from the bottom up and so won't be even. On smaller models this doesn't really cause a problem, but when dealing with taller models I notice the bottom of the part looses more detail and can sometimes cause the part to warp or completely fall over, whilst layers are still visible at the top.

Ideally the vapour needs to be circulated around the part so as to get a good even covering. Something I'll work on in the future.

Another thing I noticed is that the part continues to smooth even after it has been removed from the container. I was quite happy with the result I had on a small figurine,so removed it from the container and left it on a bench to dry over night. In the morning I was shocked to find the part was far smoother than when I left it, and had lost much of the detail it showed the night before.

Now when a part is removed I put it into the freezer to halt any further smoothing.

Parts can vary on how long they need to stay in the vapour. depending on the size of the object and also the ABS. The dragon below for instance was left in for about 12 hours. Its relatively "soft" ABS, but the part was quite large. The terracotta warrior on the other hand was left in for just over 2 hours.


 Here you can clearly see the layers.

 This is the dragon after the smoothing vapour bath! The surface is as smooth as glass.
You can still just make out some layers, but these seem to be "underneath" and cannot be felt.

Another before ...
 And after











6 comments:

  1. Awesome results !

    (Definitely tweeting it!)

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    1. Thanks Dizingof!

      Still printing those coasters btw, but I had a delivery of nylon arrive so have been experimenting with that. I'll get back to the coasters soon. But they take 1.5hours each.....

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  2. Excellent! I was wondering if you might tell us how big the parts were, how much acetone you were using, the container you put it in and the ambient temp.

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    1. Hi John,

      Thanks.

      The parts vary, but the dragon is 123mm (4.8") high and the sofos 113mm (4.4").

      I used exactly a "dash" of acetone in the bottom of the container. Sorry can't be more specific. I don't think it makes a great deal of difference, as long as there is some there.

      The container is just a plastic lettuce container ( the container is plastic, not the lettuce!!) It needs to have a 3 or a 5 on the bottom to be acetone safe.

      Temperature was about 25 C (77F). Oddly enough higher temps don't seem to improve the process. I left the container out in the sun and I think the warm air creates a more distinct separation between the vapour and air. the part melted at the bottom but the top was untouched.

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  3. The reason i find this process exciting, aside from aesthetics, is using Acetone vapor smoothing on my "3D printing ABS mold for Metal casting" tutorial:

    http://www.thingiverse.com/thing:33450

    With a free software you create a positive mold of your design, 3d print it with ABS, vapor-smooth it then use your kitchen oven to melt a low-cost low-melting-point metal called Bismuth to pour it into the mold, let it cool and finally dump it in a jar with Acetone to peel off the ABS cover.. - You now left with a 3d printed metal design! way way cheaper than the $8 per cubic CM offered by 3d printing services..

    That sound like a new project to tinker with? ;)


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    1. Aha! Very cool. I'll definitely look into this. Thanks Dizingof.

      Seems hard to find Bismuth in Australia, although apparently we have large deposits of it here, I can't find a store selling it. Might have to get out the shovel!! 8-(

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