Experimenting With Acetone

After seeing many gloriously polished ABS prints which had used the acetone vapour method for smoothing and hearing of the legendary adhesion achievable on a heated bed with a fine coating of ABS juice, I decided to buy some acetone and see for myself whether it might help me in some way. People had said it could be had from pharmacies, hardware stores or even from the supermarket in little bottles of nail polish remover(though apparently a lot of nail polish removers are now acetone free), so I went to the hardware store where they sell a litre of it for $10 (I don't know if this is good value or not, but it sure won't break the bank anyway).

First up I tried the vapour smoothing method on an ABS model I had lying around - a squirrel with plenty of curved surfaces for the acetone to smooth and polish up. The first thing I noticed was how fast this stuff evaporates; I spilt a bit and it evaporated in seconds, the evaporation also makes it very cold when you get some on your hands. ...and on a note of safety: acetone is flammable and though not a proven carcinogen, it's not something you really want to breathe the vapour of or have on your skin for a long time and especially not in your eyes so be careful. Take care where and what you store it in as well: some types of plastic containers may dissolve and acetone in a hot place = vapour = pressure/expansion. This was the setup I used:

The squirrel before the acetone vapour treatment

A platform I quickly put together to suspend the model above the acetone. It is made from some solid-core copper wire twisted together then bent into shape, there is then a piece of aluminium foil put over the loop at the end for the model to sit on. At the top is a hook which goes over the rim of the jar. This platform is not very effective because it doesn't sit far enough down in the jar to allow the model to get the most of the acetone vapour which is most concentrated lower down. Also, it's not very stable and has a tendency to push the model into the side of the jar under gravity.

The jar sitting in some boiling water with the squirrel suspended, about 2mL of acetone in the bottom of the jar and the lid just sitting on top of the platform's hook since it doesn't allow it to screw down - good for stopping pressure build-up I guess.

The final result of the squirrel sitting in the jar for about one or two minutes. The plastic is definitely a lot shinier, especially lower down, and there are no layers distinguishable lower down. I took it out at this point because the surface at the bottom was starting to get very gooey and liquid-like to the touch, whereas it did not appear that much was happening with the higher layers. The main disappointment is that it has not been uniformly smoothed, with most of the smoothing at the bottom, I think this is because the vapour is most dense in the bottom of the jar and the platform the model was on was already too high up in the jar. When the model first came out of the jar its surface was very soft to the point of being gummy, after about ten minutes, it was hard enough to gently pick up but I easily left a deep gash with a fingernail, in the end it took a couple days for it to fully harden to how it was before the treatment.

After the vapour treatment experiment I decided to make some ABS juice with which to coat the bed to get very nice adhesion (or so people say). ABS juice is just a bit of ABS dissolved in acetone so the liquid mixture can be put on a paper towel and spread over the build platform, with the acetone almost immediately evaporating, leaving a very thin, even coating of ABS. You don't need to dissolve much ABS in acetone for this to work, I put the little ABS pieces seen in the photo above into that half-full tube in the photo. When coating the bed you will notice a quickly evaporating streak of acetone behind the wad of paper towel, I keep wiping the towel over the glass until I very barely see a bit of cloudiness on the glass. I don't seem to need much for it to adhere very well and I don't want parts sticking like crazy and pulling chunks off the glass when the bed is cold. How concentrated and how much ABS juice to apply appears to vary by supplier of filament and bed surface according to people's experiences I have read in the RepRap forums

The colour of the acetone after the ABS dissolved in it.

The bed appears to need to be coated again where the footprint of the part was after each print as each print takes the coating with it. An alternative to re-coating after every print is to "redistribute" the ABS residue from unused parts of the bed by wiping the bed with acetone, though you will still have to apply more ABS juice every few prints to "top up" the bed with ABS residue as "redistribution" takes a lot of the residue away in the process. Also, nophead claims that ABS residue can get baked on after a while of sitting round not being redistributed or printed on, this baked on residue becomes discoloured and is allegedly highly adhesive and thus tends to pull shards of glass off with the part. So even if there are some areas round the edges of your bed which barely get used it may still be worth redistributing and re-coating along with the rest of the bed.

I think I am going to permanently move from using sugared water on the bed to using ABS juice. This is because it saves time and has better adhesion, though it is much more expensive than some sugar and water. With ABS juice I don't have to create a new mixture every week due to stuff growing in it as it sits around, as with sugared water. The coating on the bed can also be redistributed instead of cleaned and re-coated which takes less time. Also I don't need to wait around for the bed to get to 80 degrees C before I can even coat it(this takes about ten minutes): ABS juice is just applied at room temperature because the acetone evaporates so quickly, so now when I click print I can walk away. With sugar water I have to be at the printer on the first layer because when plastic first comes out in inconsistent sputters during those priming loops, it has a tendency not to stick and instead clumps to the extruder. The blobs then begin pulling up good outlines when the filament flow is fully primed, the solution is to wait with a bamboo kebab skewer and push the blobs off the moving extruder and into the bed. Because of this I have to wait the full twenty or so minutes it takes the printer to warm up, stabilise temperatures and begin its first layer after I hit "print". With ABS juice these blobs never form in the first place because even the inconsistent, sputtering priming extrusion loops stick to the bed. On top of this, I save time after the print is done since I don't need "brims" around the base of the part to stop the odd corner lifting a bit since ABS juice has stellar adhesion, thus I don't waste time removing the brim afterwards. As always, parts just detach by themselves when the bed is cooled.

If you use ABS and can find some acetone I recommend giving this a go, especially if kapton of PET are not your thing or too expensive to get hold of.