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Topic: Acetone Vapor Bath

I did a vapor bath test with a failed Pony print.  This was nothing more than 1/4" of acetone in the bottom of a paint can with the lid on.  I turned a metal cup upside down and set the pony legs on it, and left it for about 4 hours.  No heat or anything, just the room temperature evaporation of the acetone in a closed metal container. 

Safety wise, I don't see this as being any different than storing acetone in the metal container it came in, this one is simply big enough to hold a model too.

I'm pretty excited about the results, I just need to find a way to carefully lift it out by the cup without needing to touch the model until it has dried.  There's a Yoda marinating in there now, we'll see how it looks in about 3 hours.  Hopefully the timing will be right and it won't be another Yoda in the style of Salvadore Dali.

http://solidoodletips.files.wordpress.com/2012/09/photo-19.jpg

http://solidoodletips.files.wordpress.com/2012/09/photo-17.jpg

http://solidoodletips.files.wordpress.com/2012/09/photo-18.jpg

2 (edited by IanJohnson 2012-09-07 02:35:43)

Re: Acetone Vapor Bath

Here is a before and after.  The piece on the top was printed at the same time, at .1mm layers.  The rough patch on the top of the legs model is from the tweezers I used to get it out of the can.

http://solidoodletips.files.wordpress.com/2012/09/photo-20.jpg

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Re: Acetone Vapor Bath

That looks great and seems to be easy to do.
Regards
wolfi

I placed my order 08-18-2012, ID: 3676, it's hard to wait!

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Re: Acetone Vapor Bath

That looks pretty good, now if we could just get you to print something other than the cartoons my daughter watches we'd be okay.  wink   Interested to see the yoda

5 (edited by Jon 2012-09-07 05:17:19)

Re: Acetone Vapor Bath

This is excellent work.  Two things I'm interested in: 
How much mass was dissolved in the process?  Volume being the obvious method for measurement but perhaps more usefully approximated by measuring thickness reduced.

How long would it take to attain this level of smoothness with a .3mm print?

I imagine developing an agitator unit with a movable reservoir below to accelerate evaporation and a fixed platform above to hold the work, all sealed of course.

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Re: Acetone Vapor Bath

Since the part isn't submerged, the plastic all remains on the surface.  I suppose the surface tension is reduced enough that it flows together.  The surface isn't completely even, but there doesn't seem to be a noticeable amount of drooping.  That would be a hazard of leaving it too long, actual change to shape or thickness due to gravity.

8 hours was enough for the .3mm Yoda's head to fall off a few weeks back.  After about 4 hours, the other Yoda is looking shiny, but not especially melted.  There is less acetone in the can at this point, but I would think surface area is what matters rather than depth, at least until the depth reaches 0.

The pro machine warms the acetone, and has a cooling coil partway up the chamber to condense the vapor and keep it concentrated at the bottom.  I would be interested in doing something like this to reduce the exposure time to a few minutes.  That would make it easier to do a few cycles of vapor/drying. 

I would prefer some kind of agitation to heating.  Maybe some aquarium bubblers would stir it up enough, and some method of pumping ice water through some tubes for a condenser, and a glass lid so you can check on the progress without opening the contraption up.

7 (edited by IanJohnson 2012-09-07 06:12:09)

Re: Acetone Vapor Bath

Here is the Yoda after about 4 hours.  I saw the tips of the ears were starting to droop so I pulled him out.  I figure the .3mm texture has been reduced to something close to a .1mm print.  After he has had all night to dry (and I get back to the store for more acetone) I'll give him another shot.  It seems that if there is too much texture, you aren't going to knock it all the way down in one go without melting the model altogether.   You don't want the treatment to go more than skin deep, so that means a few applications with time to dry and harden back up in between.

http://solidoodletips.files.wordpress.com/2012/09/photo-22.jpg

http://solidoodletips.files.wordpress.com/2012/09/photo-21.jpg

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Re: Acetone Vapor Bath

Your results are compelling.  While the .3mm print is improved by the acetone bath, it's clear that the .1mm print with a bath seems to be the only way to approach an injection mold level of "smoothness."  Also, I hadn't really considered that the ABS would simply reflow without draining ABS, very good to know.

I have to confess, I'm a bit confused by your statement:

The pro machine warms the acetone, and has a cooling coil partway up the chamber to condense the vapor and keep it concentrated at the bottom.

What is the pro machine you refer to?  If this is somehow provided by Solidoodle I have missed it.

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Re: Acetone Vapor Bath

Those are looking good. You may be able to speed up evaporation by directing a small fan on the acetone (not the model for obvious reasons). This may help move the vapors around the can and decrease exposure time.

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Re: Acetone Vapor Bath

I was referring to the Stratasys smoothing station.  There is a PDF about it here - http://www.cimetrixsolutions.com/pdf/St … ations.pdf

They also have a burnishing station where you can sandblast a part with sodium bicarbonate.

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Re: Acetone Vapor Bath

i would assume ambient temperature would affect the speed, but i am not entrely sure, does vapor density increase in a closed container with more temperature ?
another thought I had, what if the the whole thing was placed on a lightly vibrating surface, it may help stir the surface and help evaporation, it may also help the reflowing performance on the ABS. ie .. allowing it move before it normally would.
I think my printer will arrive next week .. get used to my name, I'm going to be here a lot wink

12 (edited by IanJohnson 2012-09-11 04:50:56)

Re: Acetone Vapor Bath

I'm starting to get the hang of it.  It's best to get several exposures with plenty of drying time in between.  Ideally the effect will be kept to skin deep.  I've been putting the models on an upside down cup, which places them about 1" above the surface of the acetone.  I can see a definite difference in effect from bottom to top, corresponding with the change in density of the acetone vapor.  The zone only seems to be about 3" deep before it tapers off quickly.

It will take shorter exposures if I can make the vapor zone taller and denser.  Taking a cue from vapor degreasers, I could warm the pot enough to boil the acetone (100F or so).  Near the top of the pot I would run a coil or two of copper pipe with ice water pumped through it.  This would create a layer of cool air which will condense the acetone and keep the vapor concentrated in the bottom.  I would be doing this outside with the top off of the pot.

One thing I tried, which seemed promising, was to chill the model before placing it in the pot.  The process works by acetone vapor condensing onto the plastic and then melting it.  Chilling the model encourages more acetone to condense, which would increase the effectiveness of the less dense upper range of the vapor zone.  I would still like to get the vapor dense enough to require 30-40 second exposures rather than 30-60 minutes.

I printed this at .1mm layer height to give the smoothing process a head start.  I noticed that even after pulling the model out, it continued to smooth more as it dried.  So don't wait for all the lines to disappear before pulling it.  Take it out while they are still visible, and when you come back 30 minutes later, more of them will be gone.

Before- http://solidoodletips.files.wordpress.com/2012/09/p1160631.jpg
http://solidoodletips.files.wordpress.com/2012/09/p1160628.jpg

After one or two exposures-

http://solidoodletips.files.wordpress.com/2012/09/p1160633.jpg

Finished

http://solidoodletips.files.wordpress.com/2012/09/p1160643.jpg

http://solidoodletips.files.wordpress.com/2012/09/p1160639.jpg

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Re: Acetone Vapor Bath

a peltier with some plumbing could be useful perhaps by both cooling the top and heating the bottom simultaneously.
not sure whether fluid would circulate without pumping or if heatpipes would work, 2 peltiers and air heatsinks, one top and one bottom would work a treat i reckon and be simpler..
giving a 50C temp differential..

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Re: Acetone Vapor Bath

It would probably create less "blobs" along the model if it was lightly sanded before exposure, right?

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Re: Acetone Vapor Bath

Cleaning up as many threads, strings, blobs, etc as you can helps.  We only want to fill in the space between layers, which I guess would be something like .05-.1 worth of surface change.  The more you do this, the more fine detail you lose.  The more consistent the surface is to begin with, the less you will need to melt it to make it look good.

If you have a simple shape, I think you would be able to get some good results printing in .3.  If you sand it to knock the layers back a little and leave as much plastic dust in there as you can it should smooth up pretty well.  If you have something more complicated that would be a lot of work to sand, then it's better to take the time to print .1 so it is already as smooth as possible to begin with.

Something else to try might be adding plastic dust.  Maybe I could grind down some failed prints and roll a .3 model around in it, like battering a fish fillet.  If the dust is fine enough, it could fill in the spaces between layer lines and then get melted smooth.  That way the plastic for filling in the texture won't need to be taken from the surface detail.  Also it should require shorter exposures because you aren't trying to melt the the existing surface as much.  That would help protect thin features that might begin to droop from gravity, like Yoda's ears.

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Re: Acetone Vapor Bath

What about a thick abs-acetone glue that you brush on to fill the spaces?

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Re: Acetone Vapor Bath

I always had trouble controlling how much I put on, and then it would drip and run.  Thinning it out helps, but then you have to  apply a lot of coats to see the effect.  Then you might get more acetone on one part than the other, and different parts dry out at different rates. That's what is so cool about the vapor, is the application of the solvent is as even and constant as possible.

Maybe with the powder you can cover it, wipe off the excess and have some left over in the dips.  How well that works will depend on how fine the powder is, how big the gaps (.3 would work better than .1) and if there is a way to make the model a little sticky without causing lots of uneven clumps.

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Re: Acetone Vapor Bath

Ian,

Might I suggest a slightly different method that will likely help equalize (and increase) the depth of the vapor... ?  I skimmed through the thread, so I apologize if I misunderstand your processing method.

Instead of putting a raised cup into 1" of acetone, what about a deep cup submerged nearly to the brim?  The vapors would fall into the "pit" of a nearly submerged cup, filling the cup completely with vapors.

If the inner cup is nearly the same diameter as the retaining basin, the amount of acetone necessary should be minimized.

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Re: Acetone Vapor Bath

That sounds like a really good idea.  It didn't have as much effect when I just tried it, but I didn't have much time to let it sit and fill up.   I'll give it another go when I get home from work.  Hopefully I can put the model in without disrupting it too much.  I think I will still need to heat the acetone, but this would be a good addition to the design.  The smaller pot inside gives me something to lift up to get the model out.

http://solidoodletips.files.wordpress.com/2012/09/photo-23.jpg

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Re: Acetone Vapor Bath

Ian did that print without any support?  I want to try it!

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Re: Acetone Vapor Bath

I read a post on another forum where a guy was using a mixture of toluene, xylene, and acetone to smooth his printed parts. He was applying the mixture to the part with a preval sprayer.


He claimed it was as good or better than the smoothing machine, which he said costs around 40k!!

The mixture amount was:

45% toluene
45% xylene
10% acetone

Apparently, the toluene and xylene are used as evaporators so the acetone doesn't reside on the part long enough to turn it to sludge (like the first Yoda)

I bought a container of each chemical at Sherwin-Williams and the preval sprayer I got from Autozone. It is the kind with the glass jar attached at the bottom (9$)

But, I have no printer yet (awaiting SD)...and so no parts to test it on.

Anyone tried this?

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Re: Acetone Vapor Bath

I tried acetone with a preval sprayer, and it seemed like evaporation was too fast.  The acetone dries out before it has much of a chance to melt the plastic.  If I keep the spray going, then it gets wet enough to start to have an effect.  At that point, even application starts to matter.

What I like about the vapor is that the condensation makes for finer, more even droplets compared to atomization.  The coating of the acetone is very thin, just a bit of dampness.  However that dampness doesn't get to evaporate so it keeps working on the plastic until you pull it out.  The key is to get the model out before the plastic melts to a depth where it can weaken the structure.  Let it melt deeply enough for the surface to start to move and spread, then dry it out.  Once dry, the acetone has to start over again and smooth the partly smoothed surface a little more. 

If I can make the vapor dense enough that the exposure time is only a minute or so, then it will be easier to judge how long to keep it in.  I might also make a drying station that is some kind of box with 2-3 computer fans blowing into it.

I don't anticipate spending more than the cost of a fountain pump and some tubing.  Everything else I need I already have.  I plan on ventilation being provided by the great outdoors.

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Re: Acetone Vapor Bath

Cool. That's going to be a nice solution. You've already produced some really impressive results.

After some further googling, it appears that the he may have been using xylene and toluene to lower the overall evaporation rate of the mixture (not increase it, as I stated in the previous post) That way the acetone would have a longer working time before it evaporated. Here are the evaporation rates relative to ether, which is assumed an evaporation rate of 1:

The higher the number, the slower it evaporates.

Xylene (13.5)
Toluene (6.1)
Acetone (2.1)

I hope to give it a try and report back once I'm able print some parts smile