PLA vapor smoothing

Discussing what we do with our prints after we make them (clean up, integration, etc)

PLA vapor smoothing

Postby PxT » 2013-Jun-Thu-14-Jun

Interesting article on vapor smoothing PLA. Up to now I was only aware of the options that were available for ABS. Glad to see that someone has discovered a compatible solvent for PLA!

http://www.protoparadigm.com/blog/2013/ ... furan-thf/
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PLA vapor smoothing

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Re: PLA vapor smoothing

Postby mdfast1 » 2013-Jun-Thu-15-Jun

Awesome, I kind of wish there were some better pictures along with it, hopefully someone picks some up and takes better pics.
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Re: PLA vapor smoothing

Postby PxT » 2013-Jun-Thu-15-Jun

THF seems to be a bit more difficult to acquire. Definitely not as easy as going down to the hardware store and picking up some acetone.

With acetone, I assume you take any remainder that is left in the vessel after smoothing and save it to use again? THF looks to be pricey so that would definitely be advantageous, although there are some notes about not letting it distill. I wonder if that would be a problem over multiple re-uses?
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Re: PLA vapor smoothing

Postby eckerput » 2013-Jun-Fri-13-Jun

With THF you also have to be careful about high explosive peroxides forming. From the MSDS...

It is normally stable, however, prolonged storage, and exposure to air and light may cause formation of unstable explosive
peroxides especially when anhydrous and unless it is inhibited against peroxide formation.

Allowing THF to evaporate, exposing it to air, and exposing it to light (all of which would occur during vapor smoothing) degrades the stabilizer and could lead to peroxide formation. Check out this chemical safety sheet from University of Illinois http://www.uic.edu/depts/envh/HSS/Documents/Peroxide%20Safety%20Fact%20Sheet.pdf. In their system THF is a class B peroxide former.
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Re: PLA vapor smoothing

Postby PxT » 2013-Jun-Fri-15-Jun

Well, reading that was enough for me not to ever want to mess with THF.
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Re: PLA vapor smoothing

Postby Bob-StPaul » 2013-Jun-Fri-20-Jun

I might be tempted to try the hand polishing with THF - but like ether - I don't like the idea of heating it outside of a vented safety hood...

It's also much less shelf stable the acetone. That UIC document says 6 months after opening it should be discarded (in a safe manner.)
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Re: PLA vapor smoothing

Postby rsilvers » 2013-Jun-Sun-23-Jun

Given the cost of the solvent, this is impractical.

It is over $200 per gallon.
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Re: PLA vapor smoothing

Postby isp3p » 2013-Jul-Wed-22-Jul

If you're a hobbist, just forget about THF, if you can even get it in the first place. You have to pay a professional good money to safely and properly dispose of it.
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Re: PLA vapor smoothing

Postby printedsolid » 2014-May-Tue-15-May

I've had some success using ethyl acetate for vapor polishing PLA. In the US, you can find it in big box stores as MEK substitute (NOT MEK). It might be pricier in other countries with different chemical regs. I do have pics on the blog, but it won't let me post it as a new member.
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Re: PLA vapor smoothing

Postby KDog » 2014-May-Tue-16-May

Please keep in mind that these are dangerous chemicals you are messing with. Some of them are acutely toxic and dangerous. In the case of ethyl acetate you can damage your mucous membranes just by breathing it. I've commented on several of these types of threads. How far are you willing to go to "fix" a fundamental characteristic of FDM printing? In my opinion you are much better off trying or designing new types of printers. FDM prints can be made smoother by optimizing your printer. You will never end up with the print you want if you are so concerned by the layered look.
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Re: PLA vapor smoothing

Postby RetireeJay » 2014-May-Tue-19-May

KDog, can you provide a reference that says ethyl acetate is bad? According to the Wikipedia article, it is found in many things including nail polish and perfume. Their summary statement on safety is "Given that the chemical is naturally present in many organisms, there is little risk of toxicity."

However, I worked in a research environment where a chemist used ethyl acetate as a solvent, and I will certainly state that in high concentrations the stuff is not pleasant. In general, ALL organic solvents should be handled carefully so as to avoid breathing concentrated vapors. (But some are MUCH worse than others.) For that matter, melting plastic gives off vapors too. We all should always avoid situations where breathing fumes makes us feel uncomfortable in any way.
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Re: PLA vapor smoothing

Postby printedsolid » 2014-May-Tue-19-May

It's all about exposure. I wear a respirator mask, solvent gloves, and run the process outside. It's also worth pointing out that the smoothing process takes seconds. So, if you're careful, exposure is quite low. Read safety sheets. If you don't feel like you can do it safely, don't do it. By the way, there are some incorrect ethyl acetate datasheets floating around on the internet that list hazards for MEK instead of ethyl acetate, so I'd go with the MSDS provided by the provider of the chemical you are using if you want to ensure it is accurate.

before all.jpg

All of the octos lined up. I believe these were all printed at 200 microns with a 0.8mm diameter nozzle. Materials from left to right:Blue Grey colorFabb PLA/PHA, colorFabb XT, colorFabb woodfill coarse, Black Madesolid PET+, Pink PLA.

before pinkie.jpg

Here's a solo shot of the pink one.

after all.jpg

Overall view of the whole bunch after the polishing. The two PETs (XT and PET+) polished much better than the pictures show. The PLAs turned out pretty nicely as well. I've since done this at higher resolution and lines are well obscured.

after pinkie.jpg

Here's another solo shot of the pink one after her vapor bath.
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Re: PLA vapor smoothing

Postby KDog » 2014-May-Wed-01-May

Here is a link to the MSDS - http://babec.org/files/MSDS/EtAc.pdf

It's always a matter of concentration with chemicals. We come in contact, breathe and ingest many of these chemicals every day at safe or physiologic concentrations to little or no effect. The problems come when we are dealing with the concentrated stocks.

There was a video going around a few months ago about using carburetor fluid for making your pla prints flexible. The video shows a guy sitting at his desk in his home office, a closed window in the background, spraying carb cleaner into a can so that he could drop parts in it to make them flexible. The thread was going on and on without anybody mentioning the dangers of doing this and everybody saying how cool it was and that they were going to run out and get some right away. Why does safety come second when we are talking about this stuff?

Acetone baths for ABS went from heating out in the garage to folks with cans of it on their gas stoves in their kitchen. This does not further the field and comes with risks that we really should not be encouraging.

Yes, I work in a field where I come in contact with these types of chems, and worse, every day. Safety is second nature to me around them. I've been injured in the lab twice in my career....both times by the actions of others. I can't help but mention it to folks when I see them doing unsafe things. Not to mention it's part of my job description as well.
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