How to get a smooth finish on a PLA printed part

[jsc]

How do you sand in the crevices, like the eyes and ears?

[Artenen]

Paint works ok

I got the smooth on stuff... works but eh..

Then I can across Tetrahydrofuran as it works like acetone. Here is a video -

https://www.youtube.com/watch?v=KJYaqaUr7iw

Vapor Smoothing and Polishing PLA with Tetrahydrofuran (THF) Article http://www.protoparadigm.com/news-updat ... furan-thf/

[Tim]

Do you mean that you've tried the THF, or just heard about it? I used a Methylene Chloride vapor bath on PET+ with pretty good results. I've heard that works on PLA, too, but I haven't tried it with anything other than PET+. I used an electric griddle that I keep for soldering work, and put a cheap disposable aluminum serving container on that, covered with a glass plate (so I can see what's going on). I put the printed piece on a stand, filled the bottom of the container with a small bit of Methylene Chloride, put the glass plate over it, and turned on the griddle. After a minute or two the Methylene Chloride boiled off, and the print had a nice polish to it (picture on https://www.thingiverse.com/thing:276167). I'll have to try the THF.

[Dave K]

Another reason to use nitrile or neoprene gloves...since this solvent is so readily absorbed through the skin, anything dissolved in the solvent is likely to get carried into the skin with it. I just found out about this stuff and I don't know what's available online, but if there is a choice between industrial grade and laboratory grade, get the laboratory grade solvent. At least you'll know it doesn't have significant impurities, just in case it gets on your skin in spite of wearing the right kind of gloves!

[Artenen]

I've only just heard about this now so I haven't tried THF yet. I do know that pvc pipe cleaner has it in it so I may also test the vapor method using that as it is cheaper and readily available everywhere. Of course proper protection, nice breather mask, venting (outside), fire extinguisher, buddy system will be used for this test. All the vapor stuff is really dangerous so I'm not taking any chances. I'll try and shoot some video of it if I get a chance and will report back.

[Artenen]

Ok the pipe cleaner worked awesome! Here is my video -
https://www.youtube.com/watch?v=0x7bezgJJaA

[jimc]

i like the country porn music. its sorta snappy

[Jules]

Awesome-est news! Something i don't have to buy.....got at least a couple of gallons of PVC cleaner out in the garage! I was wondering if you could vapor smooth a PLA print the way you do the ABS with acetone.

What temp did it take to boil it off? (I'm just wondering if it could be used outside in the sun, without heating it?)

[msmollin]

Be *extremely* careful with THF vapor. Unlike acetone, the vapor is rather explosive. THF is normally diluted/mixed with other chemicals to keep the explosiveness down, but when you boil it those separate out.
--End PSA--

I've had good luck with high build primer. As others have mentioned, it very much depends upon the plastic, but also the surface of the plastic. For example, if you are printing with support material, support material will mar a flat surface real good. For that, I've normally started with 100 (or even as low as 80) to try to get an even surface, then step up to a 150 to smooth it. Then I apply 2-3 coats of the high build primer, then sand at 220, then more primer if you're unhappy with the first round, then more sanding. I'll then normally do 2 light coats of paint, and depending on what I'm going for, an 800 light grit sand on the paint followed up by a clear coat. Some paints coat better than others though, so not all require the final light sand.

If you don't have support material to deal with, many times I'll start right at 150 and go from there, and it normally won't require more than 2 coats of primer to cover. Also be sure to wash the pieces off and allow them to full dry before starting the next step to not get little plastic bits stuck in the paint.

I always sand with a particulate mask on, and basic safety goggles, after my dad had to have a splinter removed from his eye. Not a fun time, so better safe than sorry. No need for a full-on P100 respirator though until you get the to painting part.

[Artenen]

It boils at 150 Degrees F. The first stuff I used didn't have THF and the vapor was heavier... it also was slower (yellow can stuff) and more controllable. The tan bottle of PVC primer has THF in it and oh my gosh it will smooth a part in 8 seconds flat.. I wrecked a part because I pulled it out with my fingers and the thing warped. The non THF stuff held shape under vapor.

Either way these fumes are super bad... get a good breather mask rated for chemical vapor solvents (not just pesticides) before doing this. Again, do not do this in the house or your wife will literally kill you on the spot. Even in the garage that is vented I have a small fan blowing the fumes away from me. Don't skip any precautions here people or it could kill you. This isn't "wear your safety belt" kinda warnings, it's "if you breathe this stuff, it can kill you" kinda warning.

Man, the parts are ultra shiny with THF though... I did get a vegetable steamer set today to do larger parts with more precision.