Lowest-mass smoothing techniques for 3D PLA prints?

[Winston]

Anyone with any experience with lowest-mass smoothing techniques for 3D PLA prints, smoothing methods which optimally might also strengthen the print? Absolute requirements are that the technique cannot alter the dimensions of or distort the print. I'm thinking thinned epoxy with a microballoon filler. Anyone tried that? Also, phenolic or fumed silica?

EDIT: from elsewhere, "phenolic micro balloons are much easier to sand than fumed silica" - looks like it's phenolic microballoons then.

 

[boatgeek]

Definitely microballoons are the epoxy filler that's easiest to sand. They won't add much strength though. I also wouldn't thin the epoxy, just mix in microballoons until it's the consistency of creamy peanut butter.

 

[Winston]

Definitely microballoons are the epoxy filler that's easiest to sand. They won't add much strength though. I also wouldn't thin the epoxy, just mix in microballoons until it's the consistency of creamy peanut butter.

Thanks. The reason I mentioned thinning is to avoid a too-thick coat and perhaps to have some infusion into the PLA shell to add strength. It takes only a very small amount of added alcohol to greatly thin epoxy from what I've read although that also reduces its strength and lengthens cure time. I've also read that microballoons reduce cure time, so maybe they'll cancel each other out. ;-) Isopropyl alcohol (IPA) is used to clean printer beds, so I'm going to test some 99.9% IPA I have for solder flux removal on some scrap PLA prints to make sure there's no significant softening or layer separation. I'll also test that IPA on the phenolic microballoons.

 

[Winston]

FAIL. Alcohol diluted mix using a tiny amount of 99.9% IPA to significantly thin it takes days to "cure," but it's not the time to cure that's the issue, it's that the cured mix remains very sightly rubbery which doesn't lend it self to sanding. Plus, even the thinned mix does not brush on evenly/smoothly.

Looks like I'll use the method I saw in a YouTube video - multiple coats, if needed, of easily sanded high build primer with sanding in between each coat - sand each time until PLA layers show up with primer in between.

 

[Oberon]

Not too many great options for PLA unfortunately. If your printer can handle it, give ABS a try - it's acetone soluble, so painting on acetone (literally you can apply it with a paintbrush) does a nice job of smoothing and bonding the surface.