popcorn salt annealling is the shit

[solarbird]

If you anneal your 3D prints, like, ever, that whole “pack it in popcorn salt” trick works an absolute treat. You still get a little shrinkage on the X and Y, and an even smaller (but borderline) height climb on the Z, but it’s way WAY less than without it, and otherwise the geometry just stays perfect and none of the details go anywhere or anything. I’ve been putting off trying this for months – partly because I don’t really do that much annealling lately – but now I’m like “wow okay I really learned something today” and wish I’d done it a few months ago.

It’s pretty easy. I put a layer of salt in a glass jar, then placed an ordinary plain generic PLA object at the bottom, before packing the rest of the jar with more popcorn salt as tightly as I could, tapping it a lot to make sure I got the best possible surrounding of my object, and using the lid to put some pressure on the salt from the top.

Then I hit the whole thing with 70°C for an hour (15 minutes preheat, 45 minutes at temperature), took it out and measured it, then repacked and reheated the same object at 80°C for 90 minutes (after preheat) and it’s fine, modulo a lesser degree of the inevitable X-Y shrinkage. The second heating cycle changed nothing dimentionally, despite the higher temperature.

If you’re using a PLA that anneals to a higher glass point after annealling and you have reason to care about geometry, this is a great solution. You can even re-use the salt. I wouldn’t eat it after using it forthis, of course, but you can use it all you want for annealling.

Anyway, this is a great trick and if you do 3D printing you should try it.

Posted via Solarbird{y|z|yz}, Collected.

Comments

[armiphlage]

What's the purpose of the salt, versus just annealing in a warm oven?

[solarbird]

Structural support!

If you've ever tried to anneal something where geometry matters - say, if for some dumbass reason, you wanted to make something shaped like an L. Or, say, a sculpture with an extended sword. Annealling that shit is a nightmare.

Or you can pack it in popcorn salt and it's easy! :D

[vatine]

I guess any fine-grain salt would work? Or is there something specific additive in popcorn slat that makes it extra good?

[solarbird]

As far as I know there's nothing special about it other than the fine grain and being a salt that doesn't react with PLA. (As far as I know, other printable plastics don't get annealed.) But it's readily available and cheap, so.