Acetone Vapor For PLA?

Can the acetone vapor method be used for smoothing a PLA printed part or does that work only for ABS? If not, how can PLA be smoothed?

Alternately, can ABS be used to make a lost wax pattern for casting similar to PLA without burn-out problems?

Randy

Randy I don't believe acetone will affect PLA like it does ABS. The solvents for PLA are nasty as far as I'm aware. If you do a search for vapour polishing you should be able to find more, as that's what the technique is often called. PLA can be machined in your chosen method to obtain a smoother finish. Acetone will dissolve ABS, and the solvent is commonly used both for vapour polishing and to create a juice that can be painted on the build platform to increase the stick. I tried that juice for a while but wasn't impressed so use different things these days.

I'm not sure why you want to use ABS instead of PLA for investment casting, but many of these plastics produce some pretty nasty fumes when heated to very high temperatures. I believe PLA is reasonably innocuous in that regard, however I'm not an industrial chemist so treat that advice accordingly!

"I'm not sure why you want to use ABS instead of PLA for investment casting"

Because of the polishing question Pete.

Randy

It appears that all PLA is not equal. Some of the better ones are alloyed with other materials (such as ABS) to improve strength and other physical properties. So yes, you can acetone polish certain formulations of PLA, just not pure PLA.

Randy

rhoward said:

It appears that all PLA is not equal. Some of the better ones are alloyed with other materials (such as ABS) to improve strength and other physical properties. So yes, you can acetone polish certain formulations of PLA, just not pure PLA.

Randy

Click to expand...

Can you provide an example of a filament where ABS and PLA are mixed in the same filament? I have never heard of such a filament, and while the sector is changing daily, I can assure you that if it does exist, it certainly would not represent "some of the better ones", and would instead be a niche product. Even if you could find a filament like that, it wouldn't necessarily mean it could be vapour polished with acetone. Different materials are quite commonly added to a PLA base filament to provide specific properties of that additive. That does not necessarily make them "better" as a filament, it's merely the fact they offer those properties. PLA and ABS are completely different plastics, both can be vapour polished, it's just that the PLA is more difficult to do and requires different solvents. I have had PLA soaking in acetone for days for example and it is completely unaffected.

I was likely wrong about ABS being added to PLA but there are PLA filaments whose mechanical properties are augmented by adding other substances to create a blend and that was the intended point of my last post. Colorfabb is one example and according to a couple of web blogs it will polish using the acetone vapor method. Here is what Colorfab says about their product: "Colorfabb developed its own unique blend of PLA/PHA which results in a tougher and less brittle PLA 3d printing filament. PHA (polyhydroxyalkanoate) is like PLA a bio-polyester, so our unique blend is still 100% biodegradeable. This material is available in a huge variety of colors, take a look in our PLA/PHA portfolio."

Randy

Here is another quote also recommending Colorfabb and it does mention the additive of ABS to PLA. I cannot personally verify the accuracy of what is said here.

"And remember this wont work with cheap brands of PLA due to their high PLA content and lack of HIPS/PHA/ABS in the PLA blend (remember pure PLA does not smooth chemically with acetone and is more brittle and weaker than the blends anyways so you are better of using the blends even though they are unfortunately more expensive). I know it works for Colorfabb PLA. I have not used any others so cant speak for the millions of other brands of PLA out there. And remember this wont work with cheap brands of PLA due to their high PLA content and lack of HIPS/PHA/ABS in the PLA blend (remember pure PLA does not smooth chemically with acetone and is more brittle and weaker than the blends anyways so you are better of using the blends even though they are unfortunately more expensive). I know it works for Colorfabb PLA. I have not used any others so cant speak for the millions of other brands of PLA out there."

Randy

I have no idea where you pulled that statement about "blends" from, but it sounds like some forum. You asked if acetone can be used to smooth PLA. It cannot. You then told me that in fact there are "blends" out there that contain ABS, apparently, and so can be vapour polished. Despite the company in question saying it is PHA they add to their PLA. PLA is not ABS.

The market for filament is becoming very competitive, and although the machines to extrude the filament are relatively large and complex, the barriers to entry are reasonably low. As a result every supplier wants people to believe their filament is the best and/or contains some magic ingredient that will differentiate it from the competition. Adding something else into a PLA filament does NOT necessarily make it a better filament than one without something added. Indeed I do know of some of these "exotic" filaments that were dreadfully out of tolerance and would often produce extrusion issues.

Your "questions" seem to be more statements where you appear to have all the answers, so I'll leave you to it then.

Use Ethyl Acetate to smooth PLA. You can get it at the hardware store - search for "MEK substitute" in the paint stripper section. This works great.