SLA 3D printing with resin typically means rinsing parts with IPA (isopropyl alcohol). That process results in cloudy, used IPA containing a high concentration of dissolved resin. The dual goals of cleaning and reusing IPA are important ones, and we have to say, [Jan Mrázek]’s unusual experiment involving a UV source and slowly-rotating paper tube to extract and cure dissolved resin might look odd, but the results are definitely intriguing.
The best way to dispose of liquid resin is to cure it into a solid, therefore making it safe to throw away. But what about resin that has been dissolved into a cleaning liquid like IPA? [Jan] felt that there was surely a way to extract the dissolved resin somehow, which would also leave the IPA clean for re-use. His solution? The device shown here, which uses a cardboard tube to pull dissolved resin from an IPA bath and a UV source to cure it onto the tube.
Here’s how it works: the tube’s bottom third sits in dirty IPA, and UV LEDs shine on the top of the tube. The IPA is agitated with a magnetic stirrer for best results. A motor slowly rotates the cardboard tube; dissolved resin gets on the tube at the bottom, UV cures it at the top, and the whole thing repeats. Thin layers of cured resin slowly build up, and after long enough, the roll of cured resin can be thrown away and the IPA should be clean enough for reuse.
So far it’s a pretty successful test of a concept, but [Jan] points out that there are still some rough edges. Results depend on turning the tube at a good rate; turning it too quickly results in IPA trapped with the cured residue. On the plus side, the UV source doesn’t need to be particularly powerful. [Jan] says that Ideally this would be a device one could run in a sealed container, cleaning it over one or two days.
Resin printing is great, but it’s a messy process, so anything that makes it less wasteful is worth checking out. Got any ideas for improving or building on this concept? If so, don’t keep ’em to yourself! Let us know in the comments.
Ok im probably going to have to try this one…
Centrifuge?
Distill…
For those that failed to read the linked article:
I came up with the following device – it is a slowly rotating paper roll forming drum, that is by 1/3 submerged in the dirty IPA. On top of the devices are high-power UV LEDs. The whole device is closed in an air-tight box with the IPA. As the paper tube slowly rotates, a thin layer of the dirty IPA forms on it. It should have enough time for the IPA to evaporate. Once it reaches the top, the UV LEDs cure it. In this way, we simulate what a printer does – curing thin layer by thin layer. After a while, we should get all the reactive components from the bath onto the roll in a cured form.
Pretty sure they were contemplating alternative methods of cleaning the IPA, not making guesses about this process.
If the UV is warm its evaporiting the IPA at the same time, almost need a cold plate and a sealed system.
Well, that’s exactly what is written in the linked article: “The whole device is closed in an air-tight box with the IPA.”
I wish it worked that way, but it doesn’t. I’ve tried distilling IPA with low heat (a heating pad) over a long time and it didn’t work at all. After 2 weeks in a totally air tight 2 container system, I didn’t have a single drop in the second.
If it were that easy then this process wouldn’t be needed.
Recycling India Pale Ale?
No thanks, I have enough trouble cycling it the first time.
B^)
Anybody want some gently-used IPA? Still has a similar color. Even has a bit of a head on it (if it’s fresh)
Dude, you’re indicating a pre diabetic condition if you’re excreting foamy pee.
You would too if you 6 IPA’s deep
What happens if you put a uv light on your contaminated IPA? Seems like it would harden and you could pull it off the top.
You may end up with a gel which will under vacuum distillation turns into a stiff lightweight foam. Not unlike an aerogel.
Or it would settle to the bottom.
Either way, running IPA with cured resin particles through a filter (funnel with filter paper) would probably be faster, less hassle, and have less problems with evaporation.
If the IPA is saturated enough, it turns into cursed Jello.
Wasn’t that the plot of an episode of “Phineas & Ferb”?
Pretty much. (Without the IPA, of course.) It’s the episode called “Day of the Living Gelatin.”
Yes. Yes it was.
I have always called it “forbidden Jello”.
Depends. I’ve done that to what I thought was settled out resin in my IPA tub, and got what was a crude aerogel of resin suspended in the IPA, making the whole thing the consistency of halfway-set jello. There was zero possibility of taking the resin sludge out of the IPA bath.
The linked blog post contains a section “What have people already tried?” that exactly discusses this.
This is not a panacea, the IPA will still contain components of the resin. There’s not really any easy and cheap way to purify contaminated IPA. The most accessible way to do so would be fractional distillation, though possibly a reverse osmosis system would be affordable (doubt it though).
That’s not quite the point. He’s not trying to purify it, he’s trying to reduce the saturation so it will rinse more resin off of 3D printed parts. Recycling doesn’t have to return things to their initial condition, it just has to make them useful again.
Bigclive just did a teardown of almost exactly what you describe, and the first comment on that video is using it for this exact purpose, cleaning resin from IPA.
https://youtu.be/x4HsN07emYw
What if you just lean into the problematic part and try distilling the alcohol and leave behind the resin?
That works too. As does flocculants. I like using a ceramic filter and a couple of 5 gallon buckets. I also will salt out the IPA to remove water too.
With our formulas setup, we just take used stuff, put it in jugs, leave them outside for a few weeks. Run thru coffee filters, clean ipa.
What do you use to measure the cleannes of the IPA? The linked blog post disuccusses it and gives the following conclusion:
“Another approach is to let the resin sit in a dark container for a long time so the dirty part settles. In my experience, what settles are only the pigments and fillers, but most of the components of the resin are left in the IPA. When you put paper in a bath cleaned in such a way and expose it to light, it will actually harden. So, this approach didn’t work for me. You are still left with a dirty bath that will only make your prints sticky.”
This is why I have barely used my resin printer, it is just to much hassle compared to FDM and most of what I print really doesn’t need the detail resin provides.
That’s what has kept me from buying one. I mostly build replacement parts, not detailed figurines. On top of this, PLA is tougher and less brittle.
The water soluble stuff is actually pretty nice, no alcohol needed. I add a little soap (simple green) to my water and use a super soft brush to get the residue off.
I got tired of the endless tuning on my fdm printers, and I don’t print very often so the price difference is negligible.
But what do you do with contaminated wash water?
I just pour mine into a bucket and let the water evaporate. In summer the sun will harden the resin so I keep it next to a window. Rest of year we don’t have sun here so every once in a while I shine my uv light on the remaining goo.
One of my many projects is to build a resin printer that eliminates the need of IPA in the first place.
Don’t resins that are water washable already exist?
Yes, but in my limited experience (1yr with resin and only 6 or so soups) it takes significantly more brushing to get the leftover resin out of any details of the model. Considering the rinse water also needs to have all the resin solids cured and filtered before disposal, it really only saves the cost of alcohol not the hassle.
I’ve had really good luck with water washable. The first batch would crack easily bit bottles since have been consistent and easy to work with.
erffrfez@gmail.com
Am I missing something? When did alcohol become a precious commodity? I could buy an awful lot of alcohol for what it would take to set up a recovery process like this.
If you read the blog post, you will learn the main motivation is not to save resin, but actually to solve the problem of disposal of the dirty bath.
Isopropyl is made from propane, it’s technically a propane accessory.
Hank Hill approves the previous comment.
The point is to not be pouring poisons or potentially drain clogging chemicals down the drain. Same reason I cure the water I use to wash my resin.
Why not phase separate or vacuum distill off the IPA leaving the resin for reuse/recycle?
Let me quote the linked blog post: “The last approach is distillation. I haven’t tried this as it’s relatively dangerous when done wrong, has high input costs, high running costs (come on, 1 L of IPA costs 2€!) and also, I am not sure if the boiling point of IPA is below the boiling point of all the volatile parts of the resin.”
For those that failed to read the linked article:
I came up with the following device – it is a slowly rotating paper roll forming drum, that is by 1/3 submerged in the dirty IPA. On top of the devices are high-power UV LEDs. The whole device is closed in an air-tight box with the IPA. As the paper tube slowly rotates, a thin layer of the dirty IPA forms on it. It should have enough time for the IPA to evaporate. Once it reaches the top, the UV LEDs cure it. In this way, we simulate what a printer does – curing thin layer by thin layer. After a while, we should get all the reactive components from the bath onto the roll in a cured form.
Great attempt. I may try in the future. Perhaps a paper towel roll instead of TP? Would that result in a faster process?
If your interest is more in safe, convenient disposal than recovery there is a little known secret.
IPA which is saturated with resin has all the important properties of flammability, energy density and consistency to make it within the specs for fueling your neighbors’ cars. Go ahead, stick it in their tanks. They will just think they have been visited by the magic MPG fairy. Never try it in your own car though, something about it’s chemical properties just aren’t right for your engine.
This is a great way to eliminate waste while helping your neighbors. At least until we all switch to electric. After that I believe it will be time to look into it’s ability to prevent algae growth in the neighbors’ pools.
I just plonk a transparant airtight container, like a drinks bottle, on the window sill for some time. the sunlight cures the resin, which sinks and allows for other resin to cure.
after 3 days to a week, depending on how sunny it is, the liquid turns clear in the middle of the day, and you can either pour it all trough a coffee filter, or pump off the clear IPA. consolidate the rest in the window sill again and a think lump will form at the bottom, which can be tossed or squeezed into a brick, extracting more IPA.
Yeah. Seems like the easiest way to do it.
Not all problems need complicated solutions.
can this be made to do double duty?
get the parameters right enough, and pick a shape to rotate that you actually want to make, and it seems at least ‘possible/worth investigating further’ that you could end up with a plastic shape that is actually useful.
This could be easily implimented to extend the life of your IPA between deep-cleanings. I wonder if it would be better to isolate the system so that stray light doesn’t cause sludge to form at the bottom. Maybe you could use a pump to flush the IPA over the roller in a separate area that drains back into the regular tank… You could sell an add-on to any existing tank system.
P.S. something similar that I thought should be shared: Check out the Onulis WRAP.