I recently printed a vermicomposter in PETG. It consists of a bottom reservoir which is supposed to catch leachate from the above compartments. I’m not sure the rate at which this will fill up, but the leachate is supposed to be diluted with water and used as nutrients from plants.
However, the reservoir leaks from the plug and from the front leg slots, at least when the reservoir is filled completely up with water. The leak from the plug I seem to have fixed with a combination of an o-ring and some PTFE-tape, but for the other leak I’ve been thinking of coating it with epoxy resin.
My challenge is actually finding such a resin, where the finished, cured product is food safe (since it will eventually find its way into the plants I intend to eat). Locally, I’ve not been able to find anything that is certified food safe, only various epoxy fillers and primers for boats.
The local 3D-print shop recommended this product which I could get through them: https://siraya.tech/products/siraya-tech-aegis-coating-systerm-for-resin-filament-prints But I’ve found some less than favorable reviews for that one in particular.
Anyone with experience water-tightening containers like this?
I’d flag this as something to spend money on instead of time on… Even good manufacturered plastic absorbs odor over time. My guess is the functional life of this will be limited and you will need to reprint it enough times that you’re not really being so ecologically friendly anymore. A commercial product might work better and last longer.
Bees wax
Oh, that is an interesting idea that I hadn’t thought of. I might be able to buy it from a local beeskeeper, and I think I have a small amount lying around somewhere I could test with.
Warm it up enough to roll it into sheet and heat gun it into place. Food safe and waterproof plus should hold up for a long time
Which slicer do you use? There is a setting a that can improve water retention capabilities with just a check box. I think it’s called “stagger perimeters” in Bambu for example. Also use at least 3 walls. Some good tests and examples on YouTube by “Designed to make” if you’re curious.
I am using PrusaSlicer. Not sure if that check box is present in that, or if it was added in OrcaSlicer or BambuSlicer.
I might’ve printed with only two walls, I will need to check tomorrow when I’m at the correct machine. And thanks for the video recommendation, I will be sure to check it out!
Prusa published an article about it: https://help.prusa3d.com/article/watertight-prints_112324
Cheers - seems there are multiple things I could have done. I would rather avoid having to do a reprint, but it may be necessary.
Upon closer inspection, I think the geometry of the bottom part is designed in such as way that it comes out with a lot of cavities (it is slanted, requiring multiple steps). It could be that it will be very difficult print properly to begin with.
Max CLR has a two part food safe epoxy resin that’s good for prints and other things
Three walls of PETG should be water tight. if not, you are under extruding.
I might’ve printed with only two. But I’d like to avoid having to reprint, if possible, and instead fix it with some post-processing. I think the leakage is actually concentrated on certain points near the front leg slot, so it does not seem to generally seep through the entire bed.
I’ve made a couple drinking vessels with food-safe epoxy. Been meaning to try food-safe polyurethane too. And a guy who makes drinking horns has told me that shellac is naturally food-safe too. I don’t 100% believe him but I used it on my horn anyway and water tastes okay out of it.
Locally, I’ve not been able to find anything that is certified food safe, only various epoxy fillers and primers for boats.
Call the manufacturer of the locally-available epoxies and ask them what they recommend.
I went looking for contact info for one common brand as an example, but found instead this product support article that suggests, to me at least, that their “limited food contact”-rated epoxies would be good enough for your use-case.
(I never did find a phone number or email for product support, but they do at least have a chat widget, so… 🤷)
Aquarium silicone?
Didn’t think of aquariums. Would assume this should be food safe, since it will be in contact with environment of living things. Would you happen to know whether it has any good adhesion to PETG?
Unfortunately I do not. I should have checked before posting, sorry.
Oh no, don’t worry - it was a great suggestion, and I’ll check it out for myself, just asked in case you already knew :) Thanks!
I personally would not consider superglue harmful enough to worry about plants seeping enough of it to affect the health of me eating the plant, and it’s not food grade. I’ve used it to fix cracked humidifier reservoirs in a greenhouse for example. That being said, most epoxy resin dries food grade. I don’t think you’d have to search hard for a very well performing Resin with food grade search term swapped with dining surface or some frequent use that requires food grade.
Superglue is used in all kinds of stuff that we come into contact with every day. Dentists and orthodontists even use it inside our mouths.
I would have assumed that dentists do not use the same consumer-grade stuff you buy in your local shop. Do you know for sure that they do?
I don
t know if its the exact same as consumer grade glue, but it`s definitely CA glue.
I personally would not consider superglue harmful enough to worry about plants seeping enough of it to affect the health of me eating the plant, and it’s not food grade. I’ve used it to fix cracked humidifier reservoirs in a greenhouse for example.
I would want to avoid something that leeches off into the water. That said, I am going to dilute it quite a lot since the stuff will be very concentrated. Super glue could be a little expensive for this though? I think coating the whole bed would take multiple small containers.
That being said, most epoxy resin dries food grade. I don’t think you’d have to search hard for a very well performing Resin with food grade search term swapped with dining surface or some frequent use that requires food grade.
I know very little about epoxy resin, but that is what I often see - but is it really basically the same stuff that is used to repair boats as people use for decorations? The safety data sheets for the components are always pretty rough, but they of course say nothing about the cured state.
You seem to be worried about water eroding away resin or something to that effect. The bonds are strong enough that’s basically not a concern. It’s kinda like being worried about a Teflon storage medium because it’s got a bad safety sheet.
My recommendation is find something that’s waterproof on curing that can handle both ends of the pH spectrum and call it a day. You aren’t worried about abrasives.
Edit: UV too, depending on where it will be could be a concern, but petg isn’t UV ready either.
