I’m trying to do the impossible—create a seal that’s completely airtight and watertight. We’re talking about something that could work for bottle caps, weird project seals, or basically anything that needs to keep stuff in or out.
My current hack is pretty old-school. I made a cap with a super-strong sliding surface that gets mega-tight when you twist it. The inner ring squeezes so hard against the bottle lip that it’s almost perfect. Right now, it stops water completely, but tiny bits of air still sneak through. Ugh!
I want to go hardcore on this. I’m looking for crazy ideas—like designs with crazy-complex tooth patterns that cut into together, or ways to crank up the pressure on the contact surfaces without cracking apart. Basically, anything that could take this seal from “pretty good” to “absolutely impossible to penetrate.”
I’ve no experience in this area, so take my words with a big bag of salt
I regularly print PETG planters that are meant to hold a water reservoir. Roughly 1 in 15 will leak off the print bed (certain filaments seem more prone). Over the course of months, a further 1 or 2 will show seepage, evidenced by algae growing at the layer line where the seepage is.
I’m assuming this is an exercise to push the limits of 3D printed parts?
Maybe a TPU gasket or seal? Don’t even have to print this if you can use off-the-shelf ones.
Perhaps some sort of post-processing? Like coating the mating parts in resin or silicone.
First, rule out PLA. PLA has hygroscopic properties, meaning that prolonged exposure to water will cause it to deform and expand, leading to gaps.
So, PETG must be used. Then, the focus shifts to minimizing layer gaps. In my experience, the solution is to increase the temperature and decrease the speed. For example, when I printed a container using the vase mode, even though the walls were very thin, it could hold water without any issues.
I’ve been down the air tight rabbit hole and got models air tight but I had to use a crutch - painting with superglue to seal tiny holes.
Upshot was I was printing with Bambu matte latte brown PLA. I was printing housings for a dry air generator to help dry filament and needed it air tight. Turns out I got best results printing new housings by using filament that had been well dried using a previous housing. (I was refining the design but using them at the same time.) Bootstraps kind of thing. But prints got noticeably tighter when they were printed with dried filament.
I would pressurize the housings and flow water across them to find bubbles and then transitioned to soap bubbles as the housings got tighter. Where I’d see the most leaks were near edges where the extruder would turn around and presumably a little underextrusion was leaving tiny holes.
Printing extra walls and ceilings/floors helped but too many would cause the part to curl a little. Ended up 4 of each. I still had pinholes but the superglue would plug them. I used thick superglue and disposable paint brushes to spread it out. It worked way better than I was hoping.
Last thing I did to try to help seal things up was infill. I started with gyroid just to minimize the knocking you see with rectilinear where the extrusions cross and leave high points. If you want air tight, gyroid is no help at all. It’s totally open and air flows well through it. It could be a strategy for convective self cooling for some applications but not good for air tight.
I went with honeycomb infill. It creates little cells that provide more resistance to air moving across those cells. Unfortunately, the cells are straight shots from floor to ceiling. They did help reduce air moving cell to cell so still helped “seal” even though they don’t truly seal. But they do resist air movement in two dimensions.
Set the line width to be 2x nozzle size (0.4mm nozzle use the 0.8mm line width).
Force the flow rate to be 110%~120% of the original.(Test and use the maximum it can barely prints well)
Thiner layers.
3 walls minimum.
It gives me the airtight prints since I start. So I thought it was a long solved problem. That’s why I focus on the seal.
After reading yours, I do think use the silicon(eg. fish tank glass silicon) to coat a very thin layer around it is a good idea. Or maybe a butane touch quickly blow pass the surface?
