Monday, October 20, 2025
Shielding Gas Curing Test
The CO2 container helped, but did not preserve the fine detail - that stayed gooey. Not good enough, but will repeat the experiment in case it was a fluke and give more than 4 minutes curing time. Yes, that's short for curing normal prints but its not as if the UV has to penetrate very deeply.
Perhaps there is already significant oxygen dissolved in the resin from exposure to air during deposition? The larger blobs were also distinctly wet underneath, but not as bad as earlier attempts. So I put the sample in the air fryer at 90C for 15 mins. Still not set, let's give it another hour...
Maybe some kind of cover to avoid flying fried chicken particles might be a good idea next time. Anyway, some more resin cured, and there are small chunks of cured resin in the print, but the fine details are not preserved.
So what thickness of printer resin do I need before it'll cure? Well, I have the blobs, so I broke one apart at the thinnest identifiable solid area and set a fragment of it on edge:
This also shows my limits for manual manipulation. The answer appears to be about 25μm. As I'm depositing dots smaller than 10μm, no wonder I'm having poor results. It also means that unmodified printer resin is not going to be useful with fine probes, and any objects I deposit need that as their minimum thickness. Damn. Something else to test as well.
There are additives that I can use, which are in common use in things like UV nail varnish and fibreglass resin hardener. Plenty of things to try out. I might try putting a few dots down, leaving them exposed to air for increasing intervals, cover them with gold leaf to exclude air and try hardening that.
Mechanically, the resin is relatively inflexible. From just poking at it with a probe though it feels like I could make some kind of flexure out of it. No idea how it'll stand up to repeated stressing. Also there are more flexible UV resins available for DLP printers, and standard/flexible resins can be blended to get the desired rigidity.
I think I may have to lay hold of some "No Wipe" UV nail varnish. That has an oxygen inhibitor in it so that a thin layer can cure in air - and I can buy 15ml quantities. Hmm, I wonder if I can get some in translucent colours to make imaging easier? Plus I can do up my nails...
