Don’t read too much into the term post processing. It means anything done to the part after printing. That covers a lot of ground, it could range from filling in layer lines with powder and resin to sanding and polishing.
So, I’ve been trying to figure out how to print a clear Fresnel lens. I used ExtremeElementz’s IceCube profile, and it was a game-changer. Before that, I was following CNC’s kitchen method, but something was off. Turns out, the secret sauce was to slow down the printing speed and use fine layers, which is exactly what the IceCube profile does.
All I did was polished the cube surfaces the usual way, like you’d polish metal or plastic. I used wet/dry sandpaper and plenty of water, starting with 250 grit and going up to 600 grit. If you’re patient, you can even go to 1500 grit and then buff it. I took a shortcut and used clear polyurethane or acrylic paint for finishing. Acrylic might be better for you because it’s thinner, but you’ll need more layers. The paint I used goes on thick with one layer, but it stays soft for 1-2 weeks until it hardens.
Here’s the stuff I used. It’s pretty good stuff but I wouldn’t use it for something that was a functional part.
https://a.co/d/15h19k5
In the end, I would think you’ll have to experiment between mechanical polishing and chemical coating. You could try out vapor smoothing use Chloroform which allegedly works on PETG but that stuff is way too dangerous in my opinion. I haven’t seen anyone do it on YouTube and all who speak of it won’t mention it by name. It’s kind of weird.
FYI: I am experimenting with other clear filaments. So far PLA failed as did PC which surprised me. None of them showed any hope of optical clarity. I might break down and buy some ABS but I hate that filament and I doubt I could get the temperature high enough to create the optical clarity I’m looking for.