Fully opaque resin for film photography

Hi, I’d like to print reusable film cartridges for things like Super8 or 110 cameras, and these cartridges need to be fully opaque once they’re printed, with a minimum cross section of about 1mm or so for the thinnest parts. I’ve done some preliminary work with an FDM printer to prototype and prove it’s possible, but resin printing of course gives a much nicer end product. I guess this is probably impossible given that the resin needs to allow UV light through in order to cure, but it’s not something I’m very knowledgeable about, so I’m reaching out for advice. Thanks in advance.

UV only cures the surface, it doesn’t go through the parts (unless they’re clear resins).

I’ve done lots of parts with thin walls and features (0.5mm) and I would call these resins opaque:

  • Black
  • Model
  • Grey
  • Grey Pro
  • Tough 2000

Please note that to my eyes they’re opaque in thin walls / features. I never added a light focused directly behind them but it doesn’t show any kind of transparency.

For example, Rigid 4000 is not fully opaque in thin areas even though it’s a rigid resin. Even a 3mm wall shows a small silhouette of any object directly next to the wall which means that light goes through even if just a bit. I have to go 4 to 5mm thick to make it opaque.

With the possible exception of Black, I don’t think any of the colored resins are truly opaque. And with thin enough walls, not even Black. “Translucent” is the term I’d use to describe them. Put a bright enough light behind a print and some will get through, particularly with thinner walls.

UV does penetrate the resins deeper than just the surface. How deep is a function of the resin and how much UV light there is. This is the whole point of post-curing a print, and why it takes time to accomplish that (if it was just the surface you were curing, a UV flash bulb would do it). The printed resin is in what FL calls a “green” state (still soft and pliable). If UV didn’t penetrate (because the resin is truly opaque or because the UV light source isn’t bright enough), you’d never be able to fully cure a print and the resin would never realize it’s targeted physical characteristics (strength).

If you want your prints to be truly opaque (or “opaque enough”), you will probably have to paint them.

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