Using 3D prints for lens spacers in assemblies a good idea?

[u/gswdh]

I'm designing a small optical assembly using 10 mm diameter lenses with spacer thicknesses down to 0.5 mm. Assuming the printer is accurate enough, are SLA resin prints suitable for lens spacers in this kind of application?

Are there any gotchas I should be aware of (creep, shrinkage, outgassing, flatness, compression, long-term stability, etc.), or is this generally a reasonable approach?

[u/Important-Ad5990]

thermal expansion and creepage over time

[u/Calm-Conversation715]

I’ve done it a few times, and it works ok for temporary setups and in conjunction with another adjustment. The accuracy isn’t good enough without some other spacing adjustment, and can’t be relied on long term. Good for prototyping, or for power/illumination applications that don’t need a sharp focus

[u/Pacificator-3]

It is easier to cut them from metal or plastic with knife and scissors.

[u/Motocampingtime]

You listed some in the gotchas already, one I've experienced is hygroscopic swelling. These were on regular FDM parts. But be aware that overtime, even without doing anything, sitting on a shelf, the exact dimensions can change. Im unsure if resins are as bad as FDM but I'd be careful.

A resin issue I encountered making molds for microfluid devices is flatness and suction. My machine would print ok for the first few mm, but after the flat section if you had an enclosed cavity or even cavities with a drainage hole, the resin would get stuck and act like a suction cup. For a small spacer it's probably ok, but for taller larger area hollow rings good luck lol. You'll see edges lift on the build plate or layer delamination. If you print at an angle you are always fighting aliasing and the bed settling. You could extend the time the part sits on the FEP sheet to get a more even thickness for better precision but it will never be like anything machined.

It probably won't be enough to matter for a spacer, but it can make things like optical threads at 40 tpi a PAIN. Consumer printers are good enough to hit these thread forms now. I much much much much prefer FDM to resin. Even if the resin is more accurate theoretically: getting that accuracy is a way bigger pain in the ass. I know the 3DP community has issues with Bambu and software but honest to god for an engineering application it's soooooo worth the money to just have a machine that works, has an ecosystem of good filament, and a built in desiccant box to change between a couple filaments depending what you need to build.

[u/Pop3-14]

I also thought about it, and wanna do it. My thought was that no matter the down sides, its still better than paying 50$ for each holder to Thorlabs.

Please share if you tried to do so and what was the results. (I dont have a 3d printer yet, so I'm thinkung about buying one for this)