"Tough" resins good enough for little boxes, toy clock gears, etc?
I like my MK3S a lot but now considering the SL1 for some smaller parts with more detail or precision. I've heard SL1 parts are very brittle, but I see tough resins and flexible resins available. Are they anything like the strength of PLA for small parts? I wouldn't expect the parts to hold up to mechanical wear or big loads, but I'd like them to not be a lot more fragile than a filament printed part. Think in terms of a small box with a lid, sized to hold say some guitar picks, or a case you'd put wireless earpods inside. Looking at the strength properties Prusa publishes, it seems like the material might be OK. It seems to be roughly the same strength as PLA.
Thanks for any advice from someone with some experience in making some sort of mechanical parts, as opposed to mostly artistic parts and models.
RE: "Tough" resins good enough for little boxes, toy clock gears, etc?
First of all, do not think of the SL1 in terms of your MK3S. I did and I regret it. It's a nice machine, but the support is simply not there (either from Prusa or the community) and I have (unfortunately) needed far too much of it (bad UV board and LCD out of the box, leaking tanks due to their design, and now my LCD is dead with only 161 hours on it). When it works it produces great prints, but I should have been able to burn through that 161 hours in a bit over a week rather than 3 months it was first delivered. There are some nice features (PrusaSlicer, tilting tank, resin sensor, etc..), but I'm not sure any of them are "killer" features over what you get in a much cheaper printer that produces the same or better (I'd recommend a 4k mono printer) quality.
As far as the resin, you are not limited to just using Prusa's offerings. Any resin that cures at the 405nm wavelength will work. They even include a resin calibration function (probably the closest thing to a "killer" feature in my book) to help you determine the best exposure settings to use.
Basic resins are brittle, but they won't crumble by looking at them funny. For your box examples a standard resin should probably work just fine, though if you were to drop it it would likely shatter. Depending on the pressure they are facing gears may or may not work.
For things that need more resiliency (e.g. will see torque or pressure) you can move up to "tough" or "abs like" resins which are less brittle. You can also mix a flexible resin with another resin as well to help make it less brittle.
RE: "Tough" resins good enough for little boxes, toy clock gears, etc?
I've compressed Monocure3D Tuf resin to over 10 tons (metric) in my press, where the object is at least 20mm z height, and 32mm in x & y. This is compressive strength, but there are also tensile and impact strengths to consider. See https://monocure3d.com.au/product-category/rapid-tuff-resin/?v=322b26af01d5
Surprisingly, these prints are strong enough to form 2mm steel! (but then so is PETG). Refer 3D Printed Sheet Metal Forming - YouTube
This Tuf resin is not quite as strong as PETG, so I suggest you try PETG, before springing for an MSLA printer like the SL1. MSLA is more work and not as environmentally friendly as your MK3S. On the other hand MSLA prints are isotropic (same strength in all directions), whereas FDM is anisotropic (different strength in different directions), and also MSLA can get finer detail. The detail is amazing, but it takes a lot of trial and error to get the best prints. I'm finding that I'm getting voids in my prints, which look like a problem in software in the SL1, or my LCD needs replacing. Prusa Support can't give me a conclusive answer.
I agree with gnat. If I was to buy another MSLA printer I'd be tempted by one with a larger 2K or 4K mono screen, but for my use case, an FDM printer like you have is probably the better choice.