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SLA Curta

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I stumbled upon this build while looking for complicated mechanisms to test out the capabilities of the FormLabs Form 2 in making precision mechanical components/systems. I think there is little question that a Curta fits that build.

However I note that this build is based around using Fused Filament prints. I'm wondering, for those who are already familiar with the 3d geometry and the development of these cad models, what further consideration should be taken in attempting to print the components using an SLA printer. Should the extra "stock on" of the 3d models be reduced, or eliminated? As I understand it the interfacing components in the models are designed to have interference, with the intent of manually grinding the surfaces to match. I'm wondering if it is practical to reduce this stock on.

Additionally, what would be the bottle neck to scaling the build down? Would a 2:1 assembly be practical? Obviously all the non-printed components such as hardware, bearings, springs, etc would have to be re-assessed and new components sized. I imagine the entire assembly would need to be redesigned as opposed to simply scaling the solids and hitting the go button. My question is, would such a thing be practical? What trial components/fits could one start with to substantiate that the redesign of the assembly to a different scale would not be a wasted effort?

Any and all feedback is welcome. Thank you.

I have a DLP Printer and start to understand the curta. I have seen there are a few collisions in the model and I start to design a new CAD-model. There is a lot to improve to have better prints on DLP/SLA, because the print methods are to much different. But this will take time.

In additon, do you happen to have the original CAD models the stl files were generated from published some where? I would like to build a digital assembly in a CAD package to play with and look at alternative options for scaling and hardware selection. I could work backwards from the stl files, but I thought I'd ask if you already have such a digital assembly available.


Wow, I can't believe I missed this thread. I'm sorry, I try to respond to everyone.

I think a 2:1 build might be practical for an SLA printer. I've wanted to try it out, but have had a lot of other things to spend time and money on. Yes, some of the parts would need to be tweaked for tolerances and all of the tolerances would need to be adjusted for 2:1 scale instead of 3:1 scale.

The source CAD data is in OnShape: 3:1 FDM scale, and 1:1 scale at nominal dimensions (no tolerances)

I wanted to be able to scale up and down the models easily, but I realized that the tolerances wouldn't scale the same as the rest of the model. Many of the tolerances are added into the sketches as expressions (unfortunately OnShape doesn't or didn't at the time support external formulas that could be applied across the workspace). Hopefully the work isn't too hard to reduce it down to 2:1.

I have an SLA printer and found that I could fit the largest parts at 40% (or essentially 1.2:1). Of course, the hardware would have to be scaled as noted.

I have used a Go-NoGo test for the AnyCubic Photon so I have a good handle on the tolerances for the resins I would use.