It's been done, but you run into problems immediately. For one the tolerances on 3D printing are not as tight as you'd like for a device like a Curta, which is

It's been done, but you run into problems immediately. For one the tolerances on 3D printing are not as tight as you'd like for a device like a Curta, which is why the example I'm aware of printed a replica at a much larger scale. Additionally, 3D printed plastics are typically not very strong, and they change shape over time. This means that the usable lifetime of a 3D printed Curta is typically not very high.