During the robotics season we 3D printed a pulley. It didn't wind up failing on us, but plastic always makes me a little nervous. So on April 28, 2024, I set out to cast it in aluminum, using the printed plastic part itself as the pattern (lost-PLA casting). It worked.
Here's the rough casting on the left, sprue tree and all, next to the clear 3D-printed pulley with the same sprue on the right.
You can see the layer lines in the result. Note the bumps on the casting: I clearly didn't degas the mold enough, and air leaked out from inside the print. Those would file off easily enough.
And the texture from the print plate came through, including the print lines. Pretty good detail!
We did not wind up using the pulley, but it was still a good experiment.