Taking this into a different discussion as per request. Let me start by saying that I am not any kind of mechanical engineer. I studied computer science, so there’s plenty I don’t know about building things. Just trying to have a dialogue, and hopefully learn stuff.
True, but don’t belts stretch as well? There are always going to be sources of inaccuracy in a CNC. There’s no such thing as a truly rigid body, nothing is perfect. However, I know there are R&P based machines out there that do amazing stuff. One example is Joe’s Hybrid CNC: