Sorry for first post being a product request, I don’t really use forums much anymore. Anyway:
There are such things as optical transmissive linear encoders with a high resolution that don’t cost $50 just for the strip. We know this because they’ve been used in some models of inkjet printer for years and while those are loss-leaders they aren’t that costly to make. I’m thinking if there were a good source for these parts there could be some much better CNC designs than the current dependance on steppers and dead-reckoning that seems to dominate presently. Sure if I was going to design one on my own I could easily track down a used Epson or two with them and reverse-engineer the encoders but that would require designing yet another FDM printer design from scratch and honestly the number out there is starting to look stupid. If these encoders could be sourced they could be incorporated into an actual reproducible design.