I am wondering why there is no open framework for laser printing.

There are a few parts that would have to be made out of sheet metal. The sides could be stamped for the same pattern. You then need a back and a cross section. One could theoretically make them from ABS, but ABS gets brittle with heat and the sides will shatter.

One side of the printer is dedicated to running an ARM SOC. I’m not sure if the Arduino is up to the task, but it will need to control 3 motors, initiate a heating sequence, start a rasterizing laser, interpret a print job, communicate over network and USB, and monitor a bunch of sensors.

The hardest parts will be obtaining print cartridges, rollers, and fusers. Designing a standard to run off a certain vendor’s hardware will be a pile of issues, and nobody will just start manufacturing hardware for a handful of hobbyist printers.

Everything else is 3d printing, springs, and screws.