3d printed threads and snap connectors are nice, but M3 bolts and nuts are more robust and look dope. They also make the model easier todesign print, since you don’t have to worry about tolerances as much.
STEP/STL and instructions available here: www.printables.com/model/548770-master-spool
Problem is extrusion consistency. If you want them to be affordable, you need to sacrifice precision. We print with 0.4 mm nozzles, and any inconsistency will show up. Plus the color is less uniform. There are already pellet extruders. Cnc kitchen tested one a while back.