Thank you for sharing your outstanding build, Sam. First-rate documentation and camera work. In Video #2 @ 8:53 you mention you will explain all parts in more detail. However, components are never mentioned again and there is no Bill of Materials. Is there any way to find out more about the parts in your system?
A fundamental way of judging the quality of any x-y system is to view or measure the cross-over of 2 axis (i.e., when a motor reverses direction). This occurs at 4 positions when creating a circle. From what I can see in video 8, the stainless circles are perfect as well as the various rings you routed in wood. This would indicate very high quality system design, and components and software with little to no backlash . . . so a few questions: :-)
1.) You mentioned MasterCam . . . did you use that software?
2.) You mentioned the racks may not be as good as you would like. How do you compensate for backlash of the racks? Does your software do backlash compensation?
3.) Considering cost vs. benefit would you still use racks, or recirculating ball screws, or?