I am somewhat familiar with cnc themed devices, delta 3d printer, large laser engraver, draw bot, sadly all from China. I think the motion part is fairly straight forward, my issues have all been with the bit that actually does things, that and my customer support being Google (aliexpress sourced kits).
3d Delta printer (nozzle clogged, locked down firmware so no starting point for mods, one sentence instructions in bad English, control board with the iffy Chinese usb serial controller, random disconnects).
Laser Engraver (power supply under powered, causes endless missed steps with the two stepper motors per axis design, laser turned out to be more of a commodity to be replaced. Same Chinese usb controller, random stops, software OK but underwhelming, tried a few.)
Drawbot (the part that lifts and lowers the pen is a commodity actuator, buy bags of replacements, Chinese usb serial bit, so ditto.)
3D Delta Printer (I was able to create a few tiny things, I think by accident more than anything, motion of the machine was very cool, more work to be done than I had time for, random controller board with no support, would have to reverse engineer somehow or replace and guess settings.)
Laser Engraver (After creating another power supply I got some good use out of it, burnt a lot of wood, caught styrofoam on fire, put Looney tunes characters on a few t-shirts.)
DrawBot (still working, well have to replace a rubber band, but lots of drawings, used as a plaform for experimenting with the code for lasergrbl and mutile passes to create shading / multi colour.)
One lesson learned, buy a open controller board with a working data connection (or headless or pi based), and stay away from China unless it is something that is entirely self contained or very simple that needs zero support.
So now I am looking into using a router of some kind, and the most appealing kit to me is the lowrider 2. A beginner yes, but some idea of what is involved.
First concern, specs of the metal tubing, I am in North America (Canada) so 25.4 or 1" and 16 gauge / 0.0695 mm walls.
First attempt at searching was this:
Not sure what gauge that is though.