To try and make the frame simple and cheap, it is just copper tube. The bearings are all a 3D printed design I found back on Thingiverse. The Z was to be a very geared down belt Z, but knowing things now, it needs to be self locking. Fun fact, if you want a very tight tolerance tube, a type M copper tube is generally toleranced to +/- 5 thousandths of an inch. With Igus bearings, they fit great with very little slack.