This is my WIP of a linear rail system. It consists of 2 main parts, the shuttle and the rail. The rail has 2 v-grooves that the v-groove bearing of the shuttle fit into. The rail also has a linear rack that will mesh with the gear drive system contained in the shuttle.
The rails are designed to be connected together end-to-end so any length can be accommodated.
The shuttle will also contain a stepper motor propelling itself along the track via a gear.
I believe that with a little more work, I can expand this design into a full fledged 3D system that can be used for 3d printers, laser cutters, light CNC milling,etc...
I'm surprised how well the shuttles v-bearings ride in the track. Overall, it appears to be very stable. I may add some additional bearings between the shuttle and the top of the track to support heavier loads.
I wouldn't recommend printing this because it is a work in progress, but if you insist, print it vertically for the best resolution. You'll also need to print 8 bearing halves for the 4 v-bearings.