i wasn't talking about the motors or the price just the simple drive system, and if it does the job then ....

I cant see the point in the printed carriages they will never last under any sort of load and ether the plastic will fail or the surface of the aluminium will deteriorate. I would rather just use something like a cheap set of skateboard bearings and make a arrangement that runs down the groves of the aluminum that way at least the have a larger contact area and the aluminum should not deteriorate

8 x 4 eps blocks are not light but if your frame is not supporting the foam and on a solid floor you can probably get away with a smaller frame I wouldn't even consider anything lighter than 40x40. you need a relatively high tension in the wire to reduce sag and drag if you want straight lines and want any sort of reasonable speed without to much curf. and if you are ever going to do 4 or 5 axis you will need stiffness in the frame to get that, unless you build a complex frame that will likely cost as much.