IMHO, the Ox design has a hard enough time just existing at 800x1000mm. It has no business getting ANY bigger. It is a poor design, which has WAY too much flex in any configuration. There are much better alternatives, like the Workbee, but even designs using C-Beam shouldn’t be made any larger than 1000 mm in any direction. The V-Slot profiles just aren’t stiff enough for anything serious in lengths more than 1000 mm.
There have been endless debates on the OB forums about how to strengthen the C-Beam, but nothing has ever been conclusively proven to improve them. It’s just a fact that the OB extrusions are light duty, and you can’t make a silk purse out of a sow’s ear…
If you want a good, stiff design, you have to use much heavier 80/20 or Misumi extrusions that are twice as thick and better designed, or use multiple extrusions to support each axis.
Also, the polycarbonate wheels used in the Ox and other OB designs are not very stiff or stable, and wear out quickly. Linear rails or linear slides are the way to go for large machines. The OB lead screws are also just barely adequate for up to 1000mm, anything larger and they just don’t cut it. And when was the last time you saw a commercial CNC machine with belt drive? NEVER. There is a reason for that.
I have to laugh every time I see someone building a 1500mm or larger Ox based design. It’s ludicrous.
Having said that, in the smaller sizes, they are cost effective and good enough for hobby use, providing you take small bites and don’t push the envelope too hard.