You may also want to get in touch with the Phlatboyz as well. I think that’s their name… You’ll have to google them.
Working on the Printrbot Pro this week that has a modular core xy and a z on each side in the middle all mounted to an extruded aluminum cube/box. We’re building it to scale up big. All that said, there is always a practical limit. Leveling the bed and keeping a span that size flat will be tough. A 1 meter cube, or something close, will be our next step. Get ready for print times measured in days and the need for really big filament rolls. Our will be a triple extruder, so you could utilize 3 spools without the need to change spools. Our experiment will be an experiment, but we would be open to custom bot kits made to order… They won’t be cheap but we could make huge bots for under $3000.
Brook Drumm
Printrbot
@Javed_Khan a custom-made XXL version of our stock #DeltaTower features a machine height of 2,2m. The build volume is about 80cm in diameter + 1,2m of height. So not really what you’re looking for. Larger could be built I guess… but then again: You need a special extrusion system otherwise you can’t get it filled in a reasonable time. You should talk to the guys of http://www.dusarchitects.dds.nl/kamermaker/wordpress/
Thanks @Jason_Ray for referring to us 
// Greetings, @Florian_Horsch_flouS
@Tim_Rastall , the Joes 4’x4’ CNC at my lab can travel 4 feet in roughly 5 seconds. But we’re using some amazing servo motors, 8mm/turn leadscrew, and some gearing. Back when we were using Nema 23 steppers, there’s no way we were able to achieve those speeds. But for a machine this size, you really want to go all out and use servo motors + gecko drives. You don’t want a multi-week print failing 1/2 way through because of some missed steps.
@ThantiK . Very interesting, that’s about 250mm/s by my reconing. Would you trust those travel speeds for printing? You’d also need a crazy fast extruder I imagine. Also also, your lab sounds awesome 