Quote Originally Posted by Davek0974 View Post
Looking at the dimensions more, i can only repeat earlier comments - this is not a machine for what is called "plates and skates" motion - ball bearings running on steel plates. It works reasonably for small stuff - my first plasma cutter was plate & skate but it jammed a lot due to crud on the plates and it was only 650x650mm, over a length of 3000mm the motion will not track square or level.

This would be a big machine, heavy and expensive I feel, it will need to be if it is to do any sort of work at all. If it were me building big, I would be looking at ball screws, 25mm linear rails, 750W servo motors at least, and a heavy steel frame. I would not even go with the round supported rail at this size. Just my thoughts of course. :)
I'm planning an 8*4 machine next for wood only and I was going to use SBR25 and I'm sure it would be very nice but the price of HIWIN 25mm from cnc4you (About 50% more) means I'll just go with 25mm Hiwin on X&Y and 20mm for the Z.

I costed it at ~£1500 delivered from cnc4you for
2*2.7m HIWIN
2*1.6m HIWIN
2 * 2005 2.6m ballscrews with fittings
1* 2005 1.6m ballscrew with fittings

but I think I would want to fit a minimum 2510 (Or 2520) ballscrew for the gantry and R&P for the long axis (So I can do a dual gantry, independent drive).

R&P gets a bad rap but I've seen some very accurate setups out there certainly on par with the C7 ballscrews I would buy and with ballscrew mapping I'm sure well within any tolerances I would ever need with such a machine.