First steel diy CNC router build

[ivars211]

Thanks Jonathan for your response. The question now is, what's the optimum 'aspect ratio'?
For Y axis - distance between rails 700mm, distance between rail blocks 250mm, so that's aspect ratio of 0.3571
For X axis - distance between rails 320mm, distance between rail blocks 200mm, so that's aspect ratio of 0.625
For Z axis - distance between rails 120mm, distance between rail blocks 200mm, so that's aspect ratio of 1.667

I might consider going double ballscrew design, but that's also increase in cost. I have also read that there is a possibility of racking and damaging machine, if one of the steppers stops while other one is still going. So is the gain really noticeable in relatively small machine? Isn't steel frame rigid enough to prevent racking?