Quote Originally Posted by Richard View Post
Is there an optimal spacing for the x axis carriages - assuming that loss of x travel is acceptable to get a more rigid gantry?

Does having the carriages further apart add much benefit?

I guess this apples to all axis?

So for hiwin 20mm carriages, set with a gap between the seals of say 40mm, the total width of both carriages comes out at something like 200mm, so to have a working x of 1500mm, you need another 200mm of rail and bed.

This dimension really sets a lot of the overall dimensions of the machine...
Don't think there is an optimal, like you note, you want them as far apart as possible with the least amount of compromise on axis travel, if you get down into the science, it's just not possible to mount the bearings at distances apart that the numbers suggest.

I think an absolute minimum distance the bearings should be spaced apart, is whatever the distance is between the rails, lets say 250mm.

Designing this type of cnc machine is a constant search for equilibrium, great fun though a!