Please critique my CNC machine

I decided to have bt-30 spindle but not clear on the motor

AC- servo or induction motor. The induction motor seem heavy and I have 16 mm ball screw on the Z-axis

The other thing do I need to sink the frame inside concrete to be able to mill mild steel with 8 mm tool

I will appreciate any critiques

Philip


Edit video : obviously the x-axis solid bars are 30 mm in diameter, not 30 meters


https://www.youtube.com/watch?v=zZ1cogS1Is4

I doubt that suspending the spindle assembly on 4 unsupported rods will give you the rigidity you need to mill steel effectively, especially when it's in mid-span, as shown. Maybe if they really were 30 meters thick, though...

Be honest! There is no doubt involved;not only will the unsupported rods move,the lack of bracing on the gantry endplates means they will join the dance too.