Quote Originally Posted by NordicCnc View Post
The surface finish achieved in this video, I would be more than happy with:
Thought you said wanted a good surface finish.!!. . . . Any decently built machine will give you that finish.

Also:
If you go with 30mm rails and 25 or 32mm ball-screws then you can forget 180w or 400w servos. The extra inertia will freak a 400w servo motor when trying to stop 25mm screws from 3000rpm that are attached to a reasonably heavy Gantry which is sat on heavy bearings with a heavy ATC spindle hanging off it.

The best machines are those that have the right balance of power and weight which means getting the design and components matched. The choices you are looking at now will give you a very unbalanced machine.!

20mm screws and rails are more than enough for a machine this size. Regards the screw size and whip etc then forget whip calculators because they can't and don't account for the whole machine.
If you want proof if 20mm won't whip at 15mtr/min then just ask anyone who's using them on similar sized machine.! . . . . I've built dozens and trust me they don't if properly aligned and with correct end bearings. However, I've told you how to eliminate any chance of whip and still get the speed you require.

Also on that note, you have to factor in the Servos and the extra resolution and power they offer over steppers. This means you can use higher pitch screws and still end up with good resolution compared to steppers. Use this along with applying a ratio and the screw speed can be lowered greatly.

Regards the weight then I think you must have got something wrong because a machine this size will easily weigh more than 200kg, even 300Kg by time it's all finished.