Project Da-Ta CNC mill

[Da-Ta CNC]

Hello everyone.

Here is our second CNC project.
I would like your opinions, pros and cons, just for start, this model is not finished yet.
We will be using 20 and 25mm guides. Dimensions of working table is 500x500mm.
Our question is what kind of spindle should we buy? Goal is to mill steel (hopefully).
Roough 3D model:

26837

[Da-Ta CNC]

ok no response on spinder power ...

Maybe someone have any ideas how to adjust Z axis (vertical) to be 100% perpendicular to the table? If I weld it to the frame that wont be possible.

[routercnc]

My thoughts on spindle for milling steel are you needs lots of torque and not so much speed. Popular ways to do this are a pulley driven spindle rather than direct drive. Maybe 1kW or so motor into a 2 speed pulley arrangement to drop the speed and increase torque.

3 phase motor into VFD to give infinitely variable speed range would work.
Can also be a servo with encoder if you need rotary position for rigid tapping.
There are also DC motors using variable speed control. I prefer VFD control over these as the inverters give lots of control options and possibly more torque (?)

Z axis alignment to bed is usually done by making the whole column a single unit welded onto a flange. This is then bolted onto a receiving flange on the bed which allows shimming or you can go for epoxy compounds but these are pricy !

[Da-Ta CNC]

thank you for your answer, spindle is realy better to be pulley, more torque, I agree

What about bearings for ball screw? Does they need to be high precision? Does they effect accuracity of the machine?

And for clutch? What do you recomend?
https://image.made-in-china.com/202f0j00JPsYckdEZaqD/Clamp-Screw-Rigid-Coupling-CNC-Stepper-Motor-Shaft-Coupling.jpg
something like this?