How big of a powersupply is requiered for 3d stepper motors

How big of a powersupply is requiered for 3d stepper motors

You can calculate the mechanical advantage of a leadscrew very easily, but first you'll
need to figure out the linear force that you want at cutter, which we cannot guess.

M8 fine would be a very great deal of mechnical advantage, but you would get glacially slow
rapids.

What size is this machine going to be?

BTW standard metric studding is not a precision component, you might need to calibrate
for accuracy and linearity of each such budget 'leadscrew'.  Or source a higher quality
version (stainless studding is worth investigating for this).

For sanity of rapids I'd recommend standard acme leadscrews with a more reasonable pitch (1204, 1003),
and you'll have a much more accurate and linear machine.  Unless its going to be tiny, but you can
get miniature leadscrew, 0802, 0601 I think.

Don't forget stiffness - its not just about forces and torques, you have to check that the mechanical
distortions of the machine under load don't reduce its positional accuracy below what you want.

As for motor supply, you have first to work out what speed you want and thus the supply voltage.  You
might want to check out other drivers that might run cooler or allow a higher supply voltage.

The old PC supply can only give you 12V, which isn't great.  Remember slow rapids are ultra-tedious
in a CNC machine, you spend all your time watching it move from one cut to another.  In a laser-cutter
they use belt-drive, not leadscrew, because you can (no cutting forces).