I am making a CNC router from a dremel and 3-5 NEMA 17 steppers. I am really confused on how I can power all those motors. I am using a RAMPS 1.4 with Arduino Mega. I have a 2.4A USB power supply. Is that enough? If not, what is the minimum specs I need to ensure that I don't burn, blow, or under power anything? I am trying to get my hands on a ATX power supply.
I have a 2.4A USB power supply. Is that enough?
Not by a long way, no.
NEMA 17 motors are typically 12V, not 5V, so a USB power supply is not even close.
You will need a decent 12V power supply with a lot of current.
My 3D printer has 3 NEMA 17 motors and uses a 200W 12V power supply. Most of that goes to the motors with only a comparatively small proportion to the hot end.
You need to know the current draw of the motors you are using (note: NEMA 17 defines the physical size, not the electrical characteristics). Sum all those up for all your motors, and that's the absolute minimum you'll need from your power supply. Add some more on top for losses in the motor drivers and to power the Ardiuno.
And I'm not even considering the dremel in any of this...
So yes, an ATX power supply is probably a good choice.