I want to make a CNC machine that uses 5 NEMA 17 rated for 2A and a RAMPS 1.4 to control it all. I have a power supply that can deliver 1.5A at 12V. Is it enough? I am worried that when all 5 motors are under load, the amperage will get distributed and there will be very low amperage per motor.
Figuring out your current needs is simply a matter of adding everything up. If you have 5 2 amp motors, you'll need 5 x 2, or 10 amps just to drive the motors.
You should probably have at least 20% extra capacity, so I'd suggest having a 12V power supply that can put out at least 12A.
15A would be better.
The stiffer your power supply the less it will "bobble" as the load varies.