Hi, I'm a beginner in electronic study. I'm recently working on a project to create a rubik's cube solver by using 6 NEMA 17 stepper motors. And my problem is I don't know which power supply to buy for my project. I'm using a arduino mega, 6 A4988 motor driver for each stepper motors and 6 NEMA stepper motors. Any recommendation for suitable power supply to buy?
Urgent 
And kindly send the pic of the power supply and the components requires to connect the power supply with the motors and motor driver.
Thank you.
You need to post a link to the datasheet for your stepper motors so we can know how much power is needed.
12v 0.4 A for each motor
Thanks. That means each motor needs about 12 * 0.4 = 4.8 watts. For 6 motors that will be about 30 watts - I would round up to 45 to be sure.
If you use a 12v power supply it should be capable of providing at least 45 / 12 = 4 amps (approx). If you use a 24v power supply it would need to supply at least 2 amps. The higher voltage will enable the motors to have more torque at higher speeds. IIRC the A4988 can work with 36v - but check the datahsheet.
I have some motors with a similar rating and I power them from an 18v laptop power supply.
Be sure to adjust the current limit on each A4988 to match the 0.4 amps of your motors.
...R
Thanks for the guidance. And one more thing, is capacitor needed in the connection?
The Pololu A4988 web page has lots of useful information. I would have a large capacitor close to the power input terminals of each driver.
...R
If you want maximum speed from your motors go for a higher voltage supply - the power calculation applies the same, so higher voltage means lower current is necessary. The A4988 has a maximum of 35V so you can use it with a 24V supply.