What power supply?

I'm building RichRPs 3dr but 1 mtr high with a kossel 220mm heat bed with wantai 0.9 deg steppers and a Rumba control board.
I have various atx psu's floating about that I can use up to 640 watts.
What kind of power will I need and would it be worth going 24 volts with an ssr for the heatbed or will the 12v heat it up in a couple of mins?
I'm looking at using abs as well as some of the exotics and pla, but mainly pla.

If you want to get good speeds with 0.9deg motors on a delta, you will need to use 24V. You will also need 32-bit electronics to achieve a sufficient step rate.

See [duet3d.com], [duet3d.com] and [duet3d.com] for guidance. Those pages were written for the Duet series, so if using another control board you will need to substitute the appropriate bed heater current rating.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

So, ignoring the Duet board for the mo, if I have a possible 5 steppers at 2.4 amps, up to 3x40 watt cartridge heaters or whatever the 24v equivalent is and a kossel 220mm 12 volt alu heat bed running on 24 volts, would a 350 watt 24v psu be sufficent?

Sorry for these questions but I'm more nuts and bolts than working out power requirements.

The 3rd page that I linked to tells you how to work it out.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].