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FOAM CUTTING:

To reach these temperatures -- C/F degrees

  

With .005"dia. Nichrome wire --  (26 ohms /ft.)      volts per ft / amps

 

 With .010"dia. Nichrome wire -- (6.5 ohms / ft)     volts per ft / amps     With .016"dia. Nichrome wire -- (2.571 ohms / ft.) volts per ft / amps With .020"dia. Nichrome wire -- (1.609 ohms / ft.) volts per ft / amps
200 / 392

9.6 / .37

 5.85 / .90 4.13 / 1.61 3.47 / 2.16
400 / 752

15.3 / .59

 9.1 / 1.40 6.36 / 2.48 5.45 / 3.40
600 / 1112 20.8 / .80 12.8 / 1.97 8.72 / 3.40 7.4 / 4.60
700 / 1292 24.7 / .95 14.8 / 2.28 10.2 / 3.95 8.7 / 5.40
                        The above temperature is about right for cutting low density polystyrene foam
800 / 1472 28.8  / 1.08 17.3 / 2.67 11.9 / 4.65 10.2 / 6.35
1000 / 1832 34.8 / 1.34 22.2 / 3.42 15.7 / 6.10 13.3 / 8.30
1100 / 2012 38.5 / 1.48 24.7 / 3.80 17.8 / 6.90 15.1 / 9.40

The above is approximately true for a straight wire in free air.

This is how it works -- On the above chart, you look at the intersection of the wire temperature you want and the wire thickness to find the voltage needed. You then multiply that number by the length of the wire in feet. For instance, if you want to cut foam with a .020" diameter cutting wire, 3 feet long  -- you would need about 27 volts (3 x 8.7) and a power source capable of providing 5.4 amps. This is about 150 watts.

You probably should use a variable transformer -- or a fixed transformer and a separate device to control the voltage (ask an electrician)

Remember -- thin wires need more voltage and thick wires draw more current.