The wire is just a resistor: you set heat by controlling the current through it. Use a separate low-voltage, high-current DC supply (commonly 12–36 V, several amps) sized to your wire length and gauge, and dial the heat with either an adjustable supply, a PWM MOSFET module, or a series resistor.
Rule of thumb: longer/thicker wire needs more power. Start low and raise until the wire just glows faintly in a dim room and slices foam at your feed speed without dragging. Too cold = the wire pushes and tears; too hot = a wide, melted, droopy kerf. Never run mains voltage through the wire, and fuse the supply.
Rule of thumb: longer/thicker wire needs more power. Start low and raise until the wire just glows faintly in a dim room and slices foam at your feed speed without dragging. Too cold = the wire pushes and tears; too hot = a wide, melted, droopy kerf. Never run mains voltage through the wire, and fuse the supply.