You should start by testing your circuits true resistance and then calculate to make sure the power supply has enough output voltage and amperage for your circuit and desired temperature.

Go to the Calculations Page for more information on how to calculate these requirements

Make sure that none of your alligator clips are touching each other, as the current can short through the clips rather than going through your NiChrome Wire. Also, ensure that no loose wires are grounding out on a nearby surface.

Determine if you have any in-line short circuits within your device. More often than not, this occurs if you have wired your own DC Connectors or Mono/Phono Connectors. What will happen is when you screw on the outer casing, it may squeeze your cables together and making your two leads touch each other. This will cause the power to bypass your NiChrome Wire, and loop through the short circuit rather than power your Hot Wire Foam Cutting Device.

Start out by removing the NiChrome wire from either side of its attachments, by unscrewing your wing nuts and remove the spring and figure of 8 attachments. Then attach the positive and neutral leads from your voltmeter to either side, where you would have otherwise connected your NiChrome Wire.

Turn on your power supply and depress your switch, if you have one. Using your voltmeter you should be able to assess both DC Voltage and Amperage - Use the 200m/10a Amperage setting, and the 20 DC Voltage setting.

If your voltmeter does not register any voltage, then you have a short circuit in your Hot Wire Foam Cutting Device. Hunt it down, it will probably be at the connection between the device and power supply. But if you had not connected your end cap electrical components correctly, one wire may have slipped from its attachment.

This problem is a bit more tricky to diagnose and to fix.

Please visit the Power Supply Mechanics page for more information on power supply functionality.

With this model, we are assuming that you purchased a variable voltage power supply. But you can easily extrapolate this information for solid state power supplies as well.

With each length of NiChrome Wire it has a defined resistance and a required current/amperage to heat the wire. Your voltage is what provides the electrical force to push the current through your NiChrome Wire.

Send me your problems, and I will try to post a resolution!


Purchase a Voltmeter/Multimeter from your local electrical supply or hardware store.

Using this test equipment will help you find any short circuits in your cutting equipment or make sure that your power supply is providing the estimated electrical power.

Below I have outlined a few scenarios which you may come across with your cutting tools.

“My power supply is on,

but my wire wont heat up!”

“My power supply is on, there are no tested shorts, 

but my power supply clips out before my wire can heat up.”

To increase the resistance of your circuit you can attempt to find an actual electrical resistor, or try a smaller diameter wire in series with your NiChrome Wire. Resistors are usually VERY cheap, and you could get a bunch of different resistances and try them out.

Check out the Resistor Section for more information

For instance,

    6” of 26 gauge NiCr C has a resistance of  1.335 ohms

    To heat 26 gauge NiCr C to 600°F / 316°C requires  2.1 amps

Ohms Law States

Current = Voltage / Resistance


Voltage = Current x Resistance

Voltage = 2.1 x 1.335

Voltage = 2.8

Your power supply will need to be turned to 2.8 volts in order to heat your wire.

When resistance is kept constant, and you increase voltage, you will therefore increase current. But all power supplies are only rated for a certain output amperage. When you increase the output current beyond its rated output, you may damage the internal components, it may heat up & short out, or activate the power supply’s Over Current Protection (OCP).

One type of OCP is that some power supplies will clip out and stop any output wattage from the power supply, in order to protect the internal components.

A unit I had one time, when it was attached to my cutting device would clip out around 11-12 volts at 2 amps. My cutting unit was set up with 26AWG NiCh C with a resistance of 2.67ohms/foot. The length was 15 inches which should calculate to 3.3 ohms (2.67 x 1.25 feet) but with the other metal components it measured out at 4.4 ohms (as tested by my multimeter). To heat to 600°F, I needed 2 amps, which calculates only 8.8-9.0 volts from my power supply. Since my power supply clipped out at 11-12 volts, I never actually had to approach the threshold of my power supply to heat my cutting device.

But what if you want to increase the voltage beyond your calculated value?  Remember, it is the amperage that heats the circuit, not the voltage. That said, as you increase the voltage you will increase the amperage. Think about ohms law, since resistance is constant, when voltage increases, so does amperage. With some power supplies you can increase the voltage a bit above your calculated value and draw more current from your power supply than it is rated, AND get away with it. Just be careful and monitor your power supply heat to the touch.

For the most part, if you measured your resistance and calculated your voltage correctly, you shouldn’t have to increase beyond your calculated values.

Taking our previous example,

    6” of 26 gauge NiCr C has a resistance of  1.335 ohms

    To heat 26 gauge NiCr C to 600°F / 316°C requires  2.1 amps

    The power supply needs to be turned to  2.8 volts

Extra voltage = 5 volts - 2.8 volts

Extra voltage = 2.2 volts

Ohms Law States

Current = Voltage / Resistance


Voltage = Current x Resistance


Resistance = Voltage / Current

Resistance = 2.2 / 2.1

= 1.05 ohms

You need to add approximately 1 ohm   to your circuit

These two problems are actually fixed the same exact way.. increase your circuit resistance.

If your power supply only goes as low as 5 volts or if you have a power supply that only supplies 5 volts, then you need to increase the over all circuit resistance in order to be able to compensate for the increase in voltage.

Remember that the power supply provides a constant output voltage.  Therefore to account for the extra voltage but still keep the current the same, you need to add more resistance.


“My variable voltage power supply only goes as low as a set voltage, what do I do?”

“I have a solid state power supply, how do I make it fit my cutter..”