# THC Voltage Variating 20+ volts

I am in the process of diagnosing what I believe to be a THC issue, I ran a few straight line cuts back to back & just monitored what was going on with THC while it was cutting.

I was cutting 14ga mild steel, using Hypertherm 45a fine cut cartridge, using Smart voltage

My first cut I saw an average of 64 Volts
My second cut I saw an average of 69.8 Volts
My third cut I saw an average of 82.3 Volts

When I look in the Hypertherm book it says best volts for 14ga is 88 Volts… with my first cut at 64 Volts that’s a 24 Volt difference… Is that normal or is there something wrong here? I have done multiple THC tests & they’ve all passed.

try writing in your nominal voltage.

I think i use 78 volts with finecut on the powermax 85 for 14 ga.

I normally use straight book values

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I’m going to start using nominal and see how it goes, I’ve been using smart voltage ever since I got the table up and running but I noticed this big difference in voltage when doing these tests & wasn’t sure if that was a sign of something else that I need to troubleshoot.

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worn consumables and cut height can affect this .

also work “ground” clamp location

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@backwoodsmetalworks i always use nominal voltage settings…it will need to be changed based on metal thickness but i find it way more consistent than smart voltage.

The lower voltage could be from the material spring back. If the material springs back more than the set value, the cut height will be lower by the amount the material springs back or is warped.

The way the smart voltage works is that it takes voltage readings during the first .25" of the cut and then the THC will move the Torch up or down to maintain that voltage.

For that reason, if the material springs back or is warped, the actual distance between the torch and material is less than the set cut height. That will result in a lower voltage than expected and the THC will maintain that voltage, because it thinks the voltage samples were taken at the correct height.

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I get what you’re saying… but wouldn’t the material be more prone to spring back on the 3rd cut rather than the first? My first straight line cut, the one with the lowest voltage was when the material was near or close to room temp, you would think after 2 cuts & all that extra heat that on the 3rd cut the material would be prone to have the most spring back of them all.