10 Gauge Stainless and THC

I have sent the following question to Langmuir Support but thought some of you folks on the forum have already solved this so figured I post it and see:

I’m planning on cutting some 10 gage stainless using fine cut parameters on Hypertherm 45XP. Looking at the cut charts for Stainless it has the torch cut distance as 0.02" which is significantly different than the 0.06" for mild steel. Additionally the pierce distance is 0.08 for stainless compared to the .15" for mild steel. I can set these parameters in Fusion 360 CAM but am wondering how the THC will know Im cutting stainless vs Mild steel and use the recommended height as provided by the cut charts. Should I disable THC for these cuts or do you have a better solution. thx Dan

The machine doesn’t know what you’re cutting, it will do whatever you tell it.

If you tell the machine what pierce height and cut height to use, it will pierce and cut from those heights.

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Got a reply from support as follows:

Hypertherm cut charts typically specify a target voltage to set instead of standoff distance in the case that THC is being used. You will want to set the target voltage specified in the cut chart as the nominal voltage in the FireControl THC control panel. From there, the THC system will make standoff distance adjustments to maintain the nominal voltage setting.


I got to admit I’ve never messed with setting a nominal voltage but have always just set the pierce and cut heights in the post process page yet I had noticed that for steel even though I selected a cut height of 0.06 for steel when I paused a cut the cut height was quite a bit greater than 0.06 so I knew THC was making some kind of change to the parameters I set. With this new info from support I now look at the cut charts and while the pierce and cut heights are the same from 16 GA to 1/2" the voltages are unique for each!!!

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Yeah, I’ve never set the voltage on anything I’ve cut. I’ve just let the THC and smart voltage do it’s thing.

My voltage readings from firecontrol have always been in the neighborhood of the book specs. Maybe it’s time to experiment a bit and see if I can see a difference in the cut by giving it a target voltage.

So reading the links, it states that the voltage increases in small intricate cuts so firecontrol disables THC to avoid the torch driving down to compensate. So naturally with slower cutting on thicker materials you get the higher voltage.

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I fear this could turn into a science experiment! :joy: but the more I read the more questions I raise in my feeble mind! For instance, the IHS is supposed to sense the surface of the target plate and then adjust to the correct pierce height and then after pierce delay lower the torch to the cut heigh. The way I read it once the pierce is done and the torch has moved to the cut height and starts cutting and has moved the offset distance (default is .25”) the THC system begins sampling the arc voltage. When it has the set number of samples (default is 50) that becomes the current nominal voltage for that cut loop and the THC will then adjust the torch height if that voltage varies more than the tolerance value (default is 1.5V)

Thus setting the pierce and cut height should get you in the ball park. But then why is my cut height not the 0.06” that the cut charts call for? I have set up a cut and paused the program the instant it starts a pierce and sure enough it measures 0.15” set for the pierce height. But then I allow the program to start cutting and again pause and the torch height is greater than the 0.06” cut height that was set based on the cut charts? Is it because THC has adjusted the height? According to the manual if using SMART voltage then if the IHS set the cut height to 0.06” the THC simply samples the arc voltage at that height and only moves to maintain that voltage which would suggest that the IHS did not move the torch to the 0.06” to begin with! ???

As I understand, initial cut height is set according to your program using the opening of the IHS switch as zero for the Z axis. If the material deflects or the IHS switch opens before contacting the material, this will trick the motion controller into a wrong initial height. If that is off, then I think it will affect the Smart Voltage setting and all your other heights. If you watch your THC traffic lights, you can see how fast all this happens. Pretty slick system.

I modified the g-code of one of my simple cut files so I could observe the initial torch motions as it gets ready to pierce and then cut. I removed the M3 that turns on the torch and inserted a pause command of 10 seconds between the G38.2, G38.4, the G0 commands that adjusted the torch height to compensate for IHS backlash and spring back and then the pierce height and cut height. These 10 sec pauses allowed me to accurately measure the torch to plate distances. It has been an interesting exercise and I plan on actually doing a YouTube video of the process along with an in-depth look at the THC process as well. Previously I just set pierce and cut height and let IHS and THC do their thing and the majority of the time it performs flawlessly. However, the little exercise has identified some conditions that result in the pierce and cut heights being 0.04” to high plus I want to play with the cut chart voltages and compare the cut results to using the SMART voltage system.

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