THC - TD Cutmaster 42

Ran across a weird issue tonight and was hoping someone might have seen this before.

I am using a TD Cutmaster 42 on a CF Pro Table. Because this machine is not CNC ready I did have to open it to wire up the torch control which was easy enough to splice into the wires before they plug into the board. I also had to attach leads to monitor raw voltage for THC. Again this was a simple connection to the work piece clamp (+) main lug and the torch (-) main lug with some ring connectors. After running test cuts I settled on 100V as the nominal voltage for 16ga steel (35amps, 125 IPM, .175 pierce, .125 cut height for the non shielded consumables on this machine)

This combination worked great for a few weeks until I ran into an issue with the THC continually raising because 100V could not be reached. I ended up setting the machine on smart voltage and watching it cut, it seemed that the machine was now running 78 volts with the same settings on the same material. I opened up the machine and verified all the connections are still tight.

Any idea what might cause this? On the plus side the smart voltage worked great on the 16ga but I am confused as to what is causing the sudden change in the voltage being read by the THC. I also swapped out all the consumables including the start cartridge and again the voltage was around 78-80 volts.

Are you using a different computer? A laptop that is now plugged into power? Has anything related to power changed in the system?

Same laptop, it is always plugged in (battery is no good, same outlet). No power changes, same wire routing as before.

I do need to make some test cuts with a multimeter hooked to the raw voltage plugs to verify that voltage value. I expect that to be different than what I am seeing in FireControl since the cut quality does not seem to have changed.

Any other things I should check?

Just wanted to follow up since I had a few minutes to run some tests today.

For reference the sheet from the last job that I ran using smart voltage was still on the table so I had no setup that had to be done for these tests.

I created a 8" by 2" rectangle to use for the test and posted to the machine with the same settings as before (16ga steel, 35amps, 125 IPM, .175 pierce, .125 cut height)

I ran three cuts with THC off and the leads plugged into a multimeter to check voltage.
All three ran ~100-108Volts (Sheet has some warping)

I hooked the two wires back up to the THC module and ran 6 more cuts with THC on set @ 100V. THC functioned perfectly and the read out in FireControl was spot on.

The good news is these test went well, the bad news is I have no idea what the “fix” was. I will continue to monitor as I keep running it but I am open to any speculation at this point.

Thanks!