Voltage Scale and Auto Volts

You can do the following to achieve this but you are really only masking the issue.

In the [DISPLAY] section of the ini file add a new variable:
Create a new file in the config directory named custom_code.py

Have the following in the custom_code.py file:
The second line is optional and is only used to step 0.1 at a time with the arrow buttons.

Hi Phil,

Thank you for that. I might be masking an issue, but setting the Speed (PID-I) at 0.1 enabled me to see what is happening.

I am cutting 25mm steel at 125A, feedrate 610mm/min. Voltage hovers around 110 Volts (Hypertherm 125 manaual says it should be 169, but it cuts alright at this voltage, don't know why). I pierce the material first to remove dross. Then start cutting, and at some point the Z-axis slowly starts moving up (it used to do this rapidly with Speed (PID-I) at 10. I can see the voltage steadily drop to 100 Volts, but the THC is not correcting, the Z-axis just keeps lifting the torch up until of course it loses arc.

The configuration I use for cutting thick plate has all of everybody's recommendations, lowered accelerations as per Tommy's suggestion etc. I have also rechecked all the wiring, moved the THCAD away from power sources to avoid interference etc. Parameter settings are 4 seconds for THC delay (for the lower feedrate, gives the arc time to stabilize), THC Threshold 1 Volt, Speed (PID-P) 0.1 (to see what happens), VAD Threshold 80%, Void Override 80%, PID-I and PID-D both 0.

I am quite confident we can rule out Z-axis interference, I have used this configuration successfully to cut 12mm and 16mm steel without any hiccups, the THC worked just fine.

I do not know if other people cut much 25mm plate and maybe have suggestions ? Or are we the odd duck out here ? Mind you, if we disable the THC the machine cuts 25mm plate no worries, but the plate has to be exactly level on the bed. It would be just nice if we could find out why this gremlin occurs.

Cheers, Peter

Hmm, there certainly is some weird behaviour there.

Can you make a backup of your config from the parameters tab and post it.

EDIT: I re-read your post and you say that the voltage is falling as the torch is rising, I would have expected the opposite.
 

Hi Phil,

I have attached a backup of the config.

Well, exactly, we would expect to see the THC lowering the torch as the voltage drops, but instead it keeps moving up. I watched it again and I can see the Z-axis moving up, voltage drops a couple of volts but the THC is not correcting. That is what baffles us.

Cheers, Peter

phillc54 wrote:

EDIT: I re-read your post and you say that the voltage is falling as the torch is rising, I would have expected the opposite.

 

That is not the symptom, it is the cause.
The voltage is falling so the torch is raising to compensate.

Normally if the voltage drops then the torch is raised, which is what you are describing is happening. As the torch is raised the voltage should increase but because the voltage is falling THC is trying to raise the torch.