Arc Voltage measured value is displayed on the myCNC main screen. Arc voltage signal should be connected to the proper ADC input number. The number should be set up in THC configuration dialog.
Connect the test signal (for example 24V from test power source) to THC ADC input and check the voltage value displayed. Test signal should be connected through Arc Voltage Divider you use (not directly to the board ADC input).
If you don't see any voltage on the display, then
Current ratio is “0.1” (on the screen above), so total ratio would be
Now it's a good time to check default THC/PID settings
This is just default values you can start playing with on the screenshot above. “Recommended” values depend on machine speed, sheet thickness, plasma power source and torch type.
"Alarm Arc Voltage difference..." and "Alarm Arc Voltage Rise" settings help to prevent the torch diving while moving through the cut, on low speed corners etc. However, if the reference voltage is very different from the real measured voltage (more than these values), Height control may not start at all. You may want to temporarily set these values to "1000" to disable this feature and test the THC.
THC PI-control ratios may vary depends on a sheet thickness and plasma power source type. The higher P-ratios absolute values, the higher Height Control Speed. According to our experience, I-ratios should be set to "-2...-6". Higher I-ratio values may lead to oscillation during height control. Both P- and I-ratios should be NEGATIVE for Arc Voltage Height Control. This means - The higher Arc Voltage (if compare with reference position), The Lower should be Position.
The next step is to check if THC is ON in user settings.
If you don't have a recommended Reference Arc Volatge value tables from power source manufacturer (Cur Charts), you may need to find a good reference arc voltage value. To find it
Turn On back the THC in User settings and make test cutting.
That's all about THC Height control troubleshooting. The article might be updated in case we get some customers feedback.
|GVAR_THC0_ARC_VOLTAGE_REF||7011||Arc Voltage Reference value. This register is written while Load Cutcharts. It can be updated automatically if THC is activated in “Measure” mode. In this case, after THC activated and given “THC delay” controller measures real Arc Voltage, save this value as “Arc Reference” and keeps this value during the cut. Rotary encoder can be connected to this register to implement on-the-fly Arc Voltage adjustment|
|GVAR_THC0_ARC_VOLTAGE_ADJ||7012||Adjustment Value for Reference Arc. Either potentiometer or rotary encoder can be connected to this register to be able to adjust Arc Voltage reference on the fly VolategArc Voltage Reference value.|
|GVAR_THC0_ARC_VOLTAGE_REF2||7013||Register contains sum of Arc Voltage Reference register (#7011) and Adjustment register (#7012). The software automatically updates register value if any of register 7011,7012 is changed. The register is available for reading to display adjusted Arc Voltage reference value|