Learn/GcodePilot/Automation & safety
AVTHC Auto-Tune
Updated v2.4.9At a glance
- Self-calibrates arc voltage: samples what the arc really measures at true cut height, right after every touch-off
- Walks the target onto the measured value a few volts per pierce — no lurching, bounded total correction
- Settled? It offers to write the calibrated voltage into the cut chart — with a per-machine Always option
- Calibrated chart rows carry a note and a one-click Revert to factory
- Corrections are learned per machine, per chart row — 3/16 mild steel never leaks onto your 1/4 chart
- Manual ±1 V nudges mid-cut are adopted, not fought
The cut chart's voltage assumes a perfect measurement chain. A real machine reads arc voltage through a divider built from tolerance resistors, an ADC that is never perfectly linear, and a scale and offset set by hand — any error in that chain and the THC holds the wrong physical height while the readout looks correct. That height error is cut bevel, and diagnosing it from arc physics is one of the hardest things to teach a new operator.
Auto-Tune closes the loop from data instead. Right after every touch-off the torch descends to the commanded cut height — for that moment, height is ground truth. Auto-Tune samples what the arc voltage actually reads right there, at full cut speed, before the height control makes its first correction, and rejects everything else: the pierce spike, the settling arc after the descent, corner slowdowns, cuts too short to give a clean reading. Each pierce then nudges the AVTHC target a fraction of the measured error, so the correction sneaks onto the true value over two or three touch-offs.
Turning it on
Auto-Tune is opt-in, per machine: AVTHC pill → label dropdown → Auto-Tune… → enable. The pill shows a small AT chip while armed (solid while actively tuning a run). Pick a response — Gentle / Standard / Aggressive — or open Advanced for the raw numbers: gain, max step per cut, total authority, deadband, and how many settled cuts count as converged.
It needs a program posted with the current FluidNC plasma post, which stamps the cut-chart identity into the program header — that is how a running program knows which chart row it came from.
Writing the chart
When a run finishes settled, Auto-Tune offers to update the cut chart row to the calibrated voltage — accept and every future post of that material and thickness cuts at the right height with Auto-Tune off entirely. An Always update cut charts on this machine option makes future updates silent, each announced by a toast; uncheck it anytime in the Auto-Tune dialog. Calibrated rows show a note in the Cut Charts browser — when it was set and what it replaced — with one-click Revert to the factory value. Editing the voltage by hand clears the note, and locked chart sets are never written.
Corrections are learned per machine, per chart row, persist across restarts, and re-apply from the first pierce of the next program posted from that row. Once two or more thicknesses have settled, the dialog also shows the implied scale/offset error of the machine's voltage measurement — the root cause — so it can be fixed once in the THC config for every chart at once.
While it runs
The operator stays in charge. Manual ±1 V nudges on the AVTHC pill are adopted into the correction rather than fought, pausing suspends sampling, and disabling AVTHC stops actuation entirely. Every adjustment is logged to the console with the sampled voltage and the resulting target.