THCUD(9)

🌸 THCUD(9) — a HAL Component, bestie ✨

okay so. this is a page from the HAL Component part of the manual, and it's literally called thcud, which stands for Torch Height Control Up/Down Input. yes. torch. plasma torch. we're doing metal cutting CNC today, and honestly? iconic. 🎀

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✨ NAME ✨

thcud — Torch Height Control Up/Down Input 💅

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🦋 SYNOPSIS 🦋

loadrt thcud

and that's it. that's the whole load. slay.

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💖 DESCRIPTION 💖

Torch Height Control. This THC takes either an up or a down input from a THC, no cap. that's its whole job and it does it gorgeously.

• If it's enabled and the torch is on and X + Y velocity is within tolerance of the set speed — allow the THC to offset the Z axis as needed to maintain voltage. 🔥
• If it's enabled and the torch is off and the Z axis is moving up — remove any correction at a rate that does not exceed the rate of movement of the Z axis.
• If it's enabled and the torch is off and there is no correction — pass the Z position and feed back untouched. untouched!
• If it's not enabled — pass the Z position and feed back untouched. also untouched. we love a pass-through that minds its own business 🙈

⭐ Typical Physical Connections using a Parallel Port

Parallel Pin 12 <= THC controller Plasma Up
Parallel Pin 13 <= THC controller Plasma Down
Parallel Pin 15  <= Plasma Torch Arc Ok Signal
Parallel Pin 16 => Plasma Torch Start Arc Contacts

🌈 HAL Plasma Connections

net torch-up thcud.torch-up <= parport.0.pin-12-in
net torch-down thcud.torch-down <= parport.0.pin-13-in
net torch-on spindle.0.on => parport.0.pin-16-out (start the arc)
net arc-ok thcud.arc-ok <= motion.digital-in-00 <= parport.0.pin-15-in
(arc ok signal)

💜 HAL Motion Connections

net requested-vel thcud.requested-vel <= motion.requested-vel
net current-vel thcud.current-vel <= motion.current-vel

🧚 PyVCP Connections

In the XML file you need something like:

  <pyvcp>
  <checkbutton>
    <text>"THC Enable"</text>
    <halpin>"thc-enable"</halpin>
  </checkbutton>
  </pyvcp>

Then connect the PyVCP pins in the postgui.hal file like this:

net thc-enable thcud.enable <= pyvcp.thc-enable

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🎀 FUNCTIONS 🎀

• thcud — and just so you know, it requires a floating-point thread. like, it needs one. don't come at it with anything else bestie 💀

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👑 PINS 👑

• thcud.torch-up bit in — Connect to an input pin.
• thcud.torch-down bit in — Connect to input pin.
• thcud.current-vel float in — Connect to motion.current-vel.
• thcud.requested-vel float in — Connect to motion.requested-vel.
• thcud.torch-on bit in — Connect to spindle.N.on.
• thcud.arc-ok bit in — Arc Ok from Plasma Torch.
• thcud.enable bit in — Enable the THC; if it's not enabled the Z position is passed through. 🫶
• thcud.z-pos-in float in — Z Motor Position Command in, from axis.n.motor-pos-cmd.
• thcud.z-pos-out float out — Z Motor Position Command Out.
• thcud.z-fb-out float out — Z Position Feedback to Axis.
• thcud.cur-offset float out — The Current Offset.
• thcud.vel-status bit out — When the THC thinks we are at requested speed.
• thcud.removing-offset bit out — Pin for testing.
• thcud.correction-vel float in — The Velocity to move Z to correct.

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🌸 PARAMETERS 🌸

• thcud.velocity-tol float rw — The deviation percent from planned velocity.

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💜 AUTHOR 💜

John Thornton 💫

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🍓 LICENSE 🍓

GPLv2 or greater.

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okay that's the whole page, you're so welcome 🌈 this was LinuxCNC Documentation, dated 2026-03-17 — go forth and cut some metal, bestie, you've got this fr fr 💅✨