THC(9)

NAME
thc - Torch Height Control

SYNOPSIS

loadrt thc

DESCRIPTION

  Torch Height Control

Mesa THC > Encoder > LinuxCNC THC component

The Mesa THC sends a frequency based on the voltage detected to the encoder. The velocity from the encoder is converted to volts with the velocity scale parameter inside the THC component.

The THCAD card sends a frequency at 0 volts so the scale offset parameter is used to zero the calculated voltage.

  Component Functions

If enabled and torch is on and X + Y velocity is within tolerance of set speed allow the THC to offset the Z axis as needed to maintain voltage.

If enabled and torch is off and the Z axis is moving up remove any correction at a rate not to exceed the rate of movement of the Z axis.

If enabled and torch is off and there is no correction pass the Z position and feed back untouched.

If not enabled pass the Z position and feed back untouched.

  Physical Connections

Plasma Torch Arc Voltage Signal ⇒ 6 x 487k 1% resistors ⇒ THC Arc Voltage In

THC Frequency Signal ⇒ Encoder #0, pin A (Input)

Plasma Torch Arc OK Signal ⇒ input pin

output pin ⇒ Plasma Torch Start Arc Contacts

  HAL Plasma Connections

encoder.nn.velocity ⇒ thc.encoder-vel (tip voltage)

spindle.0.on ⇒ output pin (start the arc)

thc.arc-ok ⇐ motion.digital-in-00 ⇐ input pin (arc ok signal)

  HAL Motion Connections

thc.requested-vel ⇐ motion.requested-vel

thc.current-vel ⇐ motion.current-vel

FUNCTIONS

thc.- (requires a floating-point thread)

PINS

thc.encoder-vel float in
    Connect to hm2_5i20.0.encoder.00.velocity

thc.current-vel float in
    Connect to motion.current-vel

thc.requested-vel float in
    Connect to motion.requested-vel

thc.volts-requested float in
    Tip Volts current_vel >= min_velocity requested

thc.vel-tol float in
    Velocity Tolerance (Corner Lock)

thc.torch-on bit in
    Connect to spindle.N.on

thc.arc-ok bit in
    Arc OK from Plasma Torch

thc.enable bit in
    Enable the THC, if not enabled Z position is passed through

thc.z-pos-in float in
    Z Motor Position Command in from axis.n.motor-pos-cmd

thc.z-pos-out float out
    Z Motor Position Command Out

thc.z-fb-out float out
    Z Position Feedback to Axis

thc.volts float out
    The Calculated Volts

thc.vel-status bit out
    When the THC thinks we are at requested speed

thc.offset-value float out
    The Current Offset

PARAMETERS

thc.vel-scale float rw
    The scale to convert the Velocity signal to Volts

thc.scale-offset float rw
    The offset of the velocity input at 0 volts

thc.velocity-tol float rw
    The deviation percent from planned velocity

thc.voltage-tol float rw
    The deviation of Tip Voltage before correction takes place

thc.correction-vel float rw
    The amount of change in user units per period to move Z to correct

AUTHOR

John Thornton

LICENSE

GPLv2 or greater