THC

NAME
SYNOPSIS
DESCRIPTION
FUNCTIONS
PINS
PARAMETERS
AUTHOR
LICENSE

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)
motion.spindle-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 motion.spindle-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