thc − Torch Height Control
|
loadrt thc |
Torch Height Control Mesa THC > Mesa 5i20 Encoder > EMC THC 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. The THCAD card sends a frequency at 0 volts so the scale offset parameter is used to correct this.
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 => parport.0.pin-15-in parport.0.pin-16-out => Plasma Torch Start Arc Contacts
HAL Plasma Connections hm2_5i20.0.encoder.00.velocity => thc.encoder-vel (tip voltage) motion.spindle-on => parport.0.pin-16-out (start the arc) thc.arc-ok <= motion.digital-in-00 <= parport.0.pin-15-in (arc ok signal)
HAL Motion Connections thc.requested-vel <= motion.requested-vel thc.current-vel <= motion.current-vel
thc (requires a floating-point thread)
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_velocityequested (SP)
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.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
John Thornton
GPLv2 or greater