General Question about THC operation

[4SCS]

Hello,

I have a quick question about torch height controllers.

I understand that many controllers will set a zero position either through an ohmic sensor or through the use of a float switch. My question is how does the THC know when to set the zero and how does it pause the gcode program from operating while it performs the movements to set the zero position?

Thanks for any help in understanding this.

[acourtjester]

When you generate a G-code using a post processor, it will have the instructions to add to the g-code for either. It is uses the Ohmic sensor the command will be (most likely) a g31 with a Z axis length like G31 Z0.5 f 25. The G31 is a probe command and the controller will wait for this to complete before moving back to the pierce height. The same is for a floating head switch but the command is G28, the main difference is the correction for the switch offset is also in the G-code. This is similar to the use of a THC the post processor will need to be setup to add this correct instructions in the G-code. So you know the THC has nothing to do with the Ohmic sensor or floating head switch.
The THC only comes into play after the torch has fired (m3 or other command). There generally is a delay after the torch fires (1. to 1.5 seconds) before the THC starts to watch the arc voltage, it is so the arc is stabilized (constant level).