IHC & THC doing crazy things

Been cutting steel and aluminum with no problem on one cut. start to do a second cut on either material and the IHC alarm comes up after a minute then the THC alarm comes up. Reset the cut path and the z axis does not want to contact the plate. cleaned everything on the Z axis, adjusted the roller bearing, no issues with cables or wiring.
I am at a lost for this issue. wasted several pieces of material. Please advise if you can help.


How high is the torch mounted. Drop the red piece that holds the torch down some.

How close does it get? Can you post pictures of how it is mounted?

When you say IHC alarm are you talking about the green lit IHS at the bottom of the FireControl screen?

And when you say the THC alarm comes up are you saying the the lights of THC are flashing on/off?:
THC lights

Because if you are seeing the IHS light turn green on the bottom of the screen, it is indicating that the IHS switch has lost connection either by the torch touching down or a faulty/dirty connection.

If the torch is, indeed, touching the plate, then THC will sense the decrease of voltage and then raise the torch to get back to a height that has the proper voltage.

You might hit the spacebar during one such cut and measure your torch height with a feeler gauge. If you don’t have a feeler gauge, a piece of 16 gauge metal is a close approximation (thank you Don!).

That could be because it already thinks you are touching the plate: connection of the IHS switch is lost either by the dirty or damaged contact. Or a wire is broken and not connected well. Check the connection going into the z-axis at the enclosure. Pull the wire from the IHS at the enclosure and test connectivity to the switch contacts in the z-axis assembly. You will need to push the torch up to expose the contact points.

Phillip has some good points and concerns as well. Please respond to him.

I’m guessing that it’s the Z axis lead screw coupler slipping.

The IHS sequence includes a command to probe down, up to 5 inches or until the IHS switch opens.

That message indicates that Firecontrol thinks the Z axis has traveled 5 inches and has not opened the IHS switch.

The only way for that to happen, is the coupler is slipping. This allows the motor to turn enough steps to travel 5", but that movement is not being transferred to the lead screw.


David, you amaze me every time you respond here. You really know your stuff. That makes a lot of sense.

@GlennPetti The screen grabs of the messages are very helpful. Thank you.