Z Axis bobbing up and down

Z axis bobbing up and down IHS switch is clean and dry only does this with THC activated at my witts end have any ideas?

You are either hunting voltage or the ihs switch keeps tripping.

When it does these does the ihs light turn on and off in fire control?

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If you see these lights quickly changing as it is doing the bobbing then you know it is something with the THC.

If it is these lights then try entering nominal voltage into the settings for THC Control. Click on SETTINGS to set “Nominal” Voltage. Any number in the Nominal Voltage tab other than 0.0 turns off the SMARTVoltage.

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I am thinking torch is mounted too high. When it reaches cut height ihs trips making it raise. Then it trys to go to cut height again

Ok,Lowered the torch it wasn’t too high but lowered it anyway the Active and Down lights are flashing and so is the IHS flashing so i stopped the cut and checked the cut height with feeler gauges it is right at .060. The VIR was replaced about a month ago under warranty even thou my machine over 3 years old.The THC problems have been the only problem i have ever had.With the THC off the cuts great little dross i have no complaints except for this.

The ihs light coming on is you bobbing issue. Just need to find out why it is tripping or fire control thinks it is. When bobbing does the torch strick the material?

Can you post pictures of how your torch is mounted and of the ihs switch?

Have you had it apart for any reason?
Work clamp on the material?

Just need to cover all your bases.
Have you changed any of the THC settings? I changed the speed on mine then noticed it bobbing in radiuses where I had path rules set.


Torch is not touching the material which is right now i’m cutting 1/4" platenever been aoart all connections and wiring has been tested and cleaned which THC settings are you refering too?

You click on the settings button in the thc section. I assume you have not changed them.

You say tested and cleaned. Have you made sure you don’t have a loose connection. I had that happen to me before.
Just to make sure if you wiggle the torch by hand does the ihs light come on?
Not saying you don’t have your torch adjusted right this is how I do when I take mine apart. I will move the z until the ihs light come on then mount the torch about a half inch below the top of the slates.


Yes. Phillip has this right.

That light should only come on when the torch hits the metal and causes the z-axis to float up. If that occurs during the cut and the contacts are not losing physical contact then you likely have a loose connection, broken wire, dirt/silicone on contact surfaces or there is tension on the torch cable coming off the overhead cable support of the table that pulls the torch up a bit.


Langmuir has suggested if you get bobbing that increasing the sample size in the THC settings will soften/delay/limit (not sure the word they used :crazy_face:) the reaction of THC. But the fact that you have the IHS light come on, that is like an alarm for the cutting process. You have to fix that before you want to mess with the THC settings, IMO.

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Ok let work on that and i will get back to you.Thanks

Check the IHC contact to see if tang is pushed into the Z axis screw, will make things do whacky stuff if it is… Don’t want tang touching z axis screw.


Took the Z axis apart and cleaned didn’t see any issues.Tang not hitting.

Look over your IHS wires for possible bare spot-on wires, follow wires back to control box. If wires short can give false IHC reading.

Everything electrical is ok