Cut height problems

In tracking down some bevel issues, I took the advice of this forum and measured my cut height (paused mid cut). It’s high … around .125". I’m only using F360 with the 1.6 post processor (and latest version of firecontrol) which produced the following gcode:

G90 G94

(2D Profile1)
G0 X0. Y0.1012
G92 Z0.
G38.2 Z-5. F100.
G38.4 Z0.5 F20.
G92 Z0.
G0 Z0.04 (IHS Springback + Backlash)
G92 Z0.
G0 Z0.15 (Pierce Height)
G4 P0.5
G0 Z0.06 (Cut Height)
G1 Y0.0337 F63.
G1 X10.375 F63.
G0 Z1.


I have also verified the following:

  • torch tip reaches top of slats (plenty of Z-axis movement)
  • cut sequence looks normal (ihs hits the plate, z rises and pierces, and then z lowers for the cut
  • same result with THC on or off
  • changing IHS springback and cut height values in the post processing do change the z axis height during the cut, but I can never achieve 0.06"
  • ground clamp on work piece

Anyone have any other thoughts?

Thanks - Dig

Are you using smart voltage or setting a nominal voltage?

After torch goes to pierce height and pierces, does it drop to cut height and then rise up or does it just never go down?

I’m using smart voltage. I’m not sure how much of the initial IHS + pierce height + cut height is based on voltage or mechanical inputs.

I’ve tried the process several times and the readings are consistent. Everything just appears to be offset by some value - I believe the cut height stays consistent throughout the cut.

Quick followup question. Is the cutting height supposed to be the summation of the springback + backlash + cut height? In other words, should I be measuring my cut height at the tip to be 0.1" instead of the programmed value of 0.06"?

Yes,. But you will need to adjust spring back and backlash depending on you machine and material. I had to adjust my cut hieght to .05,. And spring back to 0 to achieve and actual cut hieght of .06

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No. Your cut height should measure .06", if that is where you set it. Here is an explanation of how the IHS system works:

G92 Z0. (set Z zero at the current position)
G38.2 Z-5.0 F100.0 (lower the torch up to 5" until the IHS switch opens)
G38.4 Z0.5 F20.0 (raise the torch up to .5" until the IHS switch closes)
G92 Z0.0 (set the current height as the new Z zero)
G0 Z0.02 (IHS Backlash) (raise the torch .02" to account for backlash)
G92 Z0.0 (set the current height as the new Z zero)
G0 Z0.15 (Pierce Height) (raise to .15" pierce height)
M3 (torch on)
G4 P0.5 (pierce delay .5 seconds)
G1 Z0.05 F100.0 (Cut Height) (lower to cut height of .06")

Backlash is a constant thing until there is additional wear on the system.
Springback is going to be different for different metal thicknesses and some won’t have any springback.

If you can’t reduce the excess torch height by eliminating the Blacklash and Springback, the only other option is to reduce your programmed cut height to achieve the desired actual height.

For example: If you have set your Springback and Backlash to zero and you are still getting a measured height of .09", you would have to reduce your programmed cut height to .03" to get an actual height of .06"

Is this line correct? Wouldn’t the cut height be 0.05"? I’m a gcode novice but trying to learn.

Sorry, I copied that from one of my files that had the cut height at .05". I wasn’t paying attention to the actual value that was there.

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Hey, no problem and thanks for the help - I’m having to dive in and learn the system at a new level. And thanks to all of the other repliers as I close this out.

For future searchers, I want to leave this snippet I found just a bit ago from langmuir-mike in another thread.

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