Change sheetcam IHS frequency

Hello all,

I am currently using sheetcam and a crossfire with the z axis upgrade and succesfully cutting using IHS/THC, no issues there. Cutting using FireControl. My one gripe is that IHS touches off before every single cut loop. The parts I make have many many starts and stops in a small area, and the IHS touch off adds a considerable amount of cutting time, I’d say almost doubles the cut time. Is there any way to reduce the frequency that IHS occurs?

Ideally, I would like to be able to set it so that IHS is distance based, I.E IHS touches off after the start location is X distance away from the last touch off. This would allow me to make a more reasonable touch off area, lets say a radius of 6" from last touch off. Worst case scenario, setting touch off to occur once out of every X cut loops would also help a lot. Is there any way to accomplish this?

I am using the defaul sheetcam langmuir post processor. Thanks in advance!

I am not aware of a work around you are wanting to do… that would be appealing but…given the fact that at times the metal crawls around and warps it seems you might create a cut quality problem if you were able to do that. If you are super confident of your material stability, you could just run with ihs off I believe.

You could edit the GCode file to remove the IHS sequences. I don’t know of any programmatic way of removing them. If you’re cutting thin material, you’ll really need each one of those to compensate for warp. If you’re cutting thick material, then, technically, you could get away with removing most of them.

You could also edit the PostProcessor code and make your own version that doesn’t do ANY IHS and then stick in a special operation in the beginning to do initial sensing.

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Understood, I am usually cutting 16 and 11ga with minimal warpage. I think removing the IHS from the post-process code and then inserting it between operations in sheetcam could work, I’m just not very fluent in editing gcode.

@langmuirsystems is there any precedent for something like this?

Here is the link to the documentation on the G-Code. Look on page 2 for the IHS sequence.

In the sequence:

G38.2 Z-5.000 F100.0 (Probe Seek Down)
G38.4 Z.5 F20.0 (Probe Seek Up)
G92 Z0.000 (Zero Z)
G0 Z0.15 (Move to Pierce Height)
M3 (Fire Torch)
G4 P0.4 (Pierce Delay)
G1 Z0.06 F100.0 (Move to Cut Height)
H1 (Enable THC Control)
G1 X0.6941 Y5.530 F129.0 (First line of Cut)

The first three lines can be removed to disable IHS…

Leave it in in the first block of code for initial calibration.


One more tip, in sheetcam, every time you have a new operation, you’ll get a header that starts with:

(Operation: ....)

If you separate the short cuts with their own operation you’ll be able to easily find just that block of code in your G-Code file and edit just those IHS cycles.

A useful tool for easily editing G-Code is Notepad++, it’s free and you can easily create a Macro to find ‘G38.2’, and delete 3 lines as a single operation.