THC and FireControl auto setting cut height

OK…as a total noob I have been cutting great over the last couple of months.
I had thought that THC with FireControl was setting my torch cutting height properly.

so I decided to do some measurements…
I programmed in to FC and cut along the Y axis to the right…
cut length 5 in
cut speed 95
IHS on
PD .3

Table starts…THC drops down sets torch height…and the cut starts…

I pause the cut in mid line…shut down the torch and measure the distance to between the torch and the metal…0.2…not the .06 as required…

why is this not at .06?

what have I done wrong?

Deflection possibly. I just started holding my 18 gauge down after seeing the torch riding on the surface. There was enough deflection on IHS that it wasn’t piercing or cutting at the ideal height.

I’d like to have my next machine be ohmic sensing, or do the mod that @TomWS did. I think it was him.

This could also be a result of ground interference. Is you computer plugged into a grounded socket while you are cutting? This will jack your live voltage and torch will raise to cut. I was an idiot and didnt catch on until my torch was cutting 1/4 plate about .5 from the surface. It’s not as noticeable on the thin stuff but when you cut thicker it’s very obvious.

Yeah, that’s a problem if your THC senses the voltage assuming that the torch is at the correct cut height when the measurement takes place. If it’s thin material even the air flow from the torch will deflect it. Before I installed my 'poor man’s ohmic sensor, the weight of the torch could easily deflect thin material greater than a reliable pierce height and the system would try to pierce with the torch literally sitting on the material.

I like the THC where you set the target voltage rather than sense it. This way, even if the material is deflected the THC will quickly bring it to the correct cutting height.

My cuts today were much better holding material down. Lots of movement in 18 gauge.

The clips in this thread Clamping down material - binder clips! work pretty well and they’re easy to make.

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Yeah I remember those. The file I’m cutting is pretty detailed though so it’s popping in the middle, and I’m working with full sheets. It’s not as bad after I resurface the slats. My final excuse is 18 gauge is thin, but not thin enough that I think those binder clips will help.

I have a plan to cut some strips of 1/2 sheet to frame projects like this while they are on the table.

Yeah, that’s a problem. Cut ordering might help. One thing I have done is place a 12x12 sample of Engineered stone countertop on the workpiece to weigh it down. If need be you can insert M1s in the code to allow you to move the weight around as you’re progressing.

I’ve used the clips on 16 ga that had some thin traces so tended to warp and the clips worked well. They’re great on 20ga.

I am guilty of taking threads off track…I will try to get his one back on track…

I will explain again…

cutting 1/8" plate steel…no warps
straight line cut option in FC
THC is either on or off…makes no differance.
IHS is on
no matter the settings in the line cut the torch head is .2 above the work…never the .06 it should be.

Obviously this is a FC problem as I have nothing to set for TH when you do a straight cut.

is there a way to correct this?

@toolboy Were you able to find a solution to this problem? I’m experiencing something similar and not on thin stock.

there are a few things here i have learned over the last year…
1 there is a setting in sheetcam for torch height…so by doing what I did in the beginning and stopping a cut midway I measured the cut height and then adjusted the setting in sheetcam …