Do CF Pro do Ohmic (or floating head) material sensing?

I been looking around and can’t find out how the Fire Control or the CF Pro in general does material sensing. I see plenty of videos showing the THC bringing the torch down to contact the material, but I haven’t found any details how the machine/control/software is actually accomplishing this.

I have been assuming it did either some kind of 1) limit switch (floating head sensing) thing built into the THC mechanism or an option for ohmic sensing.

So how does Langmuir tackle it? I’m really hoping I can wire up ohmic sensing because it seems the most sensitive & accurate, and doesn’t cost much to do (I’m getting a Duramax65, so the option is dead simple).

I can run wires and even figure out whatever circuitry is needed for connecting things. But I’d kinda like to know ahead of time so I can have it all worked out before my machine arrives.

Thanks for any replies.

Limit switch. It touches the material firmly enough to to move it depending on the thickness. Not ohmic.


OK, dummy me. I finally got the bright idea to look at the assembly manual and finally found that the THC mechanism has a N.C. switch to be the sensor. That probably works pretty well, but I think I’d prefer to have ohmic sensing, so I’m gonna look into that. I might need to put together some kind of simple circuit so that kind of sensing is more solid & reliable (and not inverted), but I imagine I can just use it as-is for a little while before changing stuff up.
I dunno yet, but it seems like the ohmic sensing might be good to take advantage of eventually, and it should be a pretty simple circuit to match it to what the control is looking for.

A floating Z sense works well, is simple and reliable IF the material doesn’t flex too much under the pressure of the torch touching down. Thinner materials or highly warped material will be a problem.

Ohmic sensing, on the other hand, does work well in those circumstances, but has its own drawbacks, namely if you happen to get a lot of splash and the circuit is too sensitive, then you’ll get false reads as the probe lowers. It’s also expensive and may be inaccurate if the probe isn’t perfectly aligned with the tip (it also gets in the way when you replace consumables).

There haven’t been too many successful DIY Ohmic sensing posts on this forum that I recall. A few people use proximity sensors to detect touch down, but the problem there is that you need to surround the torch with more than one probe (what if that one probe is positioned over an already cutout section?).

Net: Play with what you have for a while and then study up on alternatives. Don’t try to get ‘perfect’ right away, it will elude you.

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Sounds like a challenge…
I’m in! :smiley:

I agree. I’ll just use it out of the box for a while and experiment some as I go. I’m not a whiz, but I have a few tools and a little meager knowledge. If it goes well enough, maybe I can contribute to helping some.

A guy can do so much with microcontrollers (if necessary) & simple electronics for dirt cheap these days. Seems like it oughtta be doable.

@Cletus, looks like you have a new friend.


No, this won’t work. Far too neat to do anything useful (or destructive)!

On the other hand, this could be fun! :rofl:

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I agree with brownfox…cletus is another mad scientist you may want to reach out to…
TomWS is also one of the smartest guys I know…here…

Oh oh, the rest of y’all just got partially insulted!

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corrected my post as I missed the “of” …one of the…not the smartest…

Well at least in my case, I already know I’m not smart. But I am too willing to dig in and tear shtuff apart, so there’s that.
Been doing a little studying up on sensing. I’m thinking there’s gotta be a way to bake in some amplifier kind of thing through some filter threshold and send out a reliable on/off. I wonder if an AC signal through the ohmic hardware might be more apt to pick up a touch compared to just a DC voltage? (like if the material isn’t pristine or the like…)
Anyways, just kinda thinking out loud right now. I’ll likely have plenty of time to experiment. I just ordered my Hypertherm today. Possibly (probably?) a longer lead time on that than the CrossFire. Good thing I’m old and patient these days.

BTW, went Cadillac with the plasma - Powermax 65 with machine and manual torches, enough various consumables to last me a while. Could have gone bigger, but gotta stop somewhere (it’ll do), and I think any larger than that starts creating new problems to solve right out of the gate. More $$ than the CrossFire! but I think it will be worth it. If nothing else, lower probability of hardware problems. As a beginner, I’d like to have as less possible causal variables as possible since I’m sure there will be… trouble.

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IIRC, the Hypertherm has an Ohmic Sensor ‘cap’ that you can order, but @mechanic416 would know better than me.

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Yeah thanks.
I included some of those parts in my order so I’ll have something to work with. Not enough to have backups, but one set should be fine for just experimenting.
I did get the full usable range of nozzles & such for optimizing per material. Seems like that was probably worth splurging on.

Actually, I believe, the original, ‘official’ sensor IS AC coupled so that the DC Voltage of the plasma can be blocked.

That’s one of the reasons it’s so expensive, AC excitation, high voltage isolation, and some pretty good signal filters.

Mine isn’t that sophisticated, but it works and is cheap :grinning:

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Hmm interesting. My intuition wasn’t flat out wrong… this time. :smiley:
Now if only I knew how & why. Baby steps.

Actually one of my early thoughts (seems like just yesterday… oh yeah, because it was) was wondering if the sensing should be disconnected during cutting for safety to the circuitry. I guess the fancy ones use ohmic for crash detection too, but I was leaning toward a breakaway mount (since I’m a machinist by trade already) with possibly a separate sensor for that.

Anyways, I got plenty of time to think on that.

Mine only connects when sensing and disconnects otherwise.

WAY too neat. My shop is a total mess right now, with my business projects as well as a couple of my own. Building a “Rocket Grill” for the poolside! :rofl::rofl:
Have not tried ohmic sensing yet. My floating head and THC works so damned good! :grin: