Touch probe in Avid CRP800 control

Hello everyone. I’ve been toying around with an idea off and on to integrate a touch probe for basic reverse engineering of 2D (or even 3D) geometric parts. I am wondering if any of you have tried or implemented anything similar.

I’d like to have the ability to probe an entire part face and build a point-cloud (in the case of a 3 dimension face) or probe multiple features within a part to create a dimensioned drawing. Basically a (very) poor man’s version of a CMM.

I know this can be done through the generic versions of Mach4. The question is whether or not the OEM AvidCNC version of Mach4 retained that feature and if their control allows for it. Perhaps the solution will be as simple as installing a second version off Mach 4 on my computer with different setup? My control is the current CRP800 NEMA 34, PRO2448.

And, yes, I do realize there are tolerance consideration to a NEMA 34 belt driven machine.

Thank you in advance for your thoughts!

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I’ve never used the wizard for anything other than compensating for curved parts when engraving, but, I have a drewtronics probe and it works great for the purpose.

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I do a great deal of work with my S5000LED probe on the PRO60120. I write my own scripts though. I use Fusion 360 and point clouds a lot in my business.

What comes with Mach4 is worthless IMHO because it uses G31 moves with no contact which the ESS freaks and stops on and Warp9 will tell you is crazy dangerous. I agree 100%.

You can disable that functionality in ESS but I would advise NOT to unless you are real careful. I have an M code somewhere for that but it’s evil. I say do it right and stay safe.

Also, probes should always be NC because when they fail they fail open. That will save you some serious cash! Nothing like damaging a nice spindle over a probe failing. And they do fail. Like any switch they wear and they get bumped and bruised in general use. Kind of their purpose, right?

The NC probes will make the AvidCNC tool touchoff sensor incompatible if you put them on the same port. I have a full ATC with a retracting tool carousel and a tool length probe so I could make the jump to a NC probe easy-peezie.

I would recommend the NO probes if you don’t have an ATC. That way the AvidCNC tool touchoff sensor will still work. Just get a M12 splitter and remember to not leave the magnet and ground wire attached or things won’t work.

If you need more info I can find the time. I am not the smartest guy in the room but I have broken my fair share of tools so you don’t have too!

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Thank you for the reply, Subnoize! Just the kind of response I was looking for. I appreciate your offer for help. I am not ready to “roll up the sleeves” on this yet. When I decide to lift the lid on my control, I will reach out. Probably a mid-winter project for me when work travel slows down. I will probably add an M12 4-pin port to the control box for the probe so I don’t need to disconnect either the touch plate or the probe.

I work in the metalworking side of the industry and woodworking projects on the CNC is a hobby that is both relaxing and keeps my work side of the brain exercised. Because of that, my usage of my AVIDCNC sometimes strays outside the lines on what most are doing.

Never thought about a NO probe to use in conjunction with the AVID touch plate (I do not have an ATC). I use to use a popular European control on my AVID Pro CNC that was phenomenal for point-clouds and high speed look-ahead called EdingCNC. They don’t have very good representation in the US so I’ve moved on and purchased the AVID control running MACH4.

Thank you, again, for your reply.


Can you elaborate on this more? Are you saying that a NO probe makes the ESS freak out?


Can you elaborate on this more? Are you saying that a NO probe makes the ESS freak out?


Ok, sorry for the confusion: Normally open probes work fine with ESS and Mach4, full stop.

Personally, I prefer NC or Normally Closed probes because when they fail they fail open and stop the probing routine.

OK, so that is cleared up, what I was talking about are the probing routines that Newfangled includes with Mach4. Newfangled and Warp9 Ltd have different opinions about the G31 probe command.

Newfangled thinks that if you get to the end of a G31 and there is no contact, that is fine. Everything is as expected.

Warp9 Ltd’s ESS will throw an alarm signal and throws the e-stop.

As such, Newfangled’s Mach4 probing routines will all fail unless you turn off that function in ESS by doing the following;

local hregProbingFailureDisablesMach = mc.mcRegGetHandle(inst, string.format("ESS/Probing_Failure_Disables_Mach"))
mc.mcRegSetValue(hregProbingFailureDisablesMach , 0 )

Then, when you are finished running the probing routine you would turn that back on by doing the opposite. Setting it to 1.

I kind of agree with Warp9 on this but I can also understand why Newfangled does it. They want to poke around and stop if they bump into something. Which isn’t something you can do with the G01 command.

My solution was to turn the code above into an M code and issue it before I use the Mach4 probe routines and issue it again to turn it back on after I am finished.

PS. All of my custom probing routines use the Warp9 interpretation of G31.

For further context on Newfangled and Warp9’s interpretation of G31 see the section titled “Mach4’s built in probing wizard (or utility or button) isn’t working right!”


You can write your own digitizer script and replace everything in that EdingCNC software. The key there is YOU. How much time do you want to spend on it. The provided Newfangled Mach4 scrips are “usable” but leave a lot to be desired. All of them can be replaced in a few weekends to be more usable for your particular needs.

A script to probe a defined area and save the points out to a CSV file for importing into apps like Fusion is pretty darn “entry level” programming.

That said, personally I find it much easier to use a cell phone and photogrammetry. If you take your time you can get really good results. The best part is you can capture in the field (or furniture store, lol). Here is a list of them;

That is what originally prompted my post. When I looked into point cloud probing a 3D surface, Newfangled and Warp9 conversations on the subject we almost complete opposed on the subject in CNCZone, etc.

Based on the complexity of accomplishing this in Mach4, I may just opt for a decent handheld scanner and just manually probing features for dimensions for 2D. Finding a Radii from 3 points would be a nice addition to the Wizard, however.

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It is a lot of work but not “impossible.” It is also terribly, terribly slow and the finest resolution being the little ball on the probe (about 1/8th inch is most common).

To be honest, the probe is a sensor for finding the stock and features on the stock for alignment and not really “digitizing models.”

If I could help you one last time, don’t buy any digitizer under $12k. You will be very disappointed. Spend the cash on a good app for your phone or PC.

The secret is your CNC machine’s accuracy and repeatability is less than what these apps will output with just a little practice.

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Sorry to barge into this thread but I have been struggling to get the drewtronics working, mind if I send you a message?

Not at all, Bill. Go ahead and post in my thread. I don’t have much to offer. I think ‘Subnoize’ was the one who referenced that??? Within the thread. Thank you for the courtesy of asking!!


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I love the little S5000LED, got two of them in fact. One for my metal mill and the other for my PRO60120.

If you need help ping me!

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Shopsabre offers a digital probe for reverse engineering. I have wondered how that works. Might be an option if it can be adapted.

Hi Bill,

Did you ever get your drewtronics working?

No I gave up and sold it. I reached out to Avid and the official support line was that they did not support those probes. I decided to shelf it at that point.

Funny you should ask though, I got bit in the butt this weekend with the edge finder on some not so great aluminum stock and now I am back to trying to figure out how I can get a “proper” probe working again…

Would love any pointers, especially pointers a total nebie like myself could follow :laughing:

I had mine working at one point for probing but haven’t been able to get the wiring worked out to get the LED to function as well. I have a AVID Pro4848, but with a custom ESS/Mach4 controller. I wired the probe into a different port on the BOB than the AVIS touchplate, but couldn’t figure out the resistor configuration using the built in power from the ESS Breakout Board port. IT bugged me that I could not get the probe and LED to function simultaneously, so I have mothballed it…

I was hoping someone had more luck than I did.

That is exactly the steps I took and basically where I ended up, lights not making sense, I could get one good probing run but the next running would plunge the probe tip into the stock, I started using cardboard boxes for testing to keep from blowing up more tips.

@subnoize says he has some working but he is way smarter than me and I can’t follow is tips :laughing:

I am really sorry to hear you guys are having trouble with the Drewtronics probe.

Again, I offer my help getting it sorted out if you want.

Just remember you CANNOT use the Avid touch-off scripts with it. The Avid script is hard-coded to do a G43 H1 and that causes problems. So you cannot use the tool table offsets with the Avid scripts.

The LED not working is probably the fact your controller isn’t a sinking input (or I might have that backwards, trust but verify :wink: ). But you can fix that with a resistor in a pull-up configuration to either 5 v or 10 v.

My offer stands. I actually have a Drewtronics probe on all of my machines now. The hardest was the old X3:machine which required the pull-up resistor. 5 v is a little low so the LED is dim but it works.

Thanks subnoize… I have to dust off my notes on what I have done and wire the probe up again. It’s been a couple of years since my last go at it.

Are the base Mach4 probe routines usable? I don’t use the AVID Mach4 installation.